Abstract
Rationale
Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by impaired social interaction and restricted/stereotyped behavior. Prenatal exposure to valproic acid (VPA) is associated with an increased risk of developing ASD in humans and autistic-like behaviors in rodents. Increasing evidence indicates that dysfunctions of glutamate receptors at synapses are associated with ASD. In the VPA rat model, an involvement of glutamate receptors in autism-like phenotypes has been suggested; however, few studies were carried out on metabotropic glutamate (mGlu) receptors.
Objectives
We examined the protein expression levels of group I (mGlu1 and mGlu5) and group II (mGlu2/3) mGlu receptors in rats prenatally exposed to VPA and evaluated the effect of mGlu receptor modulation on an early autism-like phenotype in these animals.
Methods
We used western blotting analysis on synaptosomes obtained from forebrain of control and VPA rats at different ages (postnatal day P13, 35, 90) and carried out ultrasonic vocalization (USV) emission test in infant control and VPA rats.
Results
The expression levels of all these receptors were significantly increased in infant VPA rats. No changes were detected in adolescent and adult rats. An acute treatment with the preferential mGlu2/3 antagonist, LY341495, attenuated the impairment in the USV emission in VPA rats. No effect was observed after a treatment with the mGlu5 selective antagonist, MTEP.
Conclusions
Our findings demonstrate that the expression of group I and group II mGlu receptors is upregulated at synapses of infant VPA rats and suggest that mGlu2/3 receptor modulation may have a therapeutic potential in ASD.
Similar content being viewed by others
Avoid common mistakes on your manuscript.
Introduction
Autism spectrum disorder (ASD) includes a group of clinically and genetically heterogeneous debilitating neurodevelopmental disorders commonly characterized by impaired social interaction and stereotyped behaviors (Lord et al. 2020). Patients frequently exhibit intellectual disability, epilepsy, attention deficit hyperactivity disorder, and anxiety. The underlying cause is mostly unknown while about 20% of cases have a genetic cause, including chromosomal rearrangements, copy number variations, or point mutations (Abrahams and Geschwind 2008). Exposure to environmental factors during pregnancy may also play an important role in the etiology of autism and can increase the risk of developing autism (for a review, see Sealey et al. 2016). Thus, a combination of genetic, epigenetic, and environmental factors is believed to play a role in the etiology of autism. The neurophysiological bases of ASD are still unclear. There is currently no drug therapy that targets the pathophysiological mechanisms underlying the core symptoms of autism. The pharmacological approach is mainly symptomatic, aimed at favoring more adequate and socially acceptable behaviors, or aimed at limiting associated manifestations in comorbidities.
Clinical studies reported that maternal use of valproic acid (VPA), a common antiepileptic drug and mood stabilizer (Löscher 2002), can affect fetal brain development during pregnancy and induce several abnormalities in the exposed children (Christensen et al. 2013). Prenatal VPA exposure is considered an environmental risk factor involved in the pathogenesis of ASD in humans, and rats prenatally exposed to VPA represent a validated experimental model of autism (Nicolini and Fahnestock 2018; Tartaglione et al. 2019). Nevertheless, the mechanisms by which VPA exposure induces autistic-like phenotypes are still not clear.
Several studies examined the receptor expression profiles in different genetic and environmental animal models of autism. Alterations and imbalance of several neurochemical systems seem to be involved in ASD pathophysiology (Rubenstein and Merzenich 2003). Patients with ASD, as well as animal models of the disease, show altered expression of synaptic proteins (Zoghbi and Bear 2012) and functional defects in excitatory or inhibitory neurons (Gao and Penzes 2015; Howell and Smith 2019). Glutamate is the major excitatory neurotransmitter in the brain and is involved in a wide range of physiological functions of the central nervous system. Its action is mediated by ionotropic and metabotropic glutamate (mGlu) receptors (Reiner and Levitz 2018). Ionotropic glutamate receptors are multimeric ion channels that mediate fast synaptic transmission and include N-methyl-D-aspartate (NMDA) receptors, α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptors, and kainate (KA) receptors (Traynelis et al. 2010). mGlu receptors are G protein-coupled receptors forming a family of eight subtypes (mGlu1 to mGlu8), of which mGlu1 and mGlu5 (group I) are coupled to Gq/11, and all other subtypes (mGlu2 and mGlu3, group II; mGlu4, mGlu6, mGlu7, mGlu8, group III) are coupled to Gi/o (Nicoletti et al. 2011). Growing evidence supports a role for mGlu receptor dysfunction in ASD (Nisar et al. 2022), and a disrupted mGlu receptor signaling, particularly mGlu5 receptor-mediated signaling, can be common to different forms of ASD (Bear et al. 2004; D’Antoni et al. 2014; Pignatelli et al. 2014; Petrelli and Bezzi 2018).
Changes in the expression of genes encoding proteins implicated in glutamatergic (excitatory) and GABAergic (inhibitory) neurotransmission and an excitatory/inhibitory imbalance were detected in VPA-exposed rats (Kim et al. 2014, 2016; Lenart et al. 2020). Alterations in synaptic transmission, connectivity, and synaptic plasticity have also been found in this animal model. VPA-exposed rats show an increase in glutamatergic activity (Tyzio et al. 2014) and in the long-term enhancement (LTP) of the thalamo-amygdala synapses (Lin et al. 2013), an altered expression of NMDA and AMPA ionotropic receptors (Rinaldi et al. 2007; Walcott et al. 2011; Martin and Manzoni 2014; Kim et al. 2016; Chau et al. 2017), and a dysregulation of the signal transduction pathways mediated by the activation of the ionotropic and metabotropic glutamate receptors (Kim et al. 2016, 2017). Compared to the numerous data on ionotropic glutamate receptors, few studies have been performed on mGlu receptors in this animal model (Chen et al. 2014; Peralta et al. 2016; Kim et al. 2016; Galineau et al. 2023).
In this work, we evaluated protein expression levels of group I and group II mGlu receptors in synaptosomes obtained from control and VPA-exposed rats at different ages. We observed an enhancement of both group I and group II mGlu receptor expressions in infant rats prenatally exposed to VPA and a correction of an early autism-like phenotype after systemic treatment with the preferential mGlu2/3 receptor antagonist LY341495.
Methods
Animals
We used Wistar rats (Charles River, Calco, Como). The female rats, arrived and housed in the animal facility, were mated with the males for a week. A vaginal smear was performed every day to check for sperm and evaluate the various phases of the estrous cycle. In the event of a positive outcome (presence of spermatozoa in the slide), the female rats were isolated from the male and placed inside new Makrolon cages (40 (length) × 26 (width) × 20 (height) cm), under controlled conditions (temperature 20–21 °C, 55–65% relative humidity, and 12/12 h light cycle with lights on at 07:00 h). Isolation day was considered gestational day 1 ( GD1). One day after birth (P1), the offspring were reduced to a number of 8 for each litter (2 females and 6 males). The animals were fed a standard diet, and food and water were made available ad libitum. Behavioral test was performed during the light phase of the cycle, between 10:00 and 15:00.
All procedures used comply with the guidelines dictated by the Italian Ministry of Health (Legislative Decree 26/2014) and by the European Community (Directive 2010/63/EU).
Drug administration
Valproic acid (VPA) (Cayman Chemical) was dissolved in saline at concentration of 250 mg/ml. At GD 12.5, pregnant rats were treated intraperitoneally with 500 mg/kg VPA, a dose that induces autistic-like behavioral changes in the rat offspring (Servadio et al. 2016; Melancia et al. 2018). Control dams were treated with saline (SAL) solution. The offspring prenatally exposed to either VPA or SAL were treated with LY341495 (Tocris), MTEP (Tocris), or their vehicle (saline solution, VEH). Intraperitoneal injections of saline, LY341495 (1 mg/kg), or MTEP (0.3 and 1 mg/kg) were performed 1 h before the behavioral test.
Synaptosome isolation
Frozen forebrains from control and VPA-exposed rats at postnatal day (P)13, P35, and P90 were allowed to thaw on ice, weighed, and homogenized in 10% (w/v) 0.32 M sucrose buffer containing ethylenediaminetetraacetic acid (EDTA 1 mM, Sigma), Tris–HCl (10 mM, pH 7.4, Sigma), phenylmethanesulfonyl fluoride (PMSF 0.5 mM, Sigma), and protease inhibitor cocktail (Roche). Nuclear fraction and cell debris were pelleted by centrifugation at 1000 × g for 10 min (4 °C). The supernatant was then centrifuged for 30 min at 10,000 × g (4 °C), and the resulting pellet was resuspended with the 0.32 M sucrose buffer, layered on top of discontinuous sucrose gradient (0.8, 1.0, and 1.2 M) and centrifuged for 2 h at 75,000 × g (4 °C). Synaptosomes were collected at the 1/1.2 M sucrose interface, diluted 1:2 in cold 0.32 M sucrose buffer, and pelleted (40,000 × g; 1 h; 4 °C). The pellets were resuspended in 40 mM Tris–HCl, pH 6.8, containing 0.5 mM PMSF and protease inhibitor cocktail. Protein concentration was calculated by BCA method (Pierce).
Western blot analysis
Proteins were denatured in denaturating sample buffer (2X) at 37 °C for 5 min, resolved through 7.5% SDS–polyacrylamide gels (Bio-Rad), and then transferred onto nitrocellulose membranes (Hybond-C Extra, 0.45 μM, Amersham Biosciences) with a trans-blot semi-dry transfer cell (Bio-Rad). Filters were processed as indicated by the manufacturer of WesternBreeze Chemiluminescent Immunodetection System kit (Invitrogen). In brief, filters were blocked for 30 min with blocking solution and then incubated overnight at 4 °C with the following primary antibodies: anti-mGlu1α (mouse, 1:1000, G209-488 BD Pharmingen), anti-mGlu5 (rabbit, 1:2000, ab76316 Abcam), anti mGlu2/3 (rabbit, 1:1000, AB1553 Chemicon), anti-mGlu3 (rabbit, 1:500, AGC-012 Alomone Lab), anti-mGlu3 (rabbit, 1:1000, ab140741 Abcam), anti-mGlu3 (rabbit, 1:100, sc-271899 Santa Cruz), anti-mGlu2 (rabbit, 1:500, AGC-011 Alomone Lab), anti-mGlu2 (rabbit, 1:1000, ab150387 Abcam), anti-pan Homer (H-311) (rabbit, 1:1000, sc-15321 Santa Cruz), anti-Homer 1a (goat, 1:1000, sc-8922 Santa Cruz), anti-Norbin (mouse, 1:700, ab88877 Abcam), anti-β-actin (8H10D10) (mouse, 1:1000, #3700 Cell Signaling), and anti-GFAP (mouse, 1:100, MAB360 Millipore). After washing with TBST (Tris (100 mM, Sigma), sodium chloride (NaCl, 0.9%, Sigma), and Tween 20 (1%, Sigma)), filters were incubated with alkaline phosphatase-conjugated secondary anti-rabbit antibodies from Invitrogen kit at room temperature. Chemiluminescence was detected and quantified by computer-assisted densitometry, using the VersaDoc 4000 Imaging System (Bio-Rad). Values were normalized to those of actin. For each protein of interest, four to eleven samples from different animals were used. Data are expressed as percentage of controls.
The specificity of anti-mGlu receptor antibodies was tested by using brain tissue from mice lacking mGlu1, mGlu2, mGlu3, and both mGlu2 and mGlu3 receptors, available at IRCCS Neuromed (Pozzilli, Italy).
Isolation‐induced ultrasonic vocalizations
On P9, the isolation‐induced ultrasonic vocalizations (USVs) emitted by each pup removed from the nest and placed into a Plexiglas arena were detected for 3 min by an ultrasound microphone (Avisoft Bioacoustics) sensitive to frequencies between 10 and 200 kHz. USVs were analyzed quantitatively using a Avisoft Recorder software (version 5.1).
Statistical analysis
GraphPad Prism 9.5 software (GraphPad Software) was used for the statistical analyses. Statistical significance was determined using Student’s t-test (for western blot experiments), or two-way ANOVA followed by Newman–Keuls post hoc test (for USV analysis). Student’s t-test was used to compare the levels of proteins expression between the VPA-exposed rats and their respective controls at each age. Statistical tests and results of statistical analyses are specified in each figure legend. All data are presented as mean ± SEM.
Results
mGlu1 and mGlu5 receptors are upregulated in the synapses of infant VPA-exposed rats
ASD is considered a synaptic disorder (Ebrahimi-Fakhari and Sahin 2015). Thus, we performed the experiments on synaptosomes obtained from the forebrain of control and VPA-exposed rats. To examine whether age-specific changes in mGlu receptor expression occur in rats prenatally exposed to VPA, we performed our analysis at P13, P35, and P90, which are considered equivalent to human infancy, adolescence, and adulthood. We used only male offspring, because in the VPA model, the autistic-like phenotype is more evident in male offspring (Melancia et al. 2018).
Western blot experiments showed an increase in mGlu1α receptor protein levels in the forebrain of VPA-exposed rats compared to their respective controls at P13 (Fig. 1a, d), whereas no changes between control and VPA-exposed rats were observed at P35 and P90 (Fig. 1b–d). Enhanced mGlu5 receptor protein levels could also be detected in VPA-exposed rats at P13, but not at later ages (Fig. 2) (see supplementary Fig. 1a for the specificity of anti-mGlu1α antibody). The specificity of anti mGlu5 antibodies has been previously tested using the cerebral cortex of mGlu5 knockout (KO) mice (Di Menna et al. 2023).
Several properties of mGlu5 receptors depend on their physical interaction with scaffolding proteins, including Homer proteins (Kammermeier et al. 2000; Ango et al. 2001; Park et al. 2008) and Norbin (Wang et al. 2009). To study whether altered levels of mGlu5 were associated with changes in these proteins, we evaluated the expression of Homer, Homer 1a, and Norbin at P13 but observed no differences between control and VPA rats (Fig. 3).
mGlu2/3 receptor expression is increased in synaptosomes of VPA-exposed rats at postnatal day 13
For the study of group II mGlu receptors, we first used an antibody that cannot distinguish between mGlu2 and mGlu3 receptors. We observed an increase in mGlu2/3 receptor protein levels in synaptosomes isolated from the forebrain of P13 male rats prenatally exposed to VPA (Fig. 4a, d). No differences were found between control and VPA-exposed rats at P35 and P90 (Fig. 4b–d). The specificity of the antibody was confirmed by western blot experiment performed on lysates of prefrontal cortex obtained from mGlu2/3 receptor KO mice. As shown in the supplementary Fig. 1b, the anti‐mGlu2/3 antibody failed to recognize the bands corresponding to mGlu2/3 monomers and dimers in lysates from mGlu2/3 KO mice.
To establish whether the increase could be ascribed to either mGlu2 or mGlu3 receptors, we decided to examine expression levels of the two receptors separately. We could not study the expression of mGlu2 receptors because the commercially available antibodies that we have used (Abcam and Alomone Lab) labeled nonspecific bands that were still present in lysates from mGlu2 receptor KO mice (Supplementary Figure 1c). For mGlu3 receptors, we used three different antibodies (supplied by Abcam, Alomone Lab, and Santa Cruz), and we evaluated their specificity in western blot analysis on cortical homogenates from mGlu3 KO mice. We observed a specific signal only with the Alomone Lab antibody (Supplementary Figure 1d). Using this antibody, we found a significant increase in the expression levels of the monomeric form of mGlu3 receptors in VPA-exposed rats at P13 (Fig. 5a, d). No differences were detected between control and VPA-exposed rats at P35 and P90 (Fig. 5b–d).
mGlu3 and mGlu5 receptors are highly expressed in glial cells (D’Antoni et al. 2008; Spampinato et al. 2018), and an increased number of GFAP positive astrocytes have been detected in the rat VPA model (Deckmann et al. 2021). Since a small amount of the astrocytic processes associated with synapses is present in our synaptosomal preparation, we investigated whether the increased expression of mGlu2/3 receptors found in VPA-exposed rats at P13 was associated with changes in GFAP levels. At this age, GFAP levels did not differ between VPA-exposed and control rats (Supplementary Figure 2).
Antagonism of mGlu2/3 receptors, but not mGlu5 receptors, corrects the reduced ultrasonic vocalization emission displayed by VPA-exposed infant rats
Evidence supports the use of mGlu2/3 and mGlu5 receptor modulators in the treatment of neurodevelopmental disorders (for a review, see Witkin et al. 2022). Thus, moving from the increased mGlu2/3 and mGlu5 protein levels found in VPA-exposed rats at P13, we decided to examine whether treatment with receptor antagonists could correct abnormal phenotypes of infant VPA-exposed rats. Socio-communicative symptoms were assessed through the ultrasonic vocalization (USV) test. In rodents, USVs play a fundamental role in mother–offspring interactions, as they induce maternal retrieval and elicit care giving behaviors in the dam (Servadio et al. 2015). We focused on mGlu5 and mGlu2/3 receptors because modulation of these receptors has been reported to correct repetitive behavior and social impairment in the VPA model (Mehta et al. 2011; Chen et al. 2014), while the effects of blocking the mGlu5 and mGlu2/3 receptors on USVs have not been examined. Control and VPA-exposed rats (P9) were treated 1 h before the test with MTEP (0.3 and 1 mg/kg), a selective negative allosteric modulator (NAM) of mGlu5 receptors. VPA-exposed male pups vocalized significantly less compared to the control group when isolated from the dam and siblings, as expected. A treatment with MTEP (1 mg/kg) caused a reduction of USVs in control rats (Fig. 6a), whereas it failed to affect USVs in VPA-exposed rats (Fig. 6a).
To block the activity of group II mGlu receptors, we used LY341495, a drug that preferentially antagonizes mGlu2 and mGlu3 receptors (reviewed by Schoepp et al. 1999). Systemic treatment with LY341495 (1 mg/kg, 1 h before the test) did not affect USVs in control rats and mitigated the reduced USV emission in VPA-exposed infant rats, although this effect was not statistically significant. Interestingly, after treatment with LY341495, there was no significant difference between control and VPA-treated rats on vocalization (Fig. 6b).
Discussion
Here, we found an increase of mGlu1, mGlu5, and mGlu2/3 receptor expressions in the synapses of infant rats prenatally exposed to VPA. These differences disappeared in adolescent and adult rats, suggesting that the upregulation of these receptors occurring in the early life is corrected or compensated over the course of postnatal development. Alterations in neuronal excitability, connectivity, and synaptic plasticity were found in VPA-exposed rats during infancy (Rinaldi et al. 2007; 2008; Walcott et al. 2011). It will be interesting to examine the causal relationship between these changes and the upregulation of mGlu1, mGlu5, and mGlu2/3 receptors.
mGlu1 and mGlu5 show structural similarities but have a different brain distribution and exhibit different functional roles (Hermans and Challiss 2001). A limited number of studies have investigated a possible involvement of mGlu1 in ASD. An increased expression and activity of mGlu1 receptors have been found in the striatum of Shank2 KO mice (Modi et al. 2018), and a correction of repetitive behavior (reduced marble burying) has been reported in the fragile X syndrome mouse model after administration of the mGlu1 negative allosteric modulator, JNJ16259685 (Thomas et al. 2012). Inhibition of mGlu1, as well as mGlu5, also reversed deficits in social interaction and marble burying caused by deficiency of the translation repressor eIF4E binding protein 2 (Aguilar-Valles et al. 2015). Previous studies carried out in VPA-exposed rats showed an upregulation of mGlu1 receptor mRNA in different brain regions (Schiavi et al. 2022) and an increase in mGlu1 receptor protein levels in the hilus of the dentate gyrus and in the CA1 alveus region of the hippocampus at P30 (Peralta et al. 2016), but not in the somatosensory cortex at P14 (Rinaldi et al. 2007). We found an increase in mGlu1α receptor protein levels in forebrain synaptosomes at P13, but not at P35 and P90. Taken together, these findings suggest that prenatal exposure to VPA induces age- and region-dependent changes in the expression of mGlu1 receptors and lay the groundwork for future studies on mGlu1 receptors in models of ASD.
Unlike mGlu1 receptor, the involvement of mGlu5 receptor in ASD has been extensively studied, and changes in mGlu5 receptor expression have been reported in ASD patients (Boer et al. 2008; Fatemi et al. 2011, 2018; Lohith et al. 2013; Brašić et al. 2021; Mody et al. 2021; Carey et al. 2022; Galineau et al. 2023) and in different animal models of autism (Giuffrida et al. 2005, Verpelli et al. 2011, D’Antoni et al. 2014; Pignatelli et al. 2014, Gogliotti et al. 2016; Lee et al. 2019; Carey et al. 2022; Matrisciano et al. 2022; Di Menna et al. 2023). Nevertheless, the expression of mGlu5 receptors has not been systematically and longitudinally studied in VPA-exposed rats. No changes in mGlu5 receptor expression were detected in the somatosensory cortex and the prefrontal cortex of 2-week-old offspring of VPA-treated dams (Rinaldi et al. 2007; Kim et al. 2016) and in the hippocampus of VPA-exposed rats at P30 (Peralta et al. 2016). In contrast, an increase in mGlu5 receptor expression was found in the prefrontal cortex of 4-week-old VPA-exposed rats (Kim et al. 2016) and in the retina of VPA-exposed mice at P30 (Guimarães-Souza et al. 2019). A recent [18F] FPEB positron emission tomography imaging study revealed an increased mGlu5 receptor density in the cortex, hippocampus, amygdala, and striatum and a reduced mGlu5 receptor density in the thalamus, mesencephalon, and cerebellum in P35 VPA-exposed rats (Galineau et al. 2023). Thus, the absence of changes that we detected at P35 or P90 in synaptosomes from forebrain does not exclude regional modifications of synaptic expression of mGlu5 receptors at later ages. The increased mGlu5 receptor expression found in synaptosomes of VPA-exposed rats at P13 is in line with the reported increase in cortical long-term microcircuit plasticity (Silva et al. 2009), a form of plasticity that involves mGlu5 receptors (Le Be and Markram 2006), in VPA-exposed rats at P12–P15.
An excitatory/inhibitory imbalance is a characteristic of ASD (Gao and Penzes 2015; Howell and Smith 2019) and has also been reported in VPA-exposed rats (Kim et al. 2014, 2016; Lenart et al. 2020). Furthermore, GABAergic neurotransmission is altered in VPA-exposed rats (Yang et al. 2021). It will be interesting to examine whether changes in GABAergic transmission are driven by mGlu1 or mGlu5 receptors expressed by interneurons.
It is known that the modulation of mGlu5 receptors improves the pathological phenotypes in several mouse models of autism (reviewed in D’Antoni et al. 2014; Aguilar-Valles et al. 2015; Gogliotti et al. 2016; Vicidomini et al. 2017). Pharmacological inhibition (or genetic deletion) of mGlu5 receptors rescues cognitive and social deficits in models of fragile X syndrome (FXS), the leading monogenic cause of ASD (Michalon et al. 2012, 2014; Gantois et al. 2013), and is also effective in other models of autism (Silverman et al. 2010, 2012; Tian et al. 2015; Aguilar-Valles et al. 2015; Matrisciano et al. 2022). Despite initial positive results and extensive preclinical research, clinical trials have failed to confirm beneficial effects in FXS patients (Jacquemont et al. 2011; Berry-Kravis et al. 2016; reviewed by Scharf et al. 2015; Emmitte 2017; Witkin et al. 2022). Further studies are needed to fully understand the lack of translation from preclinical studies to human trials in FXS patients (Berry-Kravis et al. 2018), from which the future development of drugs for other neurodevelopmental disorders could benefit.
Systemic treatment with the mGlu5 NAM, MPEP, in mice was found to reduce repetitive self-grooming and marble burying behaviors in the offspring of VPA-treated dams with no effect on anxiety-like behavior (Mehta et al. 2011) or social behavior (Kim et al. 2014). Because mGlu5 receptor protein levels were increased at P13, we examined the effect of mGlu5 receptor blockade on autism-like phenotype in VPA-exposed infant rats. We used MTEP because it is more potent, selective, and orally bioavailable than MPEP (Cosford et al. 2003). We observed that MTEP (1 mg/kg) caused a significant reduction of USVs in control mice; this finding is in line with data obtained by others and can be related to the anxiolytic-like effects of mGlu5 antagonists (Iijima and Chaki 2005; Hodgson et al 2008). In contrast, systemic treatment with MTEP failed to induce changes in USVs in VPA-exposed rats, suggesting that the upregulation of mGlu5 receptors is not causally related to this specific manifestation of autism-like behavior.
mGlu2 and mGlu3 receptors are coupled to Gi/o proteins and are mainly expressed on pre-synaptic terminals, where they negatively regulate glutamate and GABA release (reviewed by Nicoletti et al. 2011). However, mGlu3 receptors are also present postsynaptically, where they functionally interact with mGlu5 receptors. This interaction is involved in mechanisms of activity-dependent synaptic plasticity in the prefrontal cortex and hippocampus (Di Menna et al. 2018; Joffe et al. 2021; Dogra et al. 2021).
Group II mGlu receptors play a role in depression (for a review, see Chaki 2017), cognition, and neuropsychiatric disorders, such as schizophrenia (for reviews, see Harrison et al. 2008; Maksymetz et al. 2017), but have been scantly studied in neurodevelopmental disorders. A decreased expression of mGlu2 and mGlu3 receptors has been observed in a mouse model and in patients with Rett syndrome, whereas an increased expression of both mGlu2 and mGlu3 receptors has been reported in a mouse model of MECP2 duplication syndrome (Vermudez et al. 2022). Reduced mGlu2 receptor protein and mRNA levels were detected in the hippocampus of young mice (P48) subjected to 4 weeks postweaning social isolation and in the BTBR mice, an idiopathic model of ASD (Caruso et al. 2022). Reductions in mGlu2/3 receptor protein levels and mGlu2 receptor mRNA levels were found in the amygdala of the offspring of VPA-treated dams at P21 (Chen et al. 2014), whereas no changes in mGlu2/3 receptor protein levels were detected in VPA-treated mice at P30 (Wang et al. 2021). These results, combined with our findings, suggest that changes in group II mGlu receptor expression induced by prenatal exposure to VPA are age-dependent and occur in the early postnatal life.
Systemic treatment with the preferential mGlu2/3 receptor antagonist, LY341495, had a beneficial effect on the pathological phenotype in a mouse model of the FXS (Choi et al. 2011) and in a rodent model of the MECP2 duplication syndrome (Vermudez et al. 2022). Our evidence that low doses of LY341495 (1 mg/kg, 1 h before the test) enhanced USVs in VPA-exposed rats, but not in control rats, suggests that pharmacological blockade of mGlu2/3 receptors may correct some early behavioral abnormalities associated with ASD. Chen et al. reported that a chronic treatment with N-acetylcysteine improved social and anxiety behavior in VPA-exposed rats, possibly acting through the activation of mGlu2 receptors in the amygdala (Chen et al. 2014). Altogether, these data corroborate the view that both activation and inhibition of group II mGlu receptors may have a therapeutic potential, with different effects depending on age. Interestingly, TP0473292 (TS-161), a novel safe, well-tolerated, and orally bioavailable in humans orthosteric mGlu2/3 receptor antagonist prodrug, having antidepressant-like effects in animal models, is now ready for use in clinical studies for treatment of depression and potentially for other neuropsychiatric disorders (Watanabe et al. 2022; Inatani et al. 2023).
It has been reported that mGlu2/3 receptor antagonists modulate the activity of dopaminergic and serotonergic systems (for a review, see Chaki 2019), which are altered in VPA-exposed rats (Nakasato et al. 2008; Schiavi et al. 2019; and reviewed by Kuo and Liu 2022). On the other hand, mGlu3 activation stimulates the production/release of brain-derived neurotrophic factor (BDNF) (Suzuki et al. 2017), which is abnormal in the VPA model of ASD (Almeida et al. 2014; Fuentealba et al. 2019). Whether changes in monoaminergic neurotransmission and/or production of BDNF contribute to the “therapeutic” effect of mGlu2/3 receptor blockade in VPA-exposed rats remains to be determined.
In summary, our findings provide additional evidence that changes in mGlu receptor subtypes are associated with ASD and suggest that, at least in the VPA model, mGlu2 and/or mGlu3 receptors might be targeted by therapeutic intervention particularly in the early phases of postnatal development. This attractive hypothesis should be validated using mGlu2 or mGlu3 selective NAMS, or extending the study to the VPA model in mice, which allows to establish whether genetic deletion of one or both receptors affects the development of the autism-like phenotype induced by prenatal exposure to VPA. Furthermore, we cannot exclude that the upregulation of mGlu receptors during early development could cause behavioral and cognitive deficits associated with autism later in life. Further research should be performed to understand whether an early overexpression of these receptors at synapses can affect neuronal connectivity and influence the trajectory of the disease.
Change history
09 November 2023
A Correction to this paper has been published: https://doi.org/10.1007/s00213-023-06494-5
References
Abrahams BS, Geschwind DH (2008) Advances in autism genetics: on the threshold of a new neurobiology. Nat Rev Genet 9(5):341–355. https://doi.org/10.1038/nrg2346
Aguilar-Valles A, Matta-Camacho E, Khoutorsky A, Gkogkas C, Nader K, Lacaille JC, Sonenberg N (2015) Inhibition of group I metabotropic glutamate receptors reverses autistic-like phenotypes caused by deficiency of the translation repressor eIF4E binding protein 2. J Neurosci 35(31):11125–11132. https://doi.org/10.1523/JNEUROSCI.4615-14.2015
Almeida LE, Roby CD, Krueger BK (2014) Increased BDNF expression in fetal brain in the valproic acid model of autism. Mol Cell Neurosci 59:57–62. https://doi.org/10.1016/j.mcn.2014.01.007
Ango F, Prézeau L, Muller T, Tu JC, Xiao B, Worley PF, Pin JP, Bockaert J, Fagni L (2001) Agonist-independent activation of metabotropic glutamate receptors by the intracellular protein Homer. Nature 411(6840):962–965. https://doi.org/10.1038/35082096
Bear MF, Huber KM, Warren ST (2004) The mGluR theory of fragile X mental retardation. Trends Neurosci 27(7):370–377. https://doi.org/10.1016/j.tins.2004.04.009
Berry-Kravis E, Des Portes V, Hagerman R, Jacquemont S, Charles P, Visootsak J, Brinkman M, Rerat K, Koumaras B, Zhu L, Barth GM, Jaecklin T, Apostol G, von Raison F (2016) Mavoglurant in fragile X syndrome: results of two randomized, double-blind, placebo-controlled trials. Sci Transl Med 8(321):321ra5. https://doi.org/10.1126/scitranslmed.aab4109
Berry-Kravis EM, Lindemann L, Jønch AE, Apostol G, Bear MF, Carpenter RL, Crawley JN, Curie A, Des Portes V, Hossain F, Gasparini F, Gomez-Mancilla B, Hessl D, Loth E, Scharf SH, Wang PP, Von Raison F, Hagerman R, Spooren W, Jacquemont S (2018) Drug development for neurodevelopmental disorders: lessons learned from fragile X syndrome. Nat Rev Drug Discov 17(4):280–299. https://doi.org/10.1038/nrd.2017.221
Boer K, Troost D, Timmermans W, Gorter JA, Spliet WG, Nellist M, Jansen F, Aronica E (2008) Cellular localization of metabotropic glutamate receptors in cortical tubers and subependymal giant cell tumors of tuberous sclerosis complex. Neurosci 156(1):203–215. https://doi.org/10.1016/j.neuroscience.2008.06.073
Brašić JR, Nandi A, Russell DS, Jennings D, Barret O, Martin SD, Slifer K, Sedlak T, Seibyl JP, Wong DF, Budimirovic DB (2021) Cerebral expression of metabotropic glutamate receptor subtype 5 in idiopathic autism spectrum disorder and fragile X syndrome: A Pilot Study. Int J Mol Sci 22(6):2863. https://doi.org/10.3390/ijms22062863
Carey C, Singh N, Dunn JT, Sementa T, Mendez MA, Velthuis H, Pereira AC, Pretzsch CM, Horder J, Hader S, Lythgoe DJ, Rotaru DG, Gee A, Cash D, Veronese M, Murphy D, McAlonan G (2022) From bench to bedside: the mGluR5 system in people with and without autism spectrum disorder and animal model systems. Transl Psychiatry 12(1):395. https://doi.org/10.1038/s41398-022-02143-1
Caruso A, Ricceri L, Caruso A, Nicoletti F, Gaetano A, Scaccianoce S (2022) Postweaning social isolation and autism-like phenotype: a biochemical and behavioral comparative analysis. Behav Brain Res 428:113891. https://doi.org/10.1016/j.bbr.2022.113891
Chaki S (2017) mGlu2/3 receptor antagonists as novel antidepressants. Trends Pharmacol Sci 38(6):569–580. https://doi.org/10.1016/j.tips.2017.03.008
Chaki S (2019) mGlu2/3 receptor antagonists. Adv Pharmacol 86:97–120. https://doi.org/10.1016/bs.apha.2019.03.004
Chau DK, Choi AY, Yang W, Leung WN, Chan CW (2017) Downregulation of glutamatergic and GABAergic proteins in valproic acid associated social impairment during adolescence in mice. Behav Brain Res 316:255–260. https://doi.org/10.1016/j.bbr.2016.09.003
Chen YW, Lin HC, Ng MC, Hsiao YH, Wang CC, Gean PW, Chen PS (2014) Activation of mGluR2/3 underlies the effects of N-acetylcystein on amygdala-associated autism-like phenotypes in a valproate-induced rat model of autism. Front Behav Neurosci 8:219. https://doi.org/10.3389/fnbeh.2014.00219
Choi CH, Schoenfeld BP, Bell AJ, Hinchey P, Kollaros M, Gertner MJ, Woo NH, Tranfaglia MR, Bear MF, Zukin RS, McDonald TV, Jongens TA, McBride SM (2011) Pharmacological reversal of synaptic plasticity deficits in the mouse model of fragile X syndrome by group II mGluR antagonist or lithium treatment. Brain Res 1380:106–119. https://doi.org/10.1016/j.brainres.2010.11.032
Christensen J, Grønborg TK, Sørensen MJ, Schendel D, Parner ET, Pedersen LH, Vestergaard M (2013) Prenatal valproate exposure and risk of autism spectrum disorders and childhood autism. JAMA 309(16):1696–1703. https://doi.org/10.1001/jama.2013.2270
Cosford ND, Tehrani L, Roppe J, Schweiger E, Smith ND, Anderson J, Bristow L, Brodkin J, Jiang X, McDonald I, Rao S, Washburn M, Varney MA (2003) 3-[(2-Methyl-1,3-thiazol-4-yl)ethynyl]-pyridine: a potent and highly selective metabotropic glutamate subtype 5 receptor antagonist with anxiolytic activity. J Med Chem 46(2):204–206. https://doi.org/10.1021/jm025570j
D’Antoni S, Berretta A, Bonaccorso CM, Bruno V, Aronica E, Nicoletti F, Catania MV (2008) Metabotropic glutamate receptors in glial cells. Neurochem Res 33(12):2436–2443. https://doi.org/10.1007/s11064-008-9694-9
D'Antoni S, Spatuzza M, Bonaccorso CM, Musumeci SA, Ciranna L, Nicoletti, Huber KM, Catania MV (2014) Dysregulation of group-I metabotropic glutamate (mGlu) receptor mediated signalling in disorders associated with Intellectual Disability and Autism. Neurosci Biobehav Rev 46 Pt 2(Pt 2): 228–41. https://doi.org/10.1016/j.neubiorev.2014.02.003.
Deckmann I, Santos-Terra J, Fontes-Dutra M, Körbes-Rockenbach M, Bauer-Negrini G, Schwingel GB, Riesgo R, Bambini-Junior V, Gottfried C (2021) Resveratrol prevents brainedema, blood-brain barrier permeability, and altered aquaporin profile in autism animal model. Int J Dev Neurosci 81(7):579–604. https://doi.org/10.1002/jdn.10137
Di Menna L, Joffe ME, Iacovelli L, Orlando R, Lindsley CW, Mairesse J, Gressèns P, Cannella M, Caraci F, Copani A, Bruno V, Battaglia G, Conn PJ, Nicoletti F (2018) Functional partnership between mGlu3 and mGlu5 metabotropic glutamate receptors in the central nervous system. Neuropharmacol 128:301–313. https://doi.org/10.1016/j.neuropharm.2017.10.026
Di Menna L, Orlando R, D’Errico G, Ginerete RP, Machaczka A, Bonaccorso CM, Arena A, Spatuzza M, Celli R, Alborghetti M, Ciocca E, Zuena AR, Scioli MR, Bruno V, Battaglia G, Nicoletti F, Catania MV (2023) Blunted type-5 metabotropic glutamate receptor-mediated polyphosphoinositide hydrolysis in two mouse models of monogenic autism. Neuropharmacol 238:109642. https://doi.org/10.1016/j.neuropharm.2023.109642
Dogra S, Stansley BJ, Xiang Z, Qian W, Gogliotti RG, Nicoletti F, Lindsley CW, Niswender CM, Joffe ME, Conn PJ (2021) Activating mGlu3 metabotropic glutamate receptors rescues schizophrenia-like cognitive deficits through metaplastic adaptations within the hippocampus. Biol Psychiatry 90(6):385–398. https://doi.org/10.1016/j.biopsych.2021.02.970
Ebrahimi-Fakhari D, Sahin M (2015) Autism and the synapse: emerging mechanisms and mechanism-based therapies. Curr Opin Neurol 28(2):91–102. https://doi.org/10.1097/WCO.0000000000000186
Emmitte KA (2017) mGlu5 negative allosteric modulators: a patent review (2013–2016). Expert Opin Ther Pat 27(6):691–706. https://doi.org/10.1080/13543776.2017.1280466
Fatemi SH, Folsom TD, Kneeland RE, Liesch SB (2011) Metabotropic glutamate receptor 5 upregulation in children with autism is associated with underexpression of both Fragile X mental retardation protein and GABAA receptor beta 3 in adults with autism. Anat Rec (hoboken) 294:1635–1645. https://doi.org/10.1002/ar.21299
Fatemi SH, Wong DF, Brašić JR, Kuwabara H, Mathur A, Folsom TD, Jacob S, Realmuto GM, Pardo JV, Lee S (2018) Metabotropic glutamate receptor 5 tracer [18F]-FPEB displays increased binding potential in postcentral gyrus and cerebellum of male individuals with autism: a pilot PET study. Cerebellum Ataxias 5:3. https://doi.org/10.1186/s40673-018-0082-1
Fuentealba CR, Fiedler JL, Peralta FA, Avalos AM, Aguayo FI, Morgado-Gallardo KP, Aliaga EE (2019) Region-specific reduction of BDNF protein and transcripts in the hippocampus of juvenile rats prenatally treated with sodium valproate. Front Mol Neurosci 12:261. https://doi.org/10.3389/fnmol.2019.00261
Galineau L, Arlicot N, Dupont AC, Briend F, Houy-Durand E, Tauber C, Gomot M, Gissot V, Barantin L, Lefevre A, Vercouillie J, Roussel C, Roux S, Nadal L, Mavel S, Laumonnier F, Belzung C, Chalon S, Emond P, Santiago-Ribeiro MJ, Bonnet-Brilhault F (2023) Glutamatergic synapse in autism: a complex story for a complex disorder. Mol Psychiatry 28(2):801–809. https://doi.org/10.1038/s41380-022-01860-9
Gantois I, Pop AS, de Esch CE, Buijsen RA, Pooters T, Gomez-Mancilla B, Gasparini F, Oostra BA, D’Hooge R, Willemsen R (2013) Chronic administration of AFQ056/mavoglurant restores social behaviour in Fmr1 knockout mice. Behav Brain Res 239:72–79. https://doi.org/10.1016/j.bbr.2012.10.059
Gao R, Penzes P (2015) Common mechanisms of excitatory and inhibitory imbalance in schizophrenia and autism spectrum disorders. Curr Mol Med 15(2):146–167. https://doi.org/10.2174/1566524015666150303003028
Giuffrida R, Musumeci S, D’Antoni S, Bonaccorso CM, Giuffrida-Stella AM, Oostra BA, Catania MV (2005) A reduced number of metabotropic glutamate subtype 5 receptors are associated with constitutive Homer proteins in a mouse model of fragile X syndrome. J Neurosci 25(39):8908–8916. https://doi.org/10.2174/1566524015666150303003028
Gogliotti RG, Senter RK, Rook JM, Ghoshal A, Zamorano R, Malosh C, Stauffer SR, Bridges TM, Bartolome JM, Daniels JS, Jones CK, Lindsley CW, Conn PJ, Niswender CM (2016) mGlu5 positive allosteric modulation normalizes synaptic plasticity defects and motor phenotypes in a mouse model of Rett syndrome. Hum Mol Genet 25(10):1990–2004. https://doi.org/10.1093/hmg/ddw074
Guimarães-Souza EM, Joselevitch C, Britto LRG (2019) Chiavegatto S (2019) Retinal alterations in a pre-clinical model ofan autism spectrum disorder. Molecular Autism 10:19. https://doi.org/10.1186/s13229-019-0270-8.eCollection
Harrison PJ, Lyon L, Sartorius LJ, Burnet PWJ, Lane TA (2008) The group II metabotropic glutamate receptor 3 (mGluR3, mGlu3, GRM3): expression, function and involvement in schizophrenia. J Psychopharmacol 22:308–322. https://doi.org/10.1177/0269881108089818
Hermans E, Challiss RA (2001) Structural, signalling and regulatory properties of the group I metabotropic glutamate receptors: prototypic family C G-protein-coupled receptors. Biochem J 359(Pt 3):465–484. https://doi.org/10.1042/0264-6021:3590465
Hodgson RA, Guthrie DH, Varty GB (2008) Duration of ultrasonic vocalizations in the isolated rat pup as a behavioral measure: sensitivity to anxiolytic and antidepressant drugs. Pharmacol Biochem Behav 88(3):341–348. https://doi.org/10.1016/j.pbb.2007.09.005
Howell BW, Smith KM (2019) Synaptic structural protein dysfunction leads to altered excitation inhibition ratios in models of autism spectrum disorder. Pharmacol Res 139:207–214. https://doi.org/10.1016/j.phrs.2018.11.019
Iijima M, Chaki S (2005) Separation-induced ultrasonic vocalization in rat pups: further pharmacological characterization. Pharmacol Biochem Behav 82(4):652–657. https://doi.org/10.1016/j.pbb.2005.11.005
Inatani S, Ochi M, Kinoshita K, Yamaguchi JI, Endo H (2023) Preclinical metabolism and disposition of TP0473292, a novel oral prodrug of the potent metabotropic glutamate 2/3 receptor antagonist TP0178894 for the treatment of depression. Drug Metab Dispos 51(5):572–582. https://doi.org/10.1124/dmd.122.001116
Jacquemont S, Curie A, Des Portes V, Torrioli MG, Berry-Kravis E, Hagerman RJ, Ramos FJ, Cornish K, He Y, Paulding C, Neri G, Chen F, Hadjikhani N, Martinet D, Meyer J, Beckmann JS, Delange K, Brun A, Bussy G, Gasparini F, Hilse T, Floesser A, Branson J, Bilbe G, Johns D, Gomez-Mancilla B (2011) Epigenetic modification of the FMR1 gene in fragile X syndrome is associated with differential response to the mGluR5 antagonist AFQ056. Sci Transl Med 3(64):64ra1. https://doi.org/10.1126/scitranslmed.3001708
Joffe ME, Santiago CI, Vermudez SAD, Fisher NM, Dogra S, Niswender CM, Jeffrey Conn P (2021) Frontal cortex genetic ablation of metabotropic glutamate receptor subtype 3 (mGlu3) impairs postsynaptic plasticity and modulates affective behaviors. Neuropsychopharmacol 46(12):2148–2157. https://doi.org/10.1038/s41386-021-01041-2
Kammermeier PJ, Xiao B, Tu JC, Worley PF, Ikeda SR (2000) Homer proteins regulate coupling of group I metabotropic glutamate receptors to N-type calcium and Mtype potassium channel. J Neurosci 20(19):7238–7245. https://doi.org/10.1523/JNEUROSCI.20-19-07238.2000
Kim KC, Lee D-K, Go HS, Kim P, Choi CS, Kim J-W, Jeon SJ, Song M-R, Shin CY (2014) Pax6-dependent cortical glutamatergic neuronal differentiation regulates autism-like behavior in prenatally valproic acid-exposed rat offspring. Mol Neurobiol 49:512–528. https://doi.org/10.1007/s12035-013-8535-2
Kim KC, Choi CS, Kim JW, Han SH, Cheong JH, Ryu JH, Shin CY (2016) MeCP2 modulates sex differences in the postsynaptic development of the valproate animal model of autism. Mol Neurobiol 53(1):40–56. https://doi.org/10.1007/s12035-014-8987-z
Kim JW, Seung H, Kim KC, Gonzales ELT, Oh HA, Yang SM, Ko MJ, Han SH, Banerjee S, Shin CY (2017) Agmatine rescues autistic behaviors in the valproic acid-induced animal model of autism. Neuropharmacol 113(Pt A):71–81. https://doi.org/10.1016/j.neuropharm.2016.09.014
Kuo HY, Liu FC (2022) Pathophysiological studies of monoaminergic neurotransmission systems in valproic acid-induced model of autism spectrum disorder. Biomedicines 10(3):560. https://doi.org/10.3390/biomedicines10030560
Le Be J-V, Markram H (2006) Spontaneous and evoked synaptic rewiring in the neonatal neocortex. Proc Natl Acad Sci USA 103:13214–13219. https://doi.org/10.1073/pnas.0604691103
Lee K, Vyas Y, Garner CC, Montgomery JM (2019) Autism-associated Shank3 mutations alter mGluR expression and mGluR-dependent but not NMDA receptor-dependent long-term depression. Synapse 73(8):e22097. https://doi.org/10.1002/syn.22097
Lenart J, Augustyniakm J, Lazarewicz JW, Zieminska E (2020) Altered expression of glutamatergic and GABAergic genes in the valproic acid-induced rat model of autism: a screening test. Toxicology 440:152500. https://doi.org/10.1016/j.tox.2020.152500
Lin HC, Gean PW, Wang CC, Chan YH, Chen PS (2013) The amygdala excitatory/inhibitory balance in a valproate-induced rat autism model. PLoS One 8(1):e55248. https://doi.org/10.1371/journal.pone.0055248
Lohith TG, Osterweil EK, Fujita M, Jenko KJ, Bear MF, Innis RB (2013) Is metabotropic glutamate receptor 5 upregulated in prefrontal cortex in fragile X syndrome? Mol Autism 4:1–1. https://doi.org/10.1186/2040-2392-4-15
Lord C, Brugha TS, Charman T, Cusack J, Dumas G, Frazier T, Jones EJH, Jones RM, Pickles A, State MW, Taylor JL, Veenstra-VanderWeele J (2020) Autism spectrum disorder. Nat Rev Dis Primers 6(1):5. https://doi.org/10.1016/S0140-6736(18)31129-2
Löscher W (2002) Basic pharmacology of valproate. CNS Drugs 16(10):669–694. https://doi.org/10.2165/00023210-200216100-00003
Maksymetz J, Moran SP, Conn PJ (2017) Targeting metabotropic glutamate receptors for novel treatments of schizophrenia. Mol Brain 10:15. https://doi.org/10.1186/s13041-017-0293-z
Martin HG, Manzoni OJ (2014) Late onset deficits in synaptic plasticity in the valproic acid rat model of autism. Front Cell Neurosci 8:23. https://doi.org/10.3389/fncel.2014.00023
Matrisciano F, Locci V, Dong E, Nicoletti F, Guidotti A, Grayson DR (2022) Altered expression and in vivo activity of mGlu5 Variant a receptors in the striatum of BTBR mice: novel insights into the pathophysiology of adult idiopathic forms of autism spectrum disorders. Curr Neuropharmacol 20(12):2354–2368. https://doi.org/10.2174/1567202619999220209112609
Mehta MV, Gandal MJ, Siegel SJ (2011) mGluR5-antagonist mediated reversal of elevated stereotyped, repetitive behaviors in the VPA model of autism. PLoS One 6(10):e26077. https://doi.org/10.1371/journal.pone.0026077
Melancia F, Schiavi S, Servadio M, Cartocci V, Campolongo P, Palmery M, Pallottini V, Trezza V (2018) Sex-specific autistic endophenotypes induced by prenatal exposure to valproic acid involve anandamide signalling. Br J Pharmacol 175(18):3699–3712. https://doi.org/10.1111/bph.14435
Michalon A, Sidorov M, Ballard TM, Ozmen L, Spooren W, Wettstein JG, Jaeschke G, Bear MF, Lindemann L (2012) Chronic pharmacological mGlu5 inhibition corrects fragile X in adult mice. Neuron 74(1):49–56. https://doi.org/10.1016/j.neuron.2012.03.009
Michalon A, Bruns A, Risterucci C, Honer M, Ballard TM, Ozmen L, Jaeschke G, Wettstein JG, von Kienlin M, Künnecke B, Lindemann L (2014) Chronic metabotropic glutamate receptor 5 inhibition corrects local alterations of brain activity and improves cognitive performance in fragile X mice. Biol Psychiatry 75(3):189–197. https://doi.org/10.1016/j.biopsych.2013.05.038
Modi ME, Brooks JM, Guilmette ER, Beyna M, Graf R, Reim D, Schmeisser MJ, Boeckers TM, O’Donnell P (2018) Buhl DL (2018) Hyperactivity and hypermotivation associated with increased striatal mGluR1 signaling in a Shank2 rat model of autism. Front Mol Neurosci 11:107. https://doi.org/10.3389/fnmol.2018.00107.eCollection
Mody M, Petibon Y, Han P, Kuruppu D, Ma C, Yokell D, Neelamegam R, Normandin MD, Fakhri GE, Brownell AL (2021) In vivo imaging of mGlu5 receptor expression in humans with fragile X syndrome towards development of a potential biomarker. Sci Rep 11(1):15897. https://doi.org/10.1038/s41598-021-94967-y
Nakasato A, Nakatani Y, Seki Y, Tsujino N, Umino M, Arita H (2008) Swim stress exaggerates the hyperactive mesocortical dopamine system in a rodent model of autism. Brain Res 1193:128–135. https://doi.org/10.1016/j.brainres.2007.11.043
Nicoletti F, Bockaert J, Collingridge GL, Conn PJ, Ferraguti F, Schoepp DD, Wroblewski JT, Pin JP (2011) Metabotropic glutamate receptors: from the workbench to the bedside. Neuropharmacol 60(7–8):1017–1041. https://doi.org/10.1016/j.neuropharm.2010.10.022
Nicolini C, Fahnestock M (2018) The valproic acid-induced rodent model of autism. Exp Neurol 299(Pt A):217–227. https://doi.org/10.1016/j.expneurol.2017.04.017
Nisar S, Bhat AA, Masoodi T, Hashem S, Akhtar S, Ali TA, Amjad S, Chawla S, Bagga P, Frenneaux MP, Reddy R, Fakhro K, Haris M (2022) Genetics of glutamate and its receptors in autism spectrum disorder. Mol Psychiatry 27(5):2380–2392. https://doi.org/10.1038/s41380-022-01506-w
Park S, Park JM, Kim S, Kim JA, Shepherd JD, Smith-Hicks CL, Chowdhury S, Kaufmann W, Kuhl D, Ryazanov AG, Huganir RL, Linden DJ, Worley PF (2008) Elongation factor 2 and fragile X mental retardation protein control the dynamic translation of Arc/Arg3.1 essential for mGluR-LTD. Neuron 59:70–83. https://doi.org/10.1016/j.neuron.2008.05.023
Peralta F, Fuentealba C, Fiedler J, Aliaga E (2016) Prenatal valproate treatment produces autistic-like behavior and increases metabotropic glutamate receptor 1A-immunoreactivity in the hippocampus of juvenile rats. Mol Med Rep 14(3):2807–2814. https://doi.org/10.3892/mmr.2016.5529
Petrelli F, Bezzi P (2018) mGlu5-mediated signalling in developing astrocyte and the pathogenesis of autism spectrum disorders. Curr Opin Neurobiol 48:139–145. https://doi.org/10.1016/j.conb.2017.12.014
Pignatelli M, Piccinin S, Molinaro G, Di Menna L, Riozzi B, Cannella M, Motolese M, Vetere G, Catania MV, Battaglia G, Nicoletti F, Nisticò R, Bruno V (2014) Changes in mGlu5 receptor-dependent synaptic plasticity and coupling to Homer proteins in the hippocampus of Ube3A hemizygous mice modeling angelman syndrome. J Neurosci 34(13):4558–4566. https://doi.org/10.1523/JNEUROSCI.1846-13.2014
Reiner A, Levitz J (2018) Glutamatergic signaling in the central nervous system: ionotropic and metabotropic receptors in concert. Neuron 98(6):1080–1098. https://doi.org/10.1016/j.neuron.2018.05.018
Rinaldi T, Kulangara K, Antoniello K, Markram H (2007) Elevated NMDA receptor levels and enhanced postsynaptic long-term potentiation induced by prenatal exposure to valproic acid. Proc Natl Acad Sci 104:13501–13506. https://doi.org/10.1073/pnas.0704391104
Rinaldi T, Silberberg G, Markram H (2008) Hyperconnectivity of local neocortical microcircuitry induced by prenatal exposure to valproic acid. Cereb Cortex 18(4):763–770. https://doi.org/10.1093/cercor/bhm117
Rubenstein JL, Merzenich MM (2003) Model of autism: increased ratio of excitation/inhibition in key neural systems. Genes Brain Behav 2:255–267. https://doi.org/10.1034/j.1601-183x.2003.00037.x
Scharf SH, Jaeschke G, Wettstein JG, Lindemann L (2015) Metabotropic glutamate receptor 5 as drug target for Fragile X syndrome. Curr Opin Pharmacol 20:124–134. https://doi.org/10.1016/j.coph.2014.11.004
Schiavi S, Iezzi D, Manduca A, Leone S, Melancia F, Carbone C, Petrella M, Mannaioni G, Masi A (2019) Trezza V (2019) Reward-related behavioral, neurochemical and electrophysiological changes in a rat model of autism based on prenatal exposure to valproic acid. Front Cell Neurosci 13:479. https://doi.org/10.3389/fncel.2019.00479.eCollection
Schiavi S, La Rosa P, Petrillo S, Carbone E, D’Amico J, Piemonte F, Trezza V (2022) N-Acetylcysteine mitigates social dysfunction in a rat model of autism normalizing glutathione imbalance and the altered expression of genes related to synaptic function in specific brain areas. Front Psychiatry 13:851679
Schoepp DD, Jane DE, Monn JA (1999) Pharmacological agents acting at subtypes of metabotropic glutamate receptors. Neuropharmacol 38(10):1431–1476. https://doi.org/10.1016/s0028-3908(99)00092-1
Sealey LA, Hughes BW, Sriskanda AN, Guest JR, Gibson AD, Johnson-Williams L, Pace DG, Bagasra O (2016) Environmental factors in the development of autism spectrum disorders. Environ Int 88:288–298. https://doi.org/10.1016/j.envint.2015.12.021
Servadio M, Vanderschuren LJ, Trezza V (2015) Modeling autism-relevant behavioral phenotypes in rats and mice: Do ‘autistic’ rodents exist? Behav Pharmacol 26(6):522–540. https://doi.org/10.1097/FBP.0000000000000163
Servadio M, Melancia F, Manduca A, di Masi A, Schiavi S, Cartocci V, Pallottini V, Campolongo P, Ascenzi P, Trezza V (2016) Targeting anandamide metabolism rescues core and associated autistic-like symptoms in rats prenatally exposed to valproic acid. Transl Psychiatry 6:e902. https://doi.org/10.1038/tp.2016.182
Silva GT, Le Bé JV, Riachi I, Rinaldi T, Markram K (2009) Markram H (2009) Enhanced long-term microcircuit plasticity in the valproic acid animal model of autism. Front Synaptic Neurosci 1:1. https://doi.org/10.3389/neuro.19.001.2009.eCollection
Silverman JL, Tolu SS, Barkan CL, Crawley JN (2010) Repetitive self-grooming behavior in the BTBR mouse model of autism is blocked by the mGluR5 antagonist MPEP. Neuropsychopharmacology 35(4):976–989. https://doi.org/10.1038/npp.2009.201
Silverman JL, Smith DG, Rizzo SJ, Karras MN, Turner SM, Tolu SS, Bryce DK, Smith DL, Fonseca K, Ring RH, Crawley JN (2012) Negative allosteric modulation of the mGluR5 receptor reduces repetitive behaviors and rescues social deficits in mouse models of autism. Sci Transl Med 4(131):131ra51. https://doi.org/10.1126/scitranslmed.3003501
Spampinato SF, Copani A, Nicoletti F, Sortino MA, Caraci F (2018) Metabotropic glutamate receptors in glial cells: a new potential target for neuroprotection? Front Mol Neurosci 11:414. https://doi.org/10.3389/fnmol.2018.00414
Suzuki S, Koshimizu H, Adachi N, Matsuoka H, Fushimi S, Ono J, Ohta KI, Miki T (2017) Functional interaction between BDNF and mGluR II in vitro: BDNF down-regulated mGluR II gene expression and an mGluR II agonist enhanced BDNF-induced BDNF gene expression in rat cerebral cortical neurons. Peptides 89:42–49. https://doi.org/10.1016/j.peptides.2017.01.007
Tartaglione AM, Schiavi S, Calamandrei G, Trezza V (2019) Prenatal valproate in rodents as a tool to understand the neural underpinnings of social dysfunctions in autism spectrum disorder. Neuropharmacol 159:107477. https://doi.org/10.1016/j.neuropharm.2018.12.024
Thomas AM, Bui N, Perkins JR, Yuva-Paylor LA, Paylor R (2012) Group I metabotropic glutamate receptor antagonists alter select behaviors in a mouse model for fragile X syndrome. Psychopharmacol 219(1):47–58. https://doi.org/10.1007/s00213-011-2375-4
Tian D, Stoppel LJ, Heynen AJ, Lindemann L, Jaeschke G, Mills AA, Bear MF (2015) Contribution of mGluR5 to pathophysiology in a mouse model of human chromosome 16p11.2 microdeletion. Nat Neurosci 18(2):182–4. https://doi.org/10.1038/nn.3911
Traynelis SF, Wollmuth LP, McBain CJ, Menniti FS, Vance KM, Ogden KK, Hansen KB, Yuan H, Myers SJ, Dingledine R (2010) Glutamate receptor ion channels: structure, regulation, and function. Pharmacol Rev 62(3):405–496. https://doi.org/10.1124/pr.109.002451
Tyzio R, Nardou R, Ferrari DC, Tsintsadze T, Shahrokhi A, Eftekhari S, Khalilov I, Tsintsadze V, Brouchoud C, Chazal G, Lemonnier E, Lozovaya N, Burnashev N, Ben-Ari Y (2014) Oxytocin-mediated GABA inhibition during delivery attenuates autism pathogenesis in rodent offspring. Science 343:675–679. https://doi.org/10.1126/science.1247190
Vermudez SAD, Buch A, Weiss K, Gogliotti RG, Niswender CM (2022) Exploration of group II metabotropic glutamate receptor modulation in mouse models of Rett syndrome andMECP2 Duplication syndrome. Neuropharmacol 209:109022. https://doi.org/10.1016/j.neuropharm.2022.109022
Verpelli C, Dvoretskova E, Vicidomini C, Rossi F, Chiappalone M, Schoen M, Di Stefano B, Mantegazza R, Broccoli V, Böckers TM, Dityatev A, Sala C (2011) Importance of Shank3 protein in regulating metabotropic glutamate receptor 5 (mGluR5) expression and signaling at synapses. J Biol Chem 286(40):34839–34850
Vicidomini C, Ponzoni L, Lim D, Schmeisser MJ, Reim D, Morello N, Orellana D, Tozzi A, Durante V, Scalmani P, Mantegazza M, Genazzani AA, Giustetto M, Sala M, Calabresi P, Boeckers TM, Sala C, Verpelli C (2017) Pharmacological enhancement of mGlu5 receptors rescues behavioral deficits in SHANK3 knock-out mice. Mol Psychiatry 22(5):689–702. https://doi.org/10.1038/mp.2016.30
Walcott EC, Higgins EA, Desai NS (2011) Synaptic and intrinsic balancing during postnatal development in rat pups exposed to valproic acid in utero. J Neurosci 31:13097–13109. https://doi.org/10.1523/JNEUROSCI.1341-11.2011
Wang H, Westin L, Nong Y, Birnbaum S, Bendor J, Brismar H, Nestler E, Aperia A, Flajolet M, Greengard P (2009) Norbin is an endogenous regulator of metabotropic glutamate receptor 5 signaling. Science 326(5959):1554–1557. https://doi.org/10.1126/science.1178496
Wang X, Gao C, Zhang Y, Hu S, Qiao Y, Zhao Z, Gou L, Song J (2021) Wang Q (2021) Overexpression of mGluR7 in the prefrontal cortex attenuates autistic behaviors in mice. Frot Cell Neurosci 15:689611. https://doi.org/10.3389/fncel.2021.689611.eCollection
Watanabe M, Marcy B, Hiroki A, Watase H, Kinoshita K, Iijima M, Marumo T, Zarate CA, Chaki S (2022) Evaluation of the safety, tolerability, and pharmacokinetic profiles of TP0473292 (TS-161), a prodrug of a novel orthosteric mGlu2/3 receptor antagonist TP0178894, in healthy subjects and its antidepressant-like effects in rodents. Int J Neuropsychopharmacol 25(2):106–117. https://doi.org/10.1093/ijnp/pyab062
Witkin JM, Pandey KP, Smith JL (2022) Clinical investigations of compounds targeting metabotropic glutamate receptors. Pharmacol Biochem Behav 219:173446. https://doi.org/10.1016/j.pbb.2022.173446
Yang JQ, Yang C-H, Yin B-Q (2021) Combined the GABA-A and GABA-B receptor agonists attenuates autistic behaviors in a prenatal valproic acid-induced mouse model of autism. Behav Brain Res 403:113094. https://doi.org/10.1016/j.bbr.2020.113094
Zoghbi HY, Bear MF (2012) Synaptic dysfunction in neurodevelopmental disorders associated with autism and intellectual disabilities. Cold Spring Harb Perspect Biol 4(3): a009886. https://doi.org/10.1101/cshperspect.a009886.
Funding
Open access funding provided by Consiglio Nazionale Delle Ricerche (CNR) within the CRUI-CARE Agreement. Funding for this study was provided by the Institute for Biomedical Research and Innovation, National Research Council (IRIB-CNR), Catania, Italy, and by the Department of Science, Section of Biomedical Sciences and Technologies, University “Roma Tre,” Rome, Italy. IRIB-CNR and University “Roma Tre” had no further role in the study design; in the collection, analysis, and interpretation of the data; in the writing of the report; and in the decision to submit the paper for publication.
Author information
Authors and Affiliations
Corresponding author
Ethics declarations
Conflict of interest
The authors declare no competing interests.
Additional information
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
The original version of this article was revised: This article was originally published with an incorrectly reported the codes of three antibodies.
Supplementary Information
Below is the link to the electronic supplementary material.
Rights and permissions
Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.
About this article
Cite this article
D’Antoni, S., Schiavi, S., Buzzelli, V. et al. Group I and group II metabotropic glutamate receptors are upregulated in the synapses of infant rats prenatally exposed to valproic acid. Psychopharmacology 240, 2617–2629 (2023). https://doi.org/10.1007/s00213-023-06457-w
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00213-023-06457-w