Abstract
Rationale
The midbrain raphe regions have long been implicated in affective processes and disorders. There is increasing evidence to suggest that the median (MR) and dorsal raphe nuclei (DR) tonically inhibit reward-related processes.
Objectives
Stimulation of GABAB receptors in the midbrain raphe nuclei is known to inhibit local neurons, especially serotonergic neurons. We sought to determine if injections of the GABAB receptor agonist baclofen into the MR or DR are rewarding, using intracranial self-administration and conditioned place preference.
Results
Rats quickly learned to lever press for infusions of baclofen (0.1–2.5 mM) into the MR, but not the ventral tegmental area or central linear nucleus. Rats increased lever pressing associated with intra-DR baclofen infusions, but not readily. Baclofen self-administration into the MR or DR was attenuated by coadministration of the GABAB receptor antagonist SCH 50911 (1 mM) or systemic pretreatment with the dopamine receptor antagonist SCH 23390 (0.025 mg/kg, i.p.). In addition, intra-DR and intra-MR injections of baclofen induced conditioned place preference; injection into DR was more effective.
Conclusions
Baclofen injections into the midbrain raphe nuclei are rewarding. Baclofen was more readily self-administered into the MR than into the DR, while baclofen injections into the DR more readily induced conditioned place preference than those into the MR. These sites may be differentially involved in aspects of reward. These findings suggest that MR or DR neurons containing GABAB receptors are involved in tonic inhibitory control over reward processes.
Similar content being viewed by others
References
Abellán MT, Adell A, Honrubia MA, Mengod G, Artigas F (2000a) GABAB-RI receptors in serotonergic neurons: effects of baclofen on 5-HT output in rat brain. Neuroreport 11:941–945
Abellán MT, Jolas T, Aghajanian GK, Artigas F (2000b) Dual control of dorsal raphe serotonergic neurons by GABA(B) receptors. Electrophysiological and microdialysis studies. Synapse 36:21–34
Behzadi G, Kalen P, Parvopassu F, Wiklund L (1990) Afferents to the median raphe nucleus of the rat: retrograde cholera toxin and wheat germ conjugated horseradish peroxidase tracing, and selective D-[3H]aspartate labelling of possible excitatory amino acid inputs. Neuroscience 37:77–100
Blier P, de Montigny C (1994) Current advances and trends in the treatment of depression. Trends Pharmacol Sci 15:220–226
Coccaro EF, Siever LJ, Klar HM, Maurer G, Cochrane K, Cooper TB, Mohs RC, Davis KL (1989) Serotonergic studies in patients with affective and personality disorders: correlates with suicidal and impulsive aggressive behavior. Arch Gen Psychiatry 46:587–599
Colmers WF, Williams JT (1988) Pertussis toxin pretreatment discriminates between pre- and postsynaptic actions of baclofen in rat dorsal raphe nucleus in vitro. Neurosci Lett 93:300–306
Cools R, Roberts AC, Robbins TW (2008) Serotoninergic regulation of emotional and behavioural control processes. Trends Cogn Sci 12:31–40
Cousins MS, Roberts DCS, Hd W (2002) GABAB receptor agonists for the treatment of drug addiction: a review of recent findings. Drug Alcohol Depend 65:209–220
Emrich HM, von Zerssen D, Kissling W, Mller HJ, Windorfer A (1980) Effect of sodium valproate on mania. The GABA-hypothesis of affective disorders. Arch Psychiatr Nervenkr 229:1–16
Fink H, Morgenstern R (1986) Behavioral function of GABA in the median raphe nucleus. Biomed Biochim Acta 45:531–538
Fletcher PJ, Ming Z-H, Higgins GA (1993) Conditioned place preference induced by microinjection of 8-OH-DPAT into the dorsal or median raphe nucleus. Psychopharmacology 113:31–36
Fletcher PJ, Tampakeras M, Yeomans JS (1995) Median raphe injections of 8-OH-DPAT lower frequency thresholds for lateral hypothalamic self-stimulation. Pharmacol Biochem Behav 52:65–71
Geisler S, Zahm DS (2005) Afferents of the ventral tegmental area in the rat-anatomical substratum for integrative functions. J Comp Neurol 490:270–294
Heilig M, Egli M (2006) Pharmacological treatment of alcohol dependence: target symptoms and target mechanisms. Pharmacol Ther 111:855–876
Ikemoto S, Sharpe LG (2001) A head-attachable device for injecting nanoliter volumes of drug solutions into brain sites of freely moving rats. J Neurosci Methods 110:135–140
Ikemoto S, Wise RA (2002) Rewarding effects of the cholinergic agents carbachol and neostigmine in the posterior ventral tegmental area. J Neurosci 22:9895–9904
Ikemoto S, Murphy JM, McBride WJ (1998) Regional differences within the rat ventral tegmental area for muscimol self-infusions. Pharmacol Biochem Behav 61:87–92
Innis RB, Aghajanian GK (1987) Pertussis toxin blocks 5-HT1A and GABAB receptor-mediated inhibition of serotonergic neurons. Eur J Pharmacol 143:195–204
Judge SJ, Ingram CD, Gartside SE (2004) GABA receptor modulation of 5-HT neuronal firing: characterization and effect of moderate in vivo variations in glucocorticoid levels. Neurochem Int 45:1057–1065
Kliteneck MA, Wirtshafter D (1988) Comparative studies of the ingestive behaviors produced by microinjections of muscimol into the midbrain raphe nuclei or the ventral tegmental area of the rat. Life Sci 42:775–782
Kreek MJ, LaForge KS, Butelman E (2002) Pharmacotherapy of addictions. Nat Rev Drug Discov 1:710–726
Krupitsky EM, Burakov AM, Ivanov VB, Krandashova GF, Lapin IP, Ja Grinenko A, Borodkin YS (1993) Baclofen administration for the treatment of affective disorders in alcoholic patients. Drug Alcohol Depend 33:157–163
Leggio L, Kenna GA, Swift RM (2008) New developments for the pharmacological treatment of alcohol withdrawal syndrome. A focus on non-benzodiazepine GABAergic medications. Prog Neuro-Psychopharmacol Biol Psychiatry 32:1106–1117
Liu ZH, Ikemoto S (2007) The midbrain raphe nuclei mediate primary reinforcement via GABA(A) receptors. Eur J Neurosci 25:735–743
Maier SF, Watkins LR (2005) Stressor controllability and learned helplessness: the roles of the dorsal raphe nucleus, serotonin, and corticotropin-releasing factor. Neurosci Biobehav Rev 29:829–841
Marcinkiewicz M, Morcos R, Chretien M (1989) CNS connections with the median raphe nucleus: retrograde tracing with WGA-apoHRP-Gold complex in the rat. J Comp Neurol 289:11–35
Moore RY (1981) The anatomy of central serotonin systems in the rat brain. In: Jacobs BL, Gelperin A (eds) Serotonin neurotransmission and behavior. MIT, Cambridge, pp 35–71
Paris JM, Lorens SA (1987) Intra-median raphe infusions of muscimol and the substance P analogue DiMe-C7 produce hyperactivity: role of serotoinin neurons. Behav Brain Res 26:139–151
Paxinos G, Watson C (2005) The rat brain in stereotaxic coordinates, 5th edn. Elsevier, Amsterdam
Przewlocka B, Stala L, Scheel-Krüger J (1979) Evidence that GABA in the nucleus dorsalis raphe induces stimulation of locomotor activity and eating behavior. Life Sci 25:937–946
Serrats J, Artigas F, Mengod G, Cortes R (2003) GABAB receptor mRNA in the raphe nuclei: co-expression with serotonin transporter and glutamic acid decarboxylase. J Neurochem 84:743–752
Shim I, Javaid J, Wirtshafter D (1997) Dissociation of hippocampal serotonin release and locomotor activity following pharmacological manipulations of the median raphe nucleus. Behav Brain Res 89:191–198
Shin R, Cao J, Webb SM, Ikemoto S (2010) Amphetamine administration into the ventral striatum facilitates behavioral interaction with unconditioned visual signals in rats. PLoS ONE in press
Smith D, Gallager D (1987) GABA, benzodiazepine and serotonergic receptor development in the dorsal raphe nucleus: electrophysiological studies. Brain Res 432:191–198
Sofuoglu M, Kosten T (2005) Novel approaches to the treatment of cocaine addiction. CNS Drugs 19:13–25
Stewart JT (1992) A case of mania associated with high-dose baclofen therapy. J Clin Psychopharmacol 12:215–217
Tao R, Ma Z, Auerbach SB (1996) Differential regulation of 5-hydroxytryptamine release by GABAA and GABAB receptors in midbrain raphe nuclei and forebrain of rats. Br J Pharmacol 119:1375–1384
Taylor M, Bhagwagar Z, Cowen PJ, Sharp T (2003) GABA and mood disorders. Psychol Med 33:387–393
Varga V, Sik A, Freund TF, Kocsis B (2002) GABA(B) receptors in the median raphe nucleus: distribution and role in the serotonergic control of hippocampal activity. Neuroscience 109:119–132
Vertes RP (1991) A PHA-L analysis of ascending projections of the dorsal raphe nucleus in the rat. J Comp Neurol 313:643–668
Vertes RP, Martin GF (1988) Autoradiographic analysis of ascending projections from the pontine and mesencephalic reticular formation and the median raphe nucleus in the rat. J Comp Neurol 275:511–541
Wirtshafter D, Trifunovic R (1992) Nonserotonergic control of nucleus accumbens dopamine metabolism by the median raphe nucleus. Pharmcol Biochem Behav 41:501–505
Wirtshafter D, Sheppard AC (2001) Localization of GABAB receptors in midbrain monoamine containing neurons in the rat. Brain Res Bull 56:1–5
Wirtshafter D, Klitenick MA, Asin KE (1987) Evidence against serotonin involvement in the hyperactivity produced by injections of muscimol into the median raphe nucleus. Pharmacol Biochem Behav 27:45–52
Wirtshafter D, Stratford TR, Pitzer MR (1993) Studies on the behavioral activation produced by stimulation of GABAB receptors in the median raphe nucleus. Behav Brain Res 59:83–93
Wolf ME, Almy G, Toll M, Mosnaim AD (1982) Mania associated with the use of baclofen. Biol Psychiatry 17:757–759
Yassa RY, Iskandar HL (1988) Baclofen-induced psychosis: two cases and a review. J Clin Psychiatry 49:318–320
Acknowledgments
This research was supported by the Intramural Research Program of the National Institute on Drug Abuse, National Institutes of Health.
Conflict of interest
We have no financial interest to disclose.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Shin, R., Ikemoto, S. The GABAB receptor agonist baclofen administered into the median and dorsal raphe nuclei is rewarding as shown by intracranial self-administration and conditioned place preference in rats. Psychopharmacology 208, 545–554 (2010). https://doi.org/10.1007/s00213-009-1757-3
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00213-009-1757-3