Anatomical Science International

, Volume 89, Issue 4, pp 199–206 | Cite as

Postnatal changes in the number of serotonin-immunoreactive cells in midbrain raphe nuclei of male rats

  • Hiroyuki Ito
  • Tetsuji Moriizumi
  • Yuji Shimogawa
  • Korehito YamanouchiEmail author
Original Article


To clarify the developmental changes in serotonergic neurons in the subdivisions of the dorsal (DR) and median raphe (MR) nuclei before puberty, the extent of the nuclei and the number of serotonin (5-HT) immunoreactive (ir) cells were measured in 5-, 15-, and 30-day-old rats and 8-week-old (adult) castrated male rats. The brains were fixed and 50 μm frozen sections prepared. After immunostaining for 5-HT, the number of 5-HT-ir cells in a 0.2 × 0.2 mm frame in the dorsal, ventral and lateral subdivisions of the DR (dDR, vDR and lDR, respectively) and MR were counted. Total numbers of 5-HT-ir cells counted in the frame of three sections in each rat were expressed as the number of cells per cubic millimeter (density). The results indicated that the densities of 5-HT-ir cells in the MR were almost the same in all age groups. On the other hand, among the subdivisions of the DR, the mean density of 5-HT-ir cells in 15-day-old rats was higher than that in the 5-day-old group in the lDR only. The area of the three sections of the DR and of the MR was also measured. The area of the DR in 15-day-old rats was found to be twice that in the 5-day-old rats, and differed from the area in 30-day-old rats and adults. There were no differences among the age groups in the areas of the MR. The results indicate that the expression of 5-HT in the lDR and extent of the DR increased to adult levels from days 5 to 15 after birth. In the dDR, vDR and MR, expression of 5-HT at postnatal day 5 was at adult levels already.


Dorsal and median raphe nuclei 5-HT immunopositive cell Postnatal development Male rat 



This study was supported by Grants-in-Aid for scientific research from the MEXT of Japan; Kibankeisei (2010).

Conflict of interest



  1. Azmitia EC, Segal M (1978) An autoradiographic analysis of the differential ascending projections of the dorsal and median raphe nuclei in the rat. J Comp Neurol 179:641–667PubMedCrossRefGoogle Scholar
  2. Carlsson M, Carlsson A (1988) A regional study of sex differences in rat brain serotonin. Prog Neuropsychopharmacol Biol Psychiatry 12:53–61PubMedCrossRefGoogle Scholar
  3. De Almeida RM, Lucion AB (1997) 8-OH-DPAT in the median raphe, dorsal periaqueductal gray and corticomedial amygdala nucleus decreases, but in the medial septal area it can increase maternal aggressive behavior in rats. Psychopharmacology 134:392–400PubMedCrossRefGoogle Scholar
  4. Dori I, Dinopoulos A, Blue ME, Parnavelas JG (1996) Regional differences in the ontogeny of the serotonergic projection to the cerebral cortex. Exp Neurol 138:1–14PubMedCrossRefGoogle Scholar
  5. Dori IE, Dinopoulos A, Parnavelas JG (1998) The development of the synaptic organization of the serotonergic system differs in brain areas with different functions. Exp Neurol 154:113–125PubMedCrossRefGoogle Scholar
  6. Gorski RA (1971) Gonadal hormones and perinatal development of neuroendocrine function. In: Martini L, Ganong WF (eds) Frontiers in neuroendocrinology. Oxford University Press, Oxford, pp 237–290Google Scholar
  7. Hyyppǎ M, Lampinen P, Lehtinen P (1972) Alteration in the sexual behaviour of male and female rats after neonatal administration of p-chlorophenylalanine. Psychopharmacologia 25:152–161PubMedCrossRefGoogle Scholar
  8. Ito H, Yamanouchi K (2010) Sex and regional differences in decrease of serotonin-immunoreactive cells by parachlorophenylalanine in rat raphe nuclei. Neurosci Res 67:33–39PubMedCrossRefGoogle Scholar
  9. Kakeyama M, Yamanouchi K (1992) Lordosis in male rats: the facilitatory effect of mesencephalic dorsal raphe nucleus lesion. Physiol Behav 51:181–184PubMedCrossRefGoogle Scholar
  10. Kakeyama M, Yamanouchi K (1993) Female sexual behaviors in male rats with dorsal raphe nucleus lesions: treatment with p-chlorophenylalanine. Brain Res Bull 30:705–709PubMedCrossRefGoogle Scholar
  11. Kakeyama M, Yamanouchi K (1996) Inhibitory effect of baclofen on lordosis in female and male rats with dorsal raphe nucleus lesion or septal cut. Neuroendocrinology 63:290–296PubMedCrossRefGoogle Scholar
  12. Kakeyama M, Umino A, Nishikawa T, Yamanouchi K (2002) Decrease of serotonin and metabolite in the forebrain and facilitation of lordosis by dorsal raphe nucleus lesions in male rats. Endocr J 49:573–579PubMedCrossRefGoogle Scholar
  13. Kanno K, Shima S, Ishida Y, Yamanouchi K (2008) Ipsilateral and contralateral serotonergic projections from dorsal and median raphe nuclei to the forebrain in rats: immunofluorescence quantitative analysis. Neurosci Res 61:207–218PubMedCrossRefGoogle Scholar
  14. Kondo Y, Yamanouchi K (1997) Potentiation of ejaculatory activity by median raphe nucleus lesions in male rats: effect of p-chlorophenylalanine. Endocr J 44:873–879PubMedCrossRefGoogle Scholar
  15. Ladosky W, Gaziri LC (1970) Brain serotonin and sexual differentiation of the nervous system. Neuroendocrinology 6:168–174PubMedCrossRefGoogle Scholar
  16. Lauder JM (1990) Ontogeny of the serotonergic system in the rat: serotonin as a developmental signal. Ann N Y Acad Sci 600:297–313PubMedCrossRefGoogle Scholar
  17. Liu Q, Wong-Riley MT (2005) Postnatal developmental expressions of neurotransmitters and receptors in various brain stem nuclei of rats. J Appl Physiol (1985) 98:1442–1457CrossRefGoogle Scholar
  18. Liu Q, Wong-Riley MT (2008) Postnatal changes in the expression of serotonin 2A receptors in various brain stem nuclei of the rat. J Appl Physiol (1985) 104:1801–1808CrossRefGoogle Scholar
  19. Liu Q, Wong-Riley MT (2010) Postnatal changes in tryptophan hydroxylase and serotonin transporter immunoreactivity in multiple brainstem nuclei of the rat: implications for a sensitive period. J Comp Neurol 518:1082–1097PubMedCentralPubMedCrossRefGoogle Scholar
  20. Loizou LA (1972) The postnatal ontogeny of monoamine-containing neurones in the central nervous system of the albino rat. Brain Res 40(2):395–418PubMedGoogle Scholar
  21. Lu H, Ozawa H, Nishi M, Ito T, Kawata M (2001) Serotonergic neurones in the dorsal raphe nucleus that project into the medial preoptic area contain oestrogen receptor beta. J Neuroendocrinol 13:839–845PubMedCrossRefGoogle Scholar
  22. Maekawa F, Yamanouchi K (1998) Differential effects of dorsal raphe nucleus lesions on pseudopregnancy induced by reserpine or vaginal stimulation in female rats. J Reprod Dev 44:337–343CrossRefGoogle Scholar
  23. Maekawa F, Tsukahara S, Tsukamura H, Maeda KI, Yamanouchi K (1999) Prevention of inhibitory effect of dorsal raphe nucleus lesions on ovulation and LH surge by 5-HT 2A/2C receptor agonists in female rats. Neurosci Res 35:291–298PubMedCrossRefGoogle Scholar
  24. Matsumoto T, Yamanouchi K (1997) Effects of p-chlorophenylalanine on male sexual behavior in female rats with mesencephalic raphe nuclei lesions. Endocr J 44:383–388PubMedCrossRefGoogle Scholar
  25. Mos J, Olivier B, Poth M, Van Oorschot R, Van Aken H (1993) The effects of dorsal raphe administration of eltoprazine, TFMPP and 8-OH-DPAT on resident intruder aggression in the rat. Eur J Pharmacol 238:411–415PubMedCrossRefGoogle Scholar
  26. Nagano M, Liu M, Inagaki H, Kawada T, Suzuki H (2012) Early intervention with fluoxetine reverses abnormalities in the serotonergic system and behavior of rats exposed prenatally to dexamethasone. Neuropharmacology 63:292–300PubMedCrossRefGoogle Scholar
  27. Parent A, Descarries L, Beaudet A (1981) Organization of ascending serotonin systems in the adult rat brain. A radioautographic study after intraventricular administration of [3H]5-hydroxytryptamine. Neuroscience 6:115–138PubMedCrossRefGoogle Scholar
  28. Park DH, Snyder DW, Joh TH (1986) Postnatal developmental changes of tryptophan hydroxylase activity in serotonergic cell bodies and terminals of rat brain. Brain Res 378:183–185PubMedGoogle Scholar
  29. Patisaul HB, Fortino AE, Polston EK (2008) Sex differences in serotonergic but not gamma-aminobutyric acidergic (GABA) projections to the rat ventromedial nucleus of the hypothalamus. Endocrinology 149:397–408PubMedCrossRefGoogle Scholar
  30. Paxinos G, Watson C (2007) The rat brain in stereotaxic coordinates, 6th edn. Academic Press, New YorkGoogle Scholar
  31. Soga T, Wong DW, Putteeraj M, Song KP, Parhar IS (2012) Early-life citalopram-induced impairments in sexual behavior and the role of androgen receptor. Neuroscience 225:172–184PubMedCrossRefGoogle Scholar
  32. Takeoka A, Kubasak MD, Zhong H, Roy RR, Phelps PE (2009) Serotonergic innervation of the caudal spinal stump in rats after complete spinal transection: effect of olfactory ensheathing glia. J Comp Neurol 515:664–676PubMedCentralPubMedCrossRefGoogle Scholar
  33. Takeuchi Y, Kimura H, Sano Y (1982) Immunohistochemical demonstration of the distribution of serotonin neurons in the brainstem of the rat and cat. Cell Tissue Res 224:247–267PubMedCrossRefGoogle Scholar
  34. Törk I (1985) Raphe nuclei and serotonin containing systems. In: Paxinos G (ed) The rat nervous system. Academic Press, Australia, pp 43–78Google Scholar
  35. Ugrumov MV, Taxi J, Mitskevich MS, Tramu G (1986) Development of the hypothalamic serotoninergic system during ontogenesis in rats. Immunocytochemical and radioautographic study. Brain Res 395:75–84PubMedGoogle Scholar
  36. Vertes RP (1991) A PHA-L analysis of ascending projections of the dorsal raphe nucleus in the rat. J Comp Neurol 313:643–668PubMedCrossRefGoogle Scholar
  37. Vertes RP, Fortin WJ, Crane AM (1999) Projections of the median raphe nucleus in the rat. J Comp Neurol 407:555–582PubMedCrossRefGoogle Scholar
  38. Watts AG, Stanley HF (1984) Indoleamines in the hypothalamus and area of the midbrain raphe nuclei of male and female rats throughout postnatal development. Neuroendocrinology 38:461–466PubMedCrossRefGoogle Scholar

Copyright information

© Japanese Association of Anatomists 2013

Authors and Affiliations

  • Hiroyuki Ito
    • 1
    • 2
  • Tetsuji Moriizumi
    • 1
  • Yuji Shimogawa
    • 2
  • Korehito Yamanouchi
    • 2
    Email author
  1. 1.Department of AnatomyShinshu University School of MedicineNaganoJapan
  2. 2.Laboratory of Neuroendocrinology, Department of Human Behavior and Environment Sciences, School of Human SciencesWaseda UniversityTokorozawaJapan

Personalised recommendations