Gonadal hormones are important regulators of sexual differentiation of the CNS. Exposure to testosterone and estrogen during development causes permanent organizational differences between males and females. We previously described functional sex-related differences of the GABAAergic circuits of the rat substantia nigra pars reticulata (SNR) involved in the control of flurothyl seizures. This sexual differentiation of the SNR is regulated by postnatal testosterone. To assess whether the organizing effects of testosterone in the SNR are mediated via the androgen receptor (AR) and/or estrogen receptors (ER), we used immunohistochemistry to study the ontogeny of AR, ERα and ERβ expression in SNR and substantia nigra pars compacta (SNC) of male and female rats. Rats on the day of birth [postnatal day (PN) 0] and at PN1, PN5, PN15 and PN30 were used. AR- and ERβ-immunopositive cells were present in SNR and SNC in both sexes and at all ages. ERα was not detected in male and female SNC at PN0-PN1. In both substantia nigra (SN) regions, there were developmentally regulated sex differences in AR, ERα and ERβ immunoreactivity. In the SN, each receptor showed specific intracellular localization: AR was present in the nucleus, ERα and ERβ were present both in nuclear and extranuclear compartments. ERα was detected also in processes. At PN0-PN1, quantitative analysis revealed sex and regional differences in the distribution of SN cells expressing AR and ERα, while ERβ were equally present in both sexes. The presence of gonadal steroid receptors in the SN suggests that the biological effects of gonadal hormones in the CNS extend beyond reproduction-related functions and may affect and modify motor behaviors (including seizures) in a sex-specific manner. Based on the ontogeny of SNR ERβ, we hypothesize that postnatal injections of testosterone may regulate the nigral GABAA system through the aromatization pathway and activation of ERβ.
|Original language||English (US)|
|Number of pages||12|
|State||Published - Dec 9 2002|
- Gonadal steroid receptors
- Protein expression
- Sexual dimorphism
ASJC Scopus subject areas