title: Oestrogen and testosterone modulate the firing activity of dorsal raphe nucleus serotonergic neurones in both male and female rats.
abstract: Women are twice as likely to suffer from mood disorders than men. Moreover, a growing body of evidence suggests a reciprocal modulation between sex steroids and the serotonin (5-HT) system. A previous study from our laboratory has shown that the progesterone metabolites 5beta-pregnane-3,20-dione (5beta-DHP) and 5alpha-pregnan-3alpha-ol,20-one (3alpha,5alpha-THP), as well as dehydroepiandrosterone (DHEA), increase the firing activity of dorsal raphe nucleus (DRN) 5-HT neurones in female rats. The present study was undertaken to assess the effects of these steroids in male rats, as well as the effects of testosterone and 17beta-oestradiol (17beta-E) in both sexes, and finally to evaluate gender differences in the modulation of the 5-HT neuronal firing activity by these different neuroactive steroids. Male rats were treated i.c.v., for 7 days, with a dose of 50 microg/kg/day of one of the following steroids: progesterone, 5beta-DHP, 3alpha,5alpha-THP, DHEA, testosterone, 17beta-hydroxy-5alpha-androstan-3-one (5alpha-DHT) and 17beta-E. Some rats also received a 3-day administration of testosterone (50 microg/kg/day, i.c.v). Females were treated in the same fashion with testosterone and 17beta-E. Extracellular unitary recordings of 5-HT neurones, obtained in vivo in the DRN of these rats, revealed that testosterone and 17beta-E increased the firing activity of 5-HT neurones in both males and females. In males, the effect of testosterone could already be seen after 3 days of treatment. Neither castration nor any treatment with other steroids significantly modified the firing rate of male 5-HT neurones. Taken together with previous findings, the results of the present study indicate both similarities and differences between sexes in the modulation of 5-HT neurones by some steroids. This could prove important in understanding gender differences in mood disorders.
authors.affiliation: Department of Psychiatry, McGill University, Montréal, Québec, Canada.
authors.forename: M
authors.initials: M
authors.lastname: Robichaud
authors.forename: G
authors.initials: G
authors.lastname: Debonnel
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000704:Analysis of Variance; D000818:Animals; D004594:Electrophysiology; D004958:Estradiol / Q000008:administration & dosage / Q000502:physiology*; D005260:Female; D012739:Gonadal Steroid Hormones / Q000008:administration & dosage / Q000502:physiology; D007276:Injections, Intraventricular; D008297:Male; D009474:Neurons / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D011903:Raphe Nuclei / Q000166:cytology / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012701:Serotonin / Q000378:metabolism*; D012737:Sex Factors; D013739:Testosterone / Q000008:administration & dosage / Q000502:physiology*
chemical_list: D012739:Gonadal Steroid Hormones; D012701:Serotonin; D013739:Testosterone; D004958:Estradiol