title: Gender and gonadal status modulation of dorsal raphe nucleus serotonergic neurons. Part I: effects of gender and pregnancy.
abstract: Gender differences in susceptibility to affective disorders are well documented. The ovarian steroids, estrogen (E) and progesterone (P), may modulate the function of the serotonergic (5-HT) system, implicated in the etiology and treatment of affective disorders. We tested the hypothesis that ovarian steroid modulation of 5-HT function could result in a modification of the 5-HT neuronal firing activity. Extracellular unitary recordings of dorsal raphe nucleus 5-HT neurons were obtained in male rats and in female rats during natural E and P fluctuations. The average firing activity of 5-HT neurons was significantly higher in males (41%) than in freely cycling (CF) and in ovariectomized (OVX) females. During pregnancy, it increased gradually and by up to 136% on gestational day 17, then declined before parturition. In the postpartum period (PP), the firing rate decreased markedly compared to P17 but remained 63% higher than in CF. During pregnancy, the firing rate variations were closely correlated with P plasmatic levels. Finally no modification of the basal firing activity of locus coeruleus noradrenergic neurons was found in any group tested. Our results thus reveal a gender and pregnancy-dependent modulation of 5-HT firing rate that would impact 5-HT-mediated neurotransmission.
authors.affiliation: McGill University, Department of Psychiatry, 1033 Pine Avenue West, Montreal, Quebec, Canada H3A 1A1.
authors.forename: R
authors.initials: R
authors.lastname: Klink
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; D000818:Animals; D004967:Estrogens / Q000097:blood; D005260:Female; D008297:Male; D009474:Neurons / Q000502:physiology*; D010052:Ovariectomy; D011247:Pregnancy / Q000097:blood / Q000502:physiology*; D011374:Progesterone / Q000097:blood; D011903:Raphe Nuclei / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012701:Serotonin / Q000502:physiology*; D012727:Sex Characteristics
chemical_list: D004967:Estrogens; D012701:Serotonin; D011374:Progesterone