Gender and gonadal status modulation of dorsal raphe nucleus serotonergic neurons. Part I: effects of gender and pregnancy.
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.
Klink
R
R
McGill University, Department of Psychiatry, 1033 Pine Avenue West, Montreal, Quebec, Canada H3A 1A1.
Robichaud
M
M
Debonnel
G
G
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
D004967:Estrogens; D012701:Serotonin; D011374:Progesterone