Progesterone stimulates sexual behaviour in female rats by increasing 5-HT activity on 5-HT2 receptors.
We have investigated the possibility that there is a correlation between female sexual receptivity and CNS serotonergic activity. In ovariectomized rats primed with a submaximal steroid regime of 2 micrograms oestradiol benzoate (OB) plus 0.2 mg progesterone (P), so that only a proportion were receptive, the 5-hydroxyindoleacetic acid:5-hydroxytryptamine (5-HT) ratio in the hypothalamus was greater in the receptive compared to the non-receptive rats. When rats were primed with 10 micrograms OB alone, there was no difference in 5-HT activity in the receptive and non-receptive animals. Depletion of hypothalamic 5-HT levels by p-chlorophenylalanine methyl ester (PCPA) inhibited behaviour normally induced by OB plus P and this could be reversed by 5-hydroxytryptophan. PCPA had no effect in animals made receptive by OB alone. This indicates that P, but not OB, exerts its stimulatory effect on sexual behaviour via increasing 5-HT activity. Administration of 5-HT into the lateral, but not 3rd ventricle stimulated sexual behaviour and systemic injection of the selective 5-HT1 and 5-HT2 agonists, Ru 24969 and MK 212, inhibited and stimulated behaviour, respectively. It is suggested that 5-HT has a dual effect on female sexual receptivity acting via different systems, the inhibitory tract acting on 5-HT1 and the stimulatory tract on 5-HT2 receptors.
Wilson
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CA
Hunter
A J
AJ
D000818:Animals; D001923:Brain Chemistry / Q000187:drug effects; D004958:Estradiol / Q000494:pharmacology; D005260:Female; D006897:Hydroxyindoleacetic Acid / Q000032:analysis; D007031:Hypothalamus / Q000502:physiology*; D011374:Progesterone / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D011985:Receptors, Serotonin / Q000502:physiology*; D012701:Serotonin / Q000032:analysis / Q000502:physiology*; D012726:Sexual Behavior, Animal / Q000187:drug effects* / Q000502:physiology
D011985:Receptors, Serotonin; D012701:Serotonin; D011374:Progesterone; D004958:Estradiol; D006897:Hydroxyindoleacetic Acid