Evidence for 5-HT2 receptor involvement in the stimulation of preovulatory LH and prolactin release and ovulation in normal cycling rats.
The participation of serotonin (5-HT) in the control of LH secretion and ovulation has been reported in numerous pharmacological experiments, although the results have been contradictory. In this study to determine the physiological involvement of 5-HT2 receptors in the control of preovulatory LH and prolactin (PRL) release and ovulation, ketanserin (KET), a selective 5-HT2 receptor antagonist, was administered to normal cycling rats. Oral administration of KET at 10 mg/kg BW between 0900h and 1300h on the day of proestrus completely blocked ovulation, while the administration after 1500h did not. The ovulation was confirmed 2 days after treatment with KET. There was no consistent effect on the number of ova ovulated. Co-administration of KET with 5-methoxy-N,N-dimethyltryptamine (5-MeDMT), a 5-HT agonist, at a dose of 2 mg/kg BW ip reversed KET-induced inhibition of ovulation. The highest rate (89%) of reversal was obtained by co-administration at 1500h. KET administered at 1100h completely blocked the preovulatory surge of LH and PRL observed in control animals at 1800h. The present study suggests that 5-HT stimulates preovulatory LH and PRL surge and ovulation via 5-HT2 receptor under physiological conditions and that the effect of 5-HT depends on the critical period and the 24-hour periodicity.
Tanaka
E
E
Toxicology Laboratory, Mitsubishi Kasei Corporation, Yokohama, Japan.
Baba
N
N
Toshida
K
K
Suzuki
K
K
D000818:Animals; D004305:Dose-Response Relationship, Drug; D005260:Female; D007650:Ketanserin / Q000494:pharmacology; D007986:Luteinizing Hormone / Q000097:blood*; D008732:Methoxydimethyltryptamines / Q000494:pharmacology; D010060:Ovulation / Q000187:drug effects / Q000502:physiology*; D011388:Prolactin / Q000097:blood*; D051381:Rats; D017208:Rats, Wistar; D011985:Receptors, Serotonin / Q000502:physiology*; D012702:Serotonin Antagonists; D013997:Time Factors
D008732:Methoxydimethyltryptamines; D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; D011388:Prolactin; D007986:Luteinizing Hormone; D007650:Ketanserin