Effect of melatonin on photoperiod responses, ovarian secretion of oestrogen, and coital responses in the domestic cat
Leyva, H.; Madley, T.; Stabenfeldt, G.H.
Journal of Reproduction and Fertility. Supplement 39: 135-142
1989
ISSN/ISBN: 0449-3087 PMID: 2621722 Document Number: 327947
In the 1st of 3 experiments, female cats were treated with 5 mg melatonin every other day while under a photoperiod stimulatory (24-h light:0-h darkness; 24L:0D) or inhibitory (8L:16D) for ovarian activity. Melatonin suppressed ovarian follicle development in animals exposed to 24L:0D during a 60-day study. However, melatonin did not block perception of the 24L:0D regime, since there was increased oestrogen synthesis during ovarian follicular cycles immediately after the end of treatment, compared with the 45 days normally required for a response to 24L:0D. The administration of melatonin to animals kept in 8L:16D resulted in 3 of 4 animals becoming sexually receptive, with normal follicular growth patterns beginning about 70 days into the treatment period. In the 2nd experiment, the administration of 5 mg melatonin on the 2nd day of follicle growth resulted in suppression of oestrogen synthesis. In the 3rd experiment, melatonin treatment decreased the amount of LH released in response to coitus on the 3rd day of oestrus, although the difference was not significant. Melatonin treatment increased the duration of sexual refractoriness after coitus.