Failure of melatonin to influence endogenous opioid effects on LH secretion in the anoestrous ewe.


In May mature seasonally anoestrous ewes were implanted with melatonin which advanced the onset of cycles by about 1 month. The LH response to an opioid antagonist, WIN-3, was determined 5, 15, 25 and 60 days after melatonin implantation, by intravenous administration of WIN-3 (12.5 mg/dose) 4 times at 15-min intervals during both the 1st and the 5th hour… (More)