Effect of melatonin and superior cervical ganglioectomy on luteinizing hormone on release induced by estradiol-progesterone in castrated rats.

The effect of melatonin on luteinizing hormone (LH) relase was studied in castrated female rats injected with estradiol and progesterone. Melatonin administered s.c. twice daily for 6 days exerted a biphasic, dose-related effect on LH release, the lowest dose (125 micrograms/100 g body weight) being stimulatory and the highest (250 micrograms/100 g body weight) inhibitory. Superior cervical ganglionectomy negated the inhibitory effect of the high metatonin dose on steroid-induced LH release. Rather melatonin injection to ganglionectomized rats resulted in significantly higher serum LH values than those of animals injected with estradiol and progesterone alone. Melatonin treatment failed to modify postcastration serum LH levels.