Effect of Melatonin and Superior Cervical Ganglioectomy on Luteinizing Hormone on Release Induced by Estradiol-Progesterone in Castrated Rats

Abstract
The effect of melatonin on luteinizing hormone (LH) release 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 g/100 g body weight) being stimulatory and the highest (250 g/100 g body weight) inhibitory. Superior cervical ganglionectomy negated the inhibitory effect of the high melatonin 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.