Frequency Modulation of Pulsatile Luteinizing Hormone-Releasing Hormone Stimulation Can Alter the Effectiveness of Direct Androgen Feedback on Luteinizing Hormone-Releasing Hormone-Induced Luteinizing Hormone Release*

Abstract

A previous study in phenobarbital-treated male rats (1) indicated that both orchidectomy and dihydrotestosterone (DHT) treatment could act directly on the pituitary to modify LH release in response to infused LHRH. These feedback effects did not modify the initial phase of the response to LHRH but became evident during the phase of augmented LH release which began between 60–120 min after the onset of the LHRH stimulus, presumably as a result of LHRH self-priming during the first hour. The present study was done to determine whether similar results would be obtained if LHRH was administered as a series of pulses instead of by continuous infusion. Male rats with iv cannulae were given phenobarbital, then castrated, and immediately given DHT or control implants sc. Three hours later, each rat was given the first of a series of hourly or half-hourly LHRH injections via the cannula. As with LHRH infusion, the initial responses to LHRH were not modified by the presence or absence of DHT. Development of augment...