The significance of small pulses of gonadotrophin-releasing hormone

Abstract

A series of experiments was conducted to ascertain the significance of 'small' pulses of gonadotropin-releasing hormone (GnRH). In the first experiment, ovariectomized hypothalamo-pituitary disconnected (HPD) ewes were given 250 ng pulses of GnRH every 2 h for 1 week, 25 ng pulses every 2 h for 24 h, 25 ng pulses hourly for 24 h and then alternating hourly pulses of 25 and 250 ng. During the 25 ng pulses, LH was not detectable in plasma and FSH concentrations declined after 2 days. Following the 25 ng pulses, the resumption of 250 ng pulses led to exaggerated LH responses (mean ± S.E.M. pulse amplitude 18.7±1.7 vs 10.2±1.2 μg/l in the first week). In a second experiment, ovariectomized-HPD e..