VARIABLE PATTERNS OF GONADOTROPIN-RELEASING-HORMONE SECRETION DURING THE ESTROGEN-INDUCED LUTEINIZING-HORMONE SURGE IN OVARIECTOMIZED EWES

Abstract

There have been a number of studies of GnRH secretion into the hypophysial portal blood at the time of the estrogen-induced LH surge, but the exact pattern of secretion at the onset of the positive feedback event remains a point of some dispute. In the present study, GnRH concentrations in portal plasma and jugular venous LH concentrations were measured in samples taken at 2.5-min intervals from five ovariectomized control ewes and seven ovariectomized ewes that were treated with 50 micrograms estradiol benzoate (im) to cause a LH surge. The frequency of GnRH pulses was calculated using a modification of previous criteria because of the frequent sampling. It was found that GnRH pulse frequen..