Gonadotrophin release induced by Gn-RH or progesterone in female rats maintained on high or low levels of feed intake

Department of Oral Biology, University of Manitoba, Winnipeg, Manitoba R3E0W3, Canada Underfeeding in the female rat results in ovarian atrophy (Piacsek & Meites, 1967; Howland, 1971a) which appears to be related to reduced basal serum levels of LH (Howland, 1971b, 1972; Gombe, Apgar & Hansel, 1973). The observation that ovariectomized underfed rats are capable of maintaining high serum levels of gonadotrophins (Howland, 1971c; Howland & Ibrahim, 1973) suggests that the hypothalamus, if not inhibited, can stimulate the pituitary to secrete gonadotrophins at rates higher than those necessary to maintain normal basal levels in the serum. It is still possible, however, that pituitary responsiveness to hypothalamic hormones is altered in underfed rats or that the ability of the hypothalamus to release sufficient amounts of Gn-RH to cause an ovulatory surge of LH is impaired. The present study was therefore conducted to compare the effect of high or low feed levels on