INVESTIGATION OF THE MECHANISM BY WHICH INSULIN-INDUCED HYPOGLYCEMIA DECREASES LUTEINIZING-HORMONE SECRETION IN OVARIECTOMIZED EWES

Abstract

Ovariectomized ewes were treated with 100 IU insulin, iv, which caused reductions in blood sugar and plasma LH concentrations. The effect was prevented by the infusion (iv) of glucose, suggesting that neuroglycopenia and not a direct action of insulin was the cause of reduced LH secretion. An iv infusion of naloxone (40 mg/h for 2 h), which commenced 25 min before the insulin injection, blocked the inhibitory effect of insulin on LH secretion, but it did not prevent the decrease in plasma glucose concentrations. In this treatment group and in a group treated only with naloxone, the opioid antagonist significantly stimulated LH secretion. To determine whether CRF might be involved in the insu..