Quantitative and qualitative effects of ethanol on the LHRH-LH axis of the rat

Ethanol (ETOH) has been shown to have pronounced effects on reproductive endocrinology in humans as well as laboratory animals. We have studied the effects of ETOH on the hypothalamic-pituitary-luteinizing hormone (LH) axis, using the male rat as an animal model. In order to better understand the method by which ETOH depresses plasma LH levels, we have used both quantitative and qualitative methods to analyze the effects of ETOH on hypothalamic luteinizing hormone-releasing hormone (LHRH). As measured by RIA, both saline and ETOH-treated rats showed a decrease in hypothalamic LHRH content with a concomitant increase in plasma LH; however, the animals treated with ETOH retained significantly greater concentrations of LHRH and showed significantly lower plasma LH levels when compared to saline-treated controls. In addition, ETOH-treated intact animals showed significant increases in LHRH content, with LH levels remaining significantly lower than the saline-treated intact controls. Immunocytochemical assessment of the relative content of LHRH within each group concurred with the results obtained using RIA. These data as well as other data obtained from other laboratories indicate that alcohol-induced decreases in LH levels are due to a diminished release rate of hypothalamic LHRH.