Effects of Gonadal Hormones on the Hypothalamic Multi-Unit Response to Glucose and Saline in the Rat

The role of gonadal hormones in modulating the hypothalamic multi-unit activity (MUA) response to glucose and saline was studied in normal and gonadectomized male and female rats. In intact male rats, unlike intact females, all hypothalamic placements showed either an increase or a decrease in MUA following an injection of glucose. Gonadectomy alone did not produce a significant change in the pattern of hypothalamic response to glucose. Daily injections of estradiol-17beta resulted in a significant increase in the number of hypothalamic sites that did not show a glucose-induced change in MUA. In general, the effects on saline tended to parallel those on glucose, although the changes were not as extensive. The results are discussed of estradiol modulation of body weight (b.w.) and of the hypothalamic responsiveness to various stimuli, including glucosse and saline injections.