INVOLVEMENT OF THE GASTRIC VAGAL NERVE IN THE SUPPRESSION OF PULSATILE LUTEINIZING-HORMONE RELEASE DURING ACUTE FASTING IN RATS

Acute fasting has been shown to impair gonadotropin secretion in an estrogen-dependent manner in rats. The present study examined whether the vagus nerves have some role in the suppression of pulsatile LH release after 48-h fasting in ovariectomized estradiol-treated rats by performing complete subdiaphragmatic cutting of the nerves or selective sectioning of its branches (gastric, hepatic, or celiac) after the first hour of a 3-h blood sampling period. Vagotomy, alone, did not cause any changes in LH release in the unfasted animals. However, complete and gastric vagotomies restored pulsatile LH release that was suppressed before the nerves were cut in fasted animals. Neither hepatic nor celiac vagotomy restored pulsatile LH release, which remained suppressed throughout the sampling period in fasted animals. These results suggest that some mechanism involving the afferent vagal nerves, particularly the gastric vagus, has a major role in the suppression of pulsatile LH release during acute fasting in ovariectomized estradiol-primed rats.