Blood glucose selectively affects taste-evoked activity in rat nucleus tractus solitarius

Gustatory afferent activity and the perceptions it evokes have proven to be modifiable by physiological needs. We monitored changes in taste responses in the rat nucleus tractus solitarius (NTS) as a function of blood glucose levels. Taste stimuli were 0.1 M NaCl, 1.0 M glucose, 0.03 M HCl and 0.01 M QHCl. Gustatory activity was selectively modified as an inverse function of blood glucose. Intravenous injections caused blood glucose levels to rise from 90 to near 200 mg% 5-15 min post-injection, with slow recovery thereafter. During the 5-15 min period, NTS responses to glucose were depressed an average 43%, NaCl by 20%, HCl by 16% and QHCl by 3%. Time courses of all responses were unmodified. This effect, probably mediated either by glucoreceptors in NTS or by vagal afferents from the gut, suggests a particular suppression of more appetitive tastes, and so may provide a neural concomitant to the decreased appeal of food which accompanies satiety.