Functional Correlation Between Feeding-Related Neurons and Chemical Senses

Food and water intake are regulated by glucosesensitive neurons (GSNs) in the lateral hypothalamus (LHA); the firing rates of GSNs decrease in response to glucose administered by electrophoresis [1], and to metabolites, hormones, cytokines, growth factors, and neurotransmitters [2]. About two-thirds of LHA cells are glucose-insensitive neurons (GISNs) and do not respond to these substances. The GISNs respond specifically to environmental visual and auditory signals in tasks to acquire food [3]. Thus endogenous chemical information is processed by GSNs, and external information is processed by GISNs to regulate feeding. Gustatory [4–6] and olfactory [7,8] projections to the LHA have been identified in primates, and both GSNs and GISNs respond to taste and olfaction. This report describes activity changes of single neurons in the LHA of alert rhesus monkeys during a conditioned bar-press feeding task and changes in these responses due to gustation, olfaction, and electrophoretic application of glucose, norepinephrine, and dopamine.