Olfactory coding in the monkey lateral hypothalamus: behavioral and neurochemical properties of odor-responding...

The activity of glucose-sensitive (GS) and glucose-insensitive (GIS) neurons was recorded in the lateral hypothalamic area (LHA) of monkeys during olfactory stimulation, a conditioned alimentary bar press task, and microelectrophoretic application of catecholamines. Olfactory stimuli evoked response of 88% of the GS neurons, and 52% of the GIS cells responded to odors. The GS neurons were more broadly tuned across odorants than the GIS cells, and their responses to various smells with distinct hedonic value were also differential. The odor-responding GS neurons were depressed during the bar press and reward periods of the task, and were mainly inhibited by dopamine. The odor-responding GIS cell activity increased in response to cue light and tone, and was facilitated by dopamine. Histological examinations disclosed topographic dissociation of the odor-responding GS and GIS cells: the former were located in more ventromedial regions than the latter. The results indicate that the GS neurons integrate multiple chemosensory inputs from both endogenous and exogenous sources in the regulation of feeding: whereas the GIS cells distinguish among fewer, more specific cues to control food acquisition behavior.