GLUCOSE-SENSITIVE NEURONS OF THE GLOBUS-PALLIDUS .2. COMPLEX FUNCTIONAL ATTRIBUTES

The globus pallidus (GP) is intimately involved in regulation of vario us aspects of hunger- and thirst-motivated behaviors. Our parallel neu rochemical studies demonstrated the existence of GP neurons whose disc harge rates are suppressed by glucose applied microelectrophoretically . In the present series of experiments, we aimed to provide complex, f eeding-associated functional characterization-similar to that previous ly accomplished in the case of lateral hypotharamic and amygdaloid che mosensitive neurons-of these glucose-sensitive (GS) and the glucose-in sensitive (GIS) pallidal cells. To do so, extracellular single neuron activity of the GP was recorded in anesthetized rats and anesthetized or awake rhesus monkeys by means of carbon fiber, multibarreled glass microelectrodes during: a) microelectrophoretic administration of chem icals, b) gustatory, and c) olfactory stimulations. In alert primates, activity changes were also recorded during presentation of food and n onfood objects as well as during the performance of a conditioned, hig h fixed-ratio bar-press feeding task. The half of pallidal cells exami ned showed firing rate changes during phases of the conditioned alimen tary task. In both species, about 1/7 of all neurons tested proved to be GS, while the proportion of cells responding to gustatory and olfac tory stimulations was 19% and 16%, respectively. Task-related and tast e- and smell-responsive units were mainly found among the GS neurons o f the pallidum, These data, along with previous findings, indicate tha t chemosensitive cells of the GP, in an apparent overlap with units of the central gustatory representation, are involved in a hierarchicall y organized glucose-monitoring neural network, through which pallidal neurons exert their integrative functions in the central feeding contr ol,