The effects of changes in glucose concentration were studied on 256 ventromedial (VMH), 212 dorsomedial (DMH) and 59 lateral (LHA) neurons recorded from coronally-oriented rat hypothalamic slices. When glucose concentration of the medium was increased (5.5-20 mM), these neurons exhibited 3 response patterns: excitation, excitation followed by inhibition, and inhibition. Twenty percent of neurons in VMH, 33% in DMH, and 41% in LHA responded to increases in glucose concentration. The majority in VMH and DMH were excited, and in LHA, inhibited. Only minor modifications of these ratios were obtained by isolating VMH from the other areas. In isolated DMH, equal numbers were excited and inhibited. Both glucose-responsive and non-glucose-responsive neurons in VMH and DMH were identified by intracellular horseradish peroxidase staining. The dendritic arborizations of glucose-responsive neurons were richer than in non-glucose-responsive neurons. These results suggest that the different populations of glucose-responsive neurons in the VMH, DMH and LHA might have different functions in the regulation of glucose.