Glucose responding neurons in the nucleus tractus solitarius of the rat: in vitro study.

Glucose response of 162 neurons in the nucleus tractus solitarius (NTS) was examined in brainstem slices. When glucose was applied by addition to the bath medium or by electrophoresis, approximately 27% of the neurons responded; 20% were glucose-sensitive neurons which decreased in activity and 7% glucoreceptor neurons which increased in activity. Significantly more glucose-sensitive neurons were found in the caudal part than in the rostral part, while non-glucose responding neurons were distributed widely within the NTS. The populations of glucose-sensitive and glucoreceptor neurons were 11% and 5% in the rostral part, and 28% and 8% in the caudal part of the NTS. Intracellular horseradish peroxidase staining of NTS neurons revealed that glucose-sensitive neurons were medium-sized, fusiform or pyramidal cells with many more dendrites than non-responding small oval cells. Specific functional and morphological characteristics of these glucose responding neurons were clarified by this study.