CHARACTERISTICS OF GLYCEMIA-SENSITIVE NEURONS IN THE NUCLEUS-TRACTUS-SOLITARII - POSSIBLE INVOLVEMENT IN NUTRITIONAL REGULATION

Single unit responses to moderate glycemic variations were extracellul arly recorded in the caudal division of the nucleus tractus solitarii of rats anesthetized by IV infusion of ketamine. As previously observe d, a majority of recorded neurons (70%) were either activated or depre ssed by moderate hyperglycemia. Responses were consistently reproducib le and amplitude was dependent on the maximum level of hyperglycemia. All glycemia-sensitive neurons responded in opposite directions to ind uced hyperglycemia and hypoglycemia, and almost all displayed the same type of response to local and IV glucose administration. Most glycemi a-sensitive neurons were depressed by iontophoresis of clonidine, sugg esting that they were adrenergic or noradrenergic. Based on these find ings, we speculate that glycemia-sensitive neurons in the caudal nucle us tractus solitarii may act as glucose sensors that transmit glycemic information corresponding to different nutritional states, as well as other relevant signals toward hypothalamic structures involved in fee ding and metabolic regulation via ascending adrenergic and noradrenerg ic pathways. Copyright (C) 1996 Elsevier Science Inc.