RELATIONSHIPS BETWEEN THE MORPHOLOGY AND FUNCTION OF GASTRIC-SENSITIVE AND INTESTINE-SENSITIVE NEURONS IN THE NUCLEUS OF THE SOLITARY TRACT

This study employed single cell recording and intracellular iontophore tic injection techniques to characterize and label gastric- and/or int estine-sensitive neurons in the rat nucleus of the solitary tract (NST ). It was possible to divide our sample of NST neurons into three broa d groups based on their response to increased intra-gastric and intra- duodenal pressure. Group 1 cells (N = 14) were excited by duodenal dis tention but were not responsive to gastric stimulation. Most of these intestine-sensitive neurons exhibited a delayed tonic response to the stimulus. Group 2 neurons (N = 13) were excited by gastric distention but were not sensitive to distention of the duodenum. The typical Grou p 2 neuron evidenced a rapid, phasic response to the distention stimul us. Group 3 neurons (N = 29) responded to both gastric and duodenal st imulation. We found that the Group 2 neurons had greater dendritic len gth and more dendritic branch segments than the Group 1 or Group 3 neu rons. Most of the Group 1 neurons were found in the subpostremal/commi ssural region of the NST, while the majority of the Group 2 neurons we re in the gelatinous subnucleus and a disproportionate number of the G roup 3 neurons were located in the medial subnucleus. The results of t his investigation demonstrate that 1) there are relationships between the morphology and physiology of distention-sensitive neurons in the N ST, and 2) there are distinct functional differences between the gelat inous, medial and commissural subnuclei of this nucleus. (C) 1995 Wile y-Liss, Inc.