RELATIONSHIPS BETWEEN THE MORPHOLOGY AND FUNCTION OF GASTRIC AND INTESTINAL DISTENSION-SENSITIVE NEURONS IN THE DORSAL MOTOR NUCLEUS OF THEVAGUS

The activity of vagal motor neurons is influenced by sensory informati on transmitted to the brainstem. In particular, there is evidence that distention of the stomach increases activity of motor neurons in the dorsal vagal motor nucleus, whereas distention of the duodenum, small intestine, and colon reduces neuron firing. In this study, we determin ed 1) the response of vagal motor neurons to distention of the stomach and duodenum and 2) whether the response properties were associated w ith specific morphological features. Using the single-cell recording a nd iontophoretic injection technique, we identified four groups of vag al motor neurons affected by gastric and/or duodenal distention. Group 1 neurons responded to either gastric or duodenal stimulation. Neuron s in groups 2, 3, and 4 were affected by both gastric and duodenal dis tention. Group 2 neurons were excited by duodenal distention and were inhibited by gastric distention. Group 3 neurons were inhibited by duo denal distention and were excited by gastric distention. Most neurons belonged to group 4. Neurons in this group were inhibited by both gast ric and duodenal distention. Our analyses revealed that the neurons af fected by both stimuli had distinctive structural features. Neurons in group 2 had the largest somata, the most dendritic branches, and the greatest cell surface area. Neurons in group 3 were the smallest and h ad the shortest dendritic length. In addition, we were able to demonst rate that; the neurons in group 4 had a smaller total dendritic length and a smaller cell volume than neurons in group 2 and had more dendri tic branch segments than neurons in group 3. These results suggest tha t morphological features are associated with specific response propert ies of vagal motor neurons. (C) 1996 Wiley-Liss, Inc.