Olfactory and visceral projections to the nucleus of the solitary tract

Electrophysiological studies were performed to determine if neurons of the nucleus of the solitary tract (NTS) which receive inputs from the stomach via vagal afferents also respond to olfactory bulb (OB) stimulation. The frequency of neuronal activity of the rostral ventral portion of the NTS was increased by gastric distension (GD). The evoked potentials in the same site due to vagal stimulation displayed short latencies; whereas, the evoked potentials in the dorsomedial part of the NTS due to vagal stimulation had considerably longer latencies. Gastric distension decreased neuronal activity in the dorsomedial NTS. Evoked potentials and increases in neuronal activity were also observed in the dorsomedial NTS due to electrical stimulation. In the dorsomedial NTS, OB stimulation enhanced the decrease in neuronal activity due to GD. Olfactory and visceral functions apparently interact in the NTS in modulating taste mechanisms involved in food selection and ingestion.