Electrophysiologic properties and role of the vagal thermoreceptors of lower esophagus and stomach of cat.

Vagal unitary discharges were elicited in anesthetized cats by thermal stimulation of the lower thoracic esophagus and stomach. Discharges were recorded from the nodose ganglion, using extracellular glass microelectrodes. Three types of receptors were distinguished according to the temperature ranges at which they discharged: the cold receptors (10 degrees-36 degrees C), the warm receptors (39 degrees-50 degrees C), and the mixed receptors (10 degrees-35 degrees C and 40 degrees-50 degrees C). All endings were connected to unmyelinated fibers (conduction velocities around 1 m/s). These receptors are stimulated neither by mechanical (strong distention, localized stroking of mucosa) nor by chemical (acid and glucose solutions) stimuli. Therefore they must be considered as true thermoreceptors. Stimulation of the esophageal and gastric thermoreceptors produced changes both in esophageal motility and in respiratory frequency. It was concluded that they are involved in coordination of digestive activity as well as in thermoregulation.