Neurophysiological Response of Single Receptor Units in the Tooth of the Cat

¹ Department of Physiology, School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania

Exploration of exposed dentin of the cat's tooth in the vicinity of the pulp with wire electrodes has made possible recording the electrical responses evoked in receptors specifically sensitive to heat, cold, and touch. Few unit responses have been obtained for heat-sensitive units, while single unit discharges have been studied in response to cold and touch. Estimates of receptor population for a single tooth have led to a value of 10-25 single cold-sensitive units. Frequency of impulse discharge was not directly proportional to temperature of the tooth but showed dependence both on thermal gradient and on specific temperature intervals. Maximum frequency of discharge of a single unit was 50 per second.

Single responses obtained from individual cold-sensitive receptors showed a diphasic spike potential immediately preceded by a receptor prepotential whose appearance did not always lead to a conducted impulse. Responses evoked by light touch on specific spots on the dentin closely resembled those resulting from cold stimulation. Impulses produced on heating the tooth were generally smaller than the cold responses and seldom showed a preceding prepotential.