COMPARISON OF THE SENSORY THRESHOLD IN HEALTHY-HUMAN VOLUNTEERS WITH THE SENSORY NERVE RESPONSE OF THE RAT IN-VITRO HINDLIMB SKIN AND SAPHENOUS NERVE PREPARATION ON CUTANEOUS ELECTRICAL-STIMULATION

We report a comparative study of stimulation thresholds of cutaneous f ibres of the rat in vitro skin and saphenous nerve preparation with ps ychophysical measurements of sensibility to cutaneous electrical stimu lation in human volunteers. The same clinical diagnostic stimulator an d modified skin electrodes were used in both animal and human experime nts. Axons were recruited by increasing the stimulus strength, and cor relation was made between the stimulus intensity required for unit act ivation and their conduction velocities. The findings suggest that an initial ''tingling'' sensation is due to recruitment of A beta fibres and that later sharp ''pricking'' occurs with recruitment of A delta f ibres.