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 fibres of the rat in vitro skin and saphenous nerve preparation with psychophysical measurements of sensibility to cutaneous electrical stimulation in human volunteers. The same clinical diagnostic stimulator and modified skin electrodes were used in both animal and human experiments. Axons were recruited by increasing the stimulus strength, and correlation was made between the stimulus intensity required for unit activation 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 fibres.