LIMINAL AND SUPRALIMINAL RESPONSE CHARACTERISTICS OF MECHANORECEPTORS OF THE HAIRY AND FOOT PAD SKIN OF CAT DETERMINED WITH SHORT TACTILE PULSES

¹ New York University School of Medicine, Department of Physiology, New York City, NY 10016, U.S.A.
² Department of Physiology, University of Helsinki, Siltavuorenpenger 20 J, SF-00170 Helsinki 17, Finland

The liminal and supraliminal response characteristics of mechanoreceptive units innervating the hairy skin and glabrous foot pad of the cat were determined with single pulses of varying frequency (20, 60 and 150 Hz) in order to compare the characteristics of mechanoreceptors in cat and man. Altogether 172 units were tested. The units were divided into slowly adapting (s.a.) (I and II), rapidly adapting (r.a.) and pacinian (p.c.) units. No hairy skin p.c. units were encountered. The absolute thresholds and supraliminal responses of units innervating the hairy skin resembled those of human hairy skin mechanoreceptors, the s.a. II units having the lowest thresholds and both s.a. and r.a. units having lower thresholds as a function of increasing frequency of the pulse. The results suggest that on the hairy skin detection thresholds are based on activation of mainly s.a. II units, whereas the role of r.a. units is of importance for distinct touch and supraliminal sensations. S.a. units of foot pads were different if compared to s.a. units of human glabrous skin. R.a. and p.c. units in foot pads were similar to corresponding human units and the low detection and touch thresholds on the glabrous skin are explicable on the response properties of r.a. and p.c. units. According to the present study the results concerning response characteristics of cat hairy skin s.a. and r.a. units and cat glabrous skin r.a. and p.c. units can be applied to human psychophysical studies in the corresponding areas.