CUTANEOUS THERMORECEPTORS IN PRIMATES AND SUB-PRIMATES

1. Cutaneous thermoreceptors were examined electrophysiologically in primates (monkey, baboon) and in sub‐primates (dog and rat) by recording from single units dissected from peripheral nerves. 2. Thermal stimuli were delivered from thermodes in contact with the skin. 3. Primate ‘cold’ receptors had spot‐like receptive fields and were found in both hairy and glabrous skin. The conduction velocities of the axons ranged from 0·6 to 15·3 m/sec. 4. The discharge from the primate receptors characteristically appeared in bursts with intervals of silence within the range temperatures of 18‐40° C. Static and dynamic sensitivity curves were established, with maxima about 30° C. 5. Cold receptors in the lip of the dog had maximal sensitivity at 31‐37° C. The axons were myelinated with conduction velocities less than 20 m/sec. 6. ‘Warm’ receptors, with maximal sensitivity at 40° C and non‐myelinated axons, were abundant in the scrotal nerve of the rat. The ‘cold’ receptors had maximal responses at 23‐28° C. 7. The ‘spurious’ thermoreceptor behaviour of slowly adapting mechanoreceptors is described and the way in which they may distort integrated potential records from whole nerves is analysed. © 1969 The Physiological Society