Analysis of cutaneous warm and cold fibres in primates
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Cutaneous warm and cold receptors were examined electrophysiologically in rhesus monkeys (Macaca mulatta) by recording from single units dissected from the saphenous nerve and the superficial branch of the radial nerve. Single warm and cold fibres had spot-like receptive fields in the hairy skin which were highly specific to thermal stimuli and did not respond to mechanical deformation of the skin. One group of cutaneous warm receptors had a range of static activity between 30 and 44°C and an average static maximum of 12 imp/sec at 41°C, whereas the static maximum of the other group was at temperatures higher than 44°C. About one third of the cold fibres was myelinated, with a conduction velocity from 2.2 to 9.5 m/sec (mean 6.3 m/sec), while the remaining part was unmyelinated, having a conduction velocity of 0.3 to 1.3 m/sec (mean 0.7 m/sec). All warm fibres were non-myelinated, with a conduction velocity of 0.4 to 0.9 m/sec (mean 0.7 m/sec).
Key wordsThermoreceptors Warm Fibres Cold Fibres Conduction Velocity Primates
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