Responses of Cutaneous A-Fiber Nociceptors to Noxious Cold. Simone, Donald A. and Keith C. Kajander. Departments of Psychiatry, Oral Science, and Cell Biology and Neuroanatomy, and Graduate Program in Neuroscience.
APStracts 3:0251N, 1996.
Responses of cutaneous nociceptors to natural stimuli, particularly mechanical and heat stimuli, have been well documented. Although nociceptors are excited by noxious cold stimuli, there have been few studies of their stimulus- response functions for cold stimuli over a wide range of stimulus temperatures. Furthermore, the proportion of nociceptors excited by noxious cold is not clear. In the present study, we examined responses of mechanosensitive A nociceptors and low threshold mechanoreceptors to a wide range of cold stimuli that included stimulus temperatures below 0 C. Electrophysiological recordings were made from single primary afferent fibers in the saphenous nerve of anesthetized rats. Cutaneous sensory receptors were classed according to their conduction velocity and subgrouped functionally according to their responses evoked by mechanical, heat and cold stimuli (0 C). Responses evoked by a wide range of cold stimulus intensities that included stimuli considered innocuous and noxious (painful) were then assessed. Stimuli of 20 C to -20 C were delivered to the receptive field via a 1 cm2 contact thermode from a base temperature of 32 C. Stimuli were applied in descending order of 2 decrements. Stimulus ramp rate was 5 C/s, and stimulus temperatures were applied for a duration of 10 s.

Received 17 September 1996; accepted in final form 12 September 1996.
APS Manuscript Number J748-6.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 31 December 1996