Responses of cutaneous A-fiber nociceptors to noxious cold.
Responses of cutaneous A-fiber nociceptors to noxious cold.
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DOI：
10.1152/jn.1997.77.4.2049
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发表时间：
1997-04
影响因子：
2.5
通讯作者：
Donald A. Simone;K. Kajander
中科院分区：
文献类型：
--
作者：
Donald A. Simone;K. Kajander
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 delta-nociceptors and low-threshold mechanoreceptors to a wide range of cold stimuli that included stimulus temperatures 30 m/s). These were subgrouped according to their adaptive properties as slowly or rapidly adapting, and according to whether they were excited by hair movement (hair follicle afferent fibers). All nociceptors were excited by noxious cold. Only 30% of nociceptors were considered sensitive to cold on initial classification with the use of a cold stimulus of 0 degrees C. However, all nociceptors were excited by stimulus intensities <0 degreesC. Response thresholds for cold ranged from 14 to -18 degrees C (-4.6 +/- 1.07 degrees C, mean +/- SE). The total number of impulses, discharge rate, and peak discharge increased monotonically as intensity of cold stimuli increased. Power functions were used to determine the rate at which the number of impulses increased as stimulus intensity increased. The slopes of power funcions ranged from 0.12 to 2.28 (mean 1.07 +/- 0.13). Most mechanoreceptors were not excited by cold stimuli. The only types of mechanoreceptors that responded reliably to cold stimuli were the slowly adapting mechanoreceptors. Responses usually occurred during the temperature ramp when the skin temperature was decreasing. There was no evidence that mechanoreceptors encoded the intensity of cold stimuli at intensities above or below 0 degrees C, because evoked responses did not increase with intensity of cold stimuli. It is concluded that the proportion of cutaneous A delta-nociceptors excited by noxious cold stimuli has been underestimated in previous studies. All nociceptors were excited by stimulus temperatures <0 degrees C and encoded the intensity of cold stimuli. It is therefore likely that cutaneous A delta-nociceptors contribute to the sensation of cold pain, particularly pain produced by stimulus temperatures <0 degrees C.
