刺激皮肤感受野对大鼠多觉型伤害性感受器诱发放电的影响

在大鼠尾部,重复压力刺激皮肤感受野,当间隔时间小于2min时,多觉型伤害性感受器的单位放电数随间隔时间的缩短而减少。压力与辐射热交叉刺激同一感受野,随后刺激的放电数也显著减少。皮下注射致痛剂引起持续性放电的背景上,分别向感受野施加按压、辐射热或电针刺激,随着放电增多后出现一个放电减少的过程。刺激支配尾部的交感神经则使减少的放电显著增多。结果表明,多觉型伤害性感受器受到刺激兴奋后有个感受性降低的过程。本文讨论了这一过程在按摩、针灸缓解痛机制中的可能作用。

INFLUENCE OF STIMULATION OF THE SKIN RECEPTIVE FIELD ON EVOKED DISCHARGES OF THE POLYMODAL NOCICEPTORS IN RATS

Unit discharges of polymodal nociceptors in the tail skin were elicited by mech-anical pressure, radiant heat and chemicals in anaesthetised rats. When repetitivepressure stimulation interval was 2 min or less, discharges evoked by the followingstimulations decreased markedly as compared with those evoked by the first stimula-tion. If a heat stimulation was interposed between two successive pressure stimula-tions, the discharges evoked by the pressure stimulations following the heat stimula-tion decreased obviously. The sustained discharges induced by chemicals were markedly decreased forminutes after application of pressure and heat stimulation or electrical acupunctureto the receptive field of the tail skin. During thes time, stimulation of the sympa-thetic nerve innervating the tail obviously increased the discharges. The results indicate that the sensitivity of polymodal nociceptors can be sup-pressed following an excitatory period evoked by local stimulation. The regionalpain relieving effect of acupuncture and massotherapy may be partly due to sup-pressed sensitivity of nociceptors.