刺激交感神经对大鼠多觉型伤害性感受器诱发和自发放电的不同作用

多觉型伤害性感受器是皮肤内专一性较强的痛觉感受器。本实验用剥制神经细束的技术,引导大鼠尾神经C类纤维的传入放电反映多觉型伤害性感受器的活动,以判定刺激交感神经对外周痛觉感受过程的调制作用。测试了57个该类感受器的单位放电,发现下述两个主要事实:(1)刺激腰骶部交感干外周端,可以显著抑制伤害性刺激(包括机械压力,直流电-钾离子,热烫等)诱发的多觉型伤害性感受器的单位放电,其作用出现较快,可使放电数减少1/3左右,后作用延续十多分钟。局部动脉注射去甲肾上腺素也产生类似的抑制效应。从而证实交感神经具有抑制痛觉感受器的作用。(2)交感神经对部分多觉型伤害性感受器活动的调制具有双重作用的特点,即对同一单位因外加刺激引起的诱发放电有抑制作用,对其自发放电则有易化作用。讨论了交感神经这一双重作用的临床意义以及针刺通过交感神经调制外周痛觉感受过程的设想。

DIFFERENT EFFECTS OF SYMPATHETIC STIMULATION ON EVOKED AND SPONTANEOUS DISCHARGES OF THE POLYMODAL NOCICEPTORS IN RAT

In the present study the tail nerve in rat was dissected of small bundles offibers and unit discharges of afferent C fibers evoked by noxious stimuli such asmechanical pressure and direct current potassium iontophoresis and heat wererecorded. The unit discharges were used as indices of activity of the polymodalnociceptors, the specialized pain receptors in skin, to investigate the modulatingeffects of sympathetic nerve on peripheral sensation process of pain. 57 units ofthe polymodal nociceptors were studied, the following two main facts were found. (1) Stimulation of the peripheral end of the cat lumbosacral sympathetictrunk could inhibit markedly the unit discharges of the polymodal nociceptorsevoked by noxious stimuli. The inhibitory effect occurred quickly and caused the number of unit dischargesto decrease about one-third. The after effect lasted for more than ten min. In-jection of norepinepherine into the tail artery had a similar inhibitory effect. Thisfinding confirmed our previous report that the sympathetic nerve possessed an in-hibitory effect on pain receptors. (2) The modulating effect of sympathetic stimulation on the activity of partsof the polymodal nociceptors showed a dual nature, namely, it inhibited the evokeddischarges but facilitated the spontaneous discharges of the same unit. Based on these results, it was suggested that abnomality of the dual effect ofthe sympathetic nerve on the polymodal nociceptors might be one of the causesproducing causalgia and an assumption that acupuncture might modulate theperipheral sensation process of pain via the sympathetic nerve was discussed.