吗啡抑制大鼠多觉型伤害性感受器持续放电

作利用复合致痛剂引起大鼠尾部皮肤多觉型伤害性感受器（ＰＭＮ）持续性放电模型，经股静脉注入吗啡（４ｍｇ／ｋｇ），显抑制ＰＭＮ持续性放电。吗啡抑制ＰＭＮ放电５０％的潜伏期为１０±４．５ｍｉｎ，抑制时程超过３０ｍｉｎ。纳络酮１ｍｇ／ｍｇ ｉｖ，可翻转吗啡的抑制作用。在慢性吗啡耐受大鼠，吗啡几乎失去其抑制作用。吗啡引起的ＰＭＮ放电数变化不呈一致关系。小剂量吗啡（１ｍｇ／ｋｇ）注入支配感受野皮肢的尾动脉

Inhibitory effect of morphine on sustained discharges of polymodal nociceptors in rats

To study morphine analgesic effect in periphery, the sustained discharges from a single polymodal nociceptor(PMN)induced by injecting a compound algogenic substances into the receptive field of the tail skin were recorded in anesthetized rats. Systemic administration of morphine inhibited significantly the dis-charges of PMN for more than 30 min. The inhibitory effect of morphine could be reversed by iv of l mg/kg naloxone;The effect of morphine could also be attenuated in rats which had been rendered tolerance to mor-phine.The changes of PMN discharges induced by morphine did not relate to blood pressure monitored in the carotid.The discharges of PMN could be significantly inhibited by 1 mg/kg morphine injected relatively local-ly, but not systemically. The results suggest that the analgesic effect of morphine is achieved,at least in part,by its peripheral action of suppressing the sustained discharges of PMN.