Ferreira S H, Molina N, Vettore O
Prostaglandins. 1982 Jan;23(1):53-60. doi: 10.1016/0090-6980(82)90021-1.
Prostaglandin E2 injected in the rat paw causes hyperalgesia which is antagonized by local injections of opiate and opiate antagonists. In the present investigation in rats it is shown that naloxone has an analgesic effect at doses as low as 2 micrograms/site, injected into the rat hind paw. At a dose that has no analgesic effect (1 microgram/site) naloxone antagonized the analgesia produced by either local or systemic administration of morphine. Local administration of levorphanol (50 micrograms/site) caused a 50% reduction in the intensity of the hyperalgesia induced by prostaglandin E2. A dose four times greater of its isomer, dextrorphan, had little analgesic effect. The present results support the suggestion that this peripheral analgesia is the result of an action of opiates in receptors located at the nociceptors.
注射到大鼠爪部的前列腺素E2会引起痛觉过敏，而局部注射阿片类药物和阿片类拮抗剂可对抗这种痛觉过敏。在目前对大鼠的研究中发现，将纳洛酮以低至2微克/部位的剂量注射到大鼠后爪时具有镇痛作用。在无镇痛作用的剂量（1微克/部位）下，纳洛酮可对抗局部或全身给予吗啡所产生的镇痛作用。局部给予左啡诺（50微克/部位）可使前列腺素E2诱导的痛觉过敏强度降低50%。其异构体右啡烷剂量增大四倍几乎没有镇痛作用。目前的结果支持这样的观点，即这种外周镇痛是阿片类药物作用于位于伤害感受器的受体的结果。
