Miaskowski C, Taiwo Y O, Levine J D
School of Nursing, University of California, San Francisco 94143.
Brain Res. 1990 May 7;515(1-2):323-5. doi: 10.1016/0006-8993(90)90616-j.
The intrathecal administration of the opiate antagonist naloxone produced a dose-dependent biphasic change in mechanical nociceptive threshold, in the rat hindpaw. Lower doses (50 pg to 500 ng) produced analgesia while higher doses (5 to 50 micrograms) resulted in successively less analgesia. In contrast, the intracerebroventricular administration of naloxone up to a dose of 5 micrograms (i.e. a dose 10,000 times greater than that required to produce a maximal analgesic effect) only produced analgesia. The ability to differentiate between the analgesic and pain-enhancing properties of naloxone by administration at different anatomical sites is compatible with the suggestion that the analgesic and pain-enhancing effects of naloxone are produced by separate mechanisms of action.
在大鼠后爪，鞘内注射阿片类拮抗剂纳洛酮会引起机械性伤害感受阈值呈剂量依赖性双相变化。较低剂量（50 pg至500 ng）产生镇痛作用，而较高剂量（5至50微克）则导致镇痛作用逐渐减弱。相比之下，脑室内注射高达5微克剂量的纳洛酮（即比产生最大镇痛效果所需剂量大10000倍的剂量）仅产生镇痛作用。通过在不同解剖部位给药来区分纳洛酮的镇痛和致痛特性，这与纳洛酮的镇痛和致痛作用是由不同作用机制产生的观点相符。
