家兔脊髓背半部下行痛抑制通路递质作用的分析

在21只麻痹而清醒的健康家兔观察到21个束旁核单位的痛敏放电,在刺激分离的脊髓背半部外周端后均被明显抑制。静注赛庚啶后有8个单位(占38.1％)的脊髓刺激效应被明显削弱;另外13个(占61.9)则基本不受影响。在5个不受赛庚啶影响的单位,其脊髓刺激效应全部可被纳络酮阻断;但在6个赛庚啶有阻断作用的单位,其脊髓刺激效应大多数(5/6)不被纳络酮阻断。结果提示,在脊髓下行纤维所实现的抑制过程中,一部分纤维通过内源性阿片的释放实现其效应,另一部分纤维则以5-HT为中间环节起作用。

Further Analysis of Neurotransmitters Involved in Antnoiciceptive Action Produced by Descending Fibers in Dorsal Half of Spinal Cord

Nociceptive discharges of 21 parafascicular (Pf) neurons were recorded ex-tracellularly on immoblized rabbits and discharges of all these neurons could be inhibited markedly, ranging from 54.3% up to 100%, by stimulation of caudal stump of the cut dorsal half of the spinal cord. After administration of cypro-heptadine (Cp) (1.0-3.0 mg/kg), the antinociceptive action of spinal stimulation in 8 out of 21 Pf neurons tested were obviously attenuated (disinhibitory rate 70.6%) while the remaining 13 neurons were not affected by this agent. In 5 neurons, which were not influenced by Cp, naloxone (Nx) admmstration (0.6-0.8 mg/kg) could block the effect of opinal stimulation (disinhibitory rate 66.9%). In 6 neurons, which had been influenced by Cp, NX administration did not block the effect of spinal stimulation in 5 of them. These results further confirm our hypothesis proposed earlier that endopioids act in series with noradrenalin in the antinociceptivc action produced by the descending fibers in the dorsal spinal cord while they might have little, if any, to do with the serotonergic system in this action.