Neurophysiologic and Histologic Changes Following Injection of Morphine , Meperidine and Pentazocine on Sciatic Nerve of Rabbits

Cheun, Jae Kyu; Song, Sun Ok; Kim, Jin Mo

Abstract

Intraspinal(intrathecal, epidural) narcotics administration had been widely used and well estabilished for pain control. The action mechanism of intraspinal narcotics has been well defined, and meperidine and pentazocine have been reported to be used as a sole agent for spinal anesthesia. The authors have already reported good loeal anestheticlike effets of meperidine and pentazocine clinically in patients scheduled for various surgeries, followed by experimen- tal evaluation of toxic effects of two drugs on the sciatic nerve of rats and dogs. This investigation was primarily undertaken to examine the difference in neurophysiological action between meperidine and morphine and also to evaluate early histological changes on aciatic nerve of rabbits within one week after injection of the each narcotics. Adult Korean rabbits were chosen as experimental animals because it is easy to observe neurophysiological activity with responses and to avoid of manipulating trauma. The rabbits were anesthetized using ketamine 10 mg/kg intramuscularly. The sciatic nerve of the rabbits was exposed and stimulated by a nerve stimulator to observe myoneural response as a control and then injected with 0.1% morphine 0.2 mg(Group I), 0.5% meperidine 10 mg(Group 2) and 0.3 % pentazocine 6 mg(Group 3). The sciatic nerve was stimulated for 20 minutes at 5 minutes interval and gait changes were carefully observed in the recovery room to see the myoneural activity, A specimen was taken at 4 and 24 hours, and 1 week after injection. The results were as follows, When the sciatic nerve was stimulated by a nerve stimulator, the normal muscle twitch was observed clearly in Group I with the morphine injection. However, in Group 2 with meperidine and Group 3 with pentazocine injection, muscle twitching decreased gradually and finally disappeared about after 10 minutes, Complete motor paralysis ceased after 60 minutes and muscle reaction returned to normal about 90 minutes after injection, Therafter, myoneural complications were not noticed in the 3 groups for a period of I week. All specimens of the 3 groups were inyestigated under light and with electron microscopic examination and they revealed mild vacuolziations scattered in axons of myelinated and unmyelinated nerves of some of the specimens but these were not significant. As a result of this investigation, we concluded that neurophysiologically, meperidine and pentazocine have local anesthetic-like effect, such as motor paralysis, but not with morphine, and neurohistologically, the above three norcotics have no significant toxic effects on nervous tissues.