Neurophysiologic - Histological Changes Following Injection of Morphine , Meperidine , Pentazocine on Sciatic Nerve of Dogs

Cheun, Jae Kyu; Kim, Jin Mo; Chung, Chai Hong

Abstract

The authors have already reported good local anesthetic effects of meperidine and pentazocine clinically in patients scheduled for various surgeries, followed by experimental evaluation of toxic effects of two drugs on the sciatic nerve of rats. Intraspinal (spinal, epidural) morphine as well as other narcotics administration has been widely used and well established 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. We assurned that the action mechanism of subarachoid meperidine or pentazocine might be different to some extent from that of morphine. This investigation was primarily undertaken to examine the difference in action between meperidine and morphine and also to evaluate neurotoxic effects on sciatic nerve of dogs. Adult Korean dogs were chosen as exoerunebtak abunaks because it is easy to observe physiologic activity with responses and to avoid of manipulating trauma. The dogs were intubated and anesthetised with halothane and nitrous oxide. The sciatic nerve of the dogs was exposed and stimulated by a nerve stimulator to observe myoneural response and then injectied with 1% morphine 0.5 mg (Group 1), 5% meperidine 25 mg (Group 2) and 3% pentazocine 15 mg (Group 3). The dog was carefully observed in recovery room to see the myoneural activity After 1 week, 1 month or 2 months of careful observation, a specimen was taken under reanesthesia at 1 week, 1 month and 2 months after the careful obaervation, When the sciatic nerve was stimulated by a nerve stimulator, the normal muscle twitch was observed clearly in Group 1 with themorphine injection but was not observed in Group 2 with meperidine and Group 3 with pentazocine injection. Complete motor paralysis was noticed in Group 2 and 3 during the recovery period which lasted about 90 minutes, almost the same as the duration of drugs for spinal anesthesia, No complications were noticed in the 3 group during the periods of one week one month and two months. All specimens were examined and no abnormal findings were observed in the 3 groups. All specimens of the 3 groups were investigated under electrom microscopic examination and they revealed mild vacuolizations scattered in axon and ummyelinated nerves on the only some of the specimens and these were not significant. Severe nerve damage which was seen in the meperidine group of a preliminary experiment was not observed in this study. As a result of this investigation, we have not observed significant toxic effects microscopically or fuctioually.