麻薬性鎮痛薬のネコ脊髄後角浅層侵害受容ニューロンに及ぼす直接効果

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The present studies were designed to examine the role of superficially located nociceptive neurons in spinal opiate analgesia. In the first study, we examined the influence of spinally administered fentanyl on the spontaneous and noxious heat-evoked activity of nociceptive specific (NS: n=14) and wide dynamic range (WDR: n=19) neurons in the superficial dorsal horn of decerebrate spinal cord transected cats. Both spontaneous and evoked activities of both types of neurons in the superficial layer were suppressed by spinally administered fentanyl. However, NS neurons were suppressed to a lesser degree than WDR neurons. In the second study, we also examined the influence of spinally administered morphine of 0.25 mg on spontaneous and noxious heat-evoked activity of WDR neurons (n=8) in the superficial dorsal horn of cats. Morphine reduced both spontaneous and evoked activities of WDR neurons. Comparing the results from both the superficially located WDR neurons (present study) and deeply located WDR neurons (previous study 18)), the rate of onset and the degree of suppression by morphine were similar. In the third study, we investigated the distribution and localization of intrathecally administered radioactive morphine in the cat spinal cord by light microscopic autoradiography, and compared the time course of penetration with the neurophysiologic results obtained in the second study. Silver grain numbers in the superficial dorsal horn were 2-3 times as large as that in the deep dorsal horn. These results demonstrate the difference in the sensitivity of NS and WDR neurons in the same superficial layer of the spinal cord to fentanyl suppression. It is suggested that there is a difference in sensitivity to morphine suppression between superficially and deeply located WDR neurons, or that deeply located WDR neurons are suppressed by morphine at the site of the superficial dorsal horn.
1989-08-01

麻薬性鎮痛薬のネコ脊髄後角浅層侵害受容ニューロンに及ぼす直接効果

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