Abstract
The effects of several anesthetics on spinal cord nociceptive neural mechanisms and their interactions with naloxone were studied in acute spinal cord transected cats. Intraarterial injection of bradykinin was used to stimulate chemical nociceptors. Spontaneous activity and the bradykinin-induced responses were recorded by the multiunit activity technique in the lateral funiculus. Thiamylal, nitrous oxide, halothane and diethylether suppressed the bradykinin-induced response considerably, but it was not antagonized by naloxone, 0.1–2.0 mg/kg iv. Enflurane had little effect on the bradykinin-induced response. The effects of these anesthetics on the spontaneous activity was divergent: nitrous oxide enhanced while the other anesthetics suppressed it to various degrees. Fentanyl, 30 μg/kg iv, suppressed both the bradykinin-induced response and the spontaneous firing. These effects were antagonized completely by naloxone, 0.1 mg/kg iv. All these findings indicate that anesthetics, except enflurane, suppress nociceptive neural mechanisms in the spinal cord and that their actions are not exerted through the opioid receptor-endorphin system.
Published Version
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