ラットにおいてモルヒネにより誘発される筋強直の筋電図法による定量的評価およびそれに対する薬物の作用

抄録

In order to examine drug effects on an extrapyramidal symptom the muscular rigidity produced by morphine was evaluated by an electromyographic method in the gastrocnemius muscle of rats and the result was compared with that by a catalepsy method. Morphine hydrochloride at a dose of 2.5 mg/kg s.c. produced a significant increase in electromyogram activity. An administration of morphine hydrochloride at doses of 10, 20 and 40μg into the spinal subarachnoidal space or cerebral ventricle also produced a marked increase in electromyogram activity. These effects of morphine were antagonized by naloxone permoate at doses of 0.5 to 2 mg/kg i.p. When morphine rigidity was estimated by the catalepsy method, the identification limit of the dose was more than 5 mg/kg s.c. The increase in electromyogram activity after morphine hydrochloride 2.5 mg/kg s.c. was suppressed by centrally-acting muscle relaxants, mephenesin, baclofen and carisoprodol. It was also inhibited significantly by dopaminergic agonists, apomorphine and L-dopa. These results suggest that an electromyographic analysis in the gastrocnemius muscle of lightly-restrained unanesthetized rats is a sensitive method to detect quantitatively the rigidity produced by morphine and to evaluate drug effects on it.