Opioids have been used to allay anxiety and reduce pain associated with surgeny (Lowemstciu 1981). i1-tany of the opioids act via multiple opi¬oid receptors which could produce caning and opposing effects on A-ch induced contraction (Ranabedran 1985). The present study showed that morphine produce an inhibitory effect of muscle contraction of both direct and indirect responses. This inhibitory effect may he through a direct ac¬tion on opioid receptors, or inhibition of Ca" channels, or impairment of re-lease ofA ch from nerve ter-minaL;. Naloxon failed to antagonize the effect of morphine concluding that morphine action Ls not Through mu receptors |
