Opioids have been used to calturi nnxtety and reduce pain associated with surges) (Lowernstcin 1981). Many of the opioids act via multiple opi¬oid receptors which could produce varying and opposing effects on A-ch induced contraction (Ranahedran 1985). The present study showed that morphine produce an inhibilonj effect of muscle contraction of both direct and indirect responses. This uihibiton; effect may he through a direct ac¬tion on op fold receptors- or inhibition of Ca" chann eLs, or impairment of re-lease nJ A ch from nerve terminals. Naloxon /ailed to antagonize the effect of morphine concluding that ;morphine action is not through mu receptors.