PARTIAL AGONISTIC ACTION OF MORPHINE IN THE RAT VAS DEFERENS

[摘要] References(12)Cited-By(3)Effects of morphine on the force of contraction of rat vas deferens were investigated. Morphine and β-endorphin decreased the electrically evolved tvvitch tension, in a close dependent manner. The inhibitory effect of morphine, however, was much weaker than that of β-endorphin. These effects of both morphine and β-endorphin were completely antagonized by naloxone. In the presence of 30 μM morphine, the dose-response curve of β-endorphin shifted to the right by about 10-fold. Moreover, morphine partly reversed the contraction depressed by 0.3 μM β-endorphin, in a dose dependent manner. These findings suggest that morphine acts as a partial agonist on the rat vas deferens. Marked tolerance to β-endorphin and change in the antagonist potency of morphine were not observed in the vas deferens isolated from morphine-dependent rats.

[学科分类] 药理学