EFFECT OF Ca ++ CHANNEL BLOCKERS AND H2 RECEPTOR BLOCKERS ON MODULATION OF PAIN THRESHOLD AND ANALGESIC ACTIVITY OF MORPHINE IN RATS
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This work was carried out on 42 albino rats to study the effect of the C.C.B ( verapamil ) and H2 receptor antagonist ( ranitidine ) on modulation of pain threshold and morphine an.tinocicept tiue action. Our study demonstrated that C.C.B (verapamil) has antinociceptive action to thermal stimulation indicating that Ca + is an important mediator in pain pathway. However pretreatment of rats with a single Intraperitoneal dose (LP) of C.C.B neither _p otentiates nor inhibited the analgesic activity of morphine. On the other hand C.C.B (veraparnil) decreased the antinociceptive action of morphine when it was given in a single (LP) dose after morphine injection. The H2 receptor antagonist (rantidirte) induced antinociceptive activity which may be through its binding to opiate receptors as the opiate antagonist naloxone blocked this effect. Pretreatment of rats with rartitidine greatly potentiated the analgesic activity of morphine, a result which may be of value in reducing the dose of morphine and hence its side effects.