The action of reserpine and α-methyl-m-tyrosine on the analgesic effect of morphine in rats and mice

Abstract

Abstract The actions of α-methyl-m-tyrosine (mmt) and reserpine upon the analgesic effect of morphine has been studied in rats and mice. In rats, reserpine antagonised the effect of morphine, while mmt did not cause any appreciable change of the effect of morphine, injected either 2 or 24 hr after mmt. Reserpine also produced its antagonistic action to morphine in rats which were previously (24 hr) treated with mmt. Both mmt and reserpine potentiated the effect of morphine in rats pretreated (24 hr previously) with iproniazid. In mice, both mmt and reserpine antagonised the effect of morphine. Reserpine failed to do so in mmt pretreated animals. The effect of morphine was restored 24 hr after the injection of mmt. It is suggested that the inhibitory action of reserpine upon the analgesic effect of morphine is due to the antagonistic action of brain 5-ht, which is activated after being released from its stores by reserpine. The pattern of reserpine—mmt—morphine interactions in rats probably differs from that in mice.