Mechanism of spasmolytic action of piperidolate on isolated smooth muscle, particularly that of the uterine smooth muscle of the pregnant rat and the sex hormone pretreated rat

Abstract

Piperidolate blocked the contraction of ACh, Ba⁺⁺ and electrical stimulations on the isolated rat, mouse and guinea-pig ileum and trachea. In guinea-pig teania caeci, piperidolate like papaverine blocked specifically the tonic response, however, piperidolate in high doses completely blocked both spike and tonic responses. These results indicate that spasmolytic action of piperidolate like that of papaverine may depend upon inhibition of the release of store Ca⁺⁺. Moreover piperidolate, given at high doses, may inhibit the contractile elements in the smooth muscle. In the rat uterus pretreated with sex hormones, piperidolate nonspecifically blocked the contraction of ACh, Ba⁺⁺ and oxytocin and sex hormones had no influence on the spasmolytic action of piperidolate. The blocking action of papaverine to the contraction of Ba⁺⁺ and oxytocin in the dioestrus uterus was stronger than at any other stage of the hormonal cycle. In the pregnant rat uterus, however, the blocking action of piperidolate on the 20th ?? 22nd days of pregnancy was stronger than at other periods of gestation, while the blocking action of papaverine was much the same at any stage of pregnancy. These findings suggest that drug sensitivity as related to uterine motility may be dependent on different functional states of the uterus.