Action of Cytochalasin B on the Contraction of Smooth Muscle of Guinea Pig Taenia Coli, Vas Deferens and Rat Uterus

Effect of cytochalasin B (CB) on in vitro contractile response of smooth muscle preparations of guinea pig taenia coli, vas deferens and estrogen treated rat uterus were investigated. In all these preparations, CB (1 to 10 μg/ml) caused prompt, significant and reversible inhibition of contraction. Tetrodotoxin (TTX) was used to block the intramural nerve activity of these preparations. In the presence of TTX, CB still inhibited the contraction of taenia coli and uterine strip, but it (10 to 50 μg/ml) did not inhibit the direct muscular contraction of vas deferens. It was concluded from these results that in taenia coli and in myometrium, CB acts directly on smooth muscle cells and inhibits contraction, but in vas deferens, inhibitory effect of CB is almost entirely exerted through the inhibition of neural transmitter release from hypogastric nerve endings in this tissue.