The sensitivity of the longitudinal and circular muscle layers of the rat's myometrium to oxytocin in vitro during pregnancy

To test the hypothesis that binding site regulation is the primary process controlling the responsiveness of the rat's myometrium to oxytocin during pregnancy, I have studied the effects of oxytocin on longitudinal and circular strips of myometrium in vitro throughout pregnancy. Longitudinal muscle was as sensitive on day 10 of pregnancy (EC50 = 1.6 nM) as it was at term (EC50 = 1.3 nM) and there was no significant change in the mean maximal …