Effect of ovulation on the response of the rabbit oviduct to acetylcholine in vitro.

Acetylcholine had a stimulatory effect on both the longitudinal and circular isthmi of the rabbit fallopian tube in vitro. The longitudinal isthmus was more responsive than the circular isthmus. The stimulatory effect was blocked by phentolamine (3 x 10(-7) M). The oviduct obtained from animals sacrificed 24 h after human chorionic gonadotropin (hCG) administration was more responsive to acetylcholine as compared to the oviduct obtained 72 h after hCG and from animals without ovulation induction. The maximum isometric tension developed was greater in tissues obtained from animals sacrificed 24 h after hCG. The results of this study suggest that the effect of acetylcholine may be partly mediated through the release of noradrenaline and may have a functional role in the regulation of ovum transport.