Longitudinal contractions of the rabbit oviduct do not change in amplitude or rate at different intervals after mating to 4 days, but they become greater in pregnancy and less in pseudopregnancy. Oil and India ink are spread in both directions by segmentation and pendular movement of the smooth muscle but they are arrested at 2–3 cm anterior to the tubo-uterine junction unless more than 0.1 ml is used. Paralysis of the muscle with nicotine prevents movement. When a plastic tube is inserted through the tubo-uterine junction, passage of ova past the critical zone is hastened. Ligature of the infundibular end of the oviduct causes distension, so that oviduct secretions must normally pass through the infundibulum and not into the uterus. This probably aids the transport of spermatazoa while ova are kept from escaping in this direction by the cilia and by the mucosal folds.
A mechanism is present at the lower end of the rabbit oviduct which prevents the entry of ova into the uterus until the reproductive organs come under the influence of progesterone. In normal rabbits, distention of the oviduct caused by ligating the infundibular end, recedes between the 60th and 72nd hour post coitum. Estrogen injections prolong distention. Progesterone does not markedly speed up ovum transport and is effective only when it can overcome the effect of endogenous estrogen. Circular muscle activity was recorded at three levels of the oviduct. Activity in the ovarian end greatly exceeded that in the lower sections of the tube. At the uterine end activity was very slight or not present at all. Several attempts to demonstrate the presence of edema in the tubo-uterine junction were unsuccessful.
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