Spike bursts in rabbit oviduct. II. Effects of estrogen and progesterone

Electrical activity of rabbit oviducts was recorded in vitro at 48 h after injection of human chorionic gonadotropin (HCG), 18 or 24 h after HCG with progesterone pretreatment, and 48 or 68 h after HCG with estrogen treatment 24 or 0 h after HCG, respectively. Frequency of spike bursts, pacemaker frequency, percentage of nonpropagating bursts, and probability of propagating in the uterine direction were obtained. Estrogen treatment decreased frequency of activity; at 48 h distance of propagation was increased and activity extended to 72.4% of the length of the oviduct compared to 65.7% in oviducts removed 48 h after HCG without estrogen. Only the ampullary-isthmic junction was active at 68 h after estrogen and HCG injection. Progesterone increased frequency and imposed a uterine bias, and activity extended to 73.6% of the length of the oviduct. These data support the hypothesis that properties of activity in the active area and the location of the active-inactive border regulate the location of ova in the isthmus of the rabbit oviduct.