Ovum Promotes Its Own Transport in the Oviduct of the Japanese Quail

Abstract

The mechanism of ovum transport was studied in 22 oviducts of the Japanese quail, by recording electric activity of the oviduct wall using six flexible suction electrodes in vitro. Regions of the oviduct in front of the ovum are quiescent. As the ovum progresses through the oviduct it causes excitation of the smooth musculature. Frequency of spike discharges increases with increasing circumference, declines at the maximal distension in the magnum and isthmus and increases again in the rear of the ovum, where frequency reaches its maximum. Frequency remains high in segments through which the ovum has progressed. In the magnum-isthmus junction the decrease of frequency of spike discharges at the maximal distension is less marked. Ovum transport is caused by a higher frequency of electric activity in the back than in the front of the ovum. It is suggested that distension caused by the ovum initiates a positive feed-back cycle in which the delay between the beginning of stretch and the resultant increase in activity to a maximum, together with the steepness of the frequency gradient, determines the rate of transport.