Cyclic Variations in Intraluminal Pressure in the Isthmus of the Oviduct in Unrestrained Gilts

Cyclic variations in intraluminal pressure in the isthmus of the oviduct in unrestrained gilts were observed. During proestrus and through the first day of oestrus, base pressure and total pressure increased reaching a high pressure on the second half of day 1 (first day of standing oestrus) after which a decrease was seen with a low base pressure recorded on the second half of day 3 and a low total pressure appearing on the second half of day 3 lasting through day 4. The frequency of the phasic pressure fluctuations in the isthmus also increased during proestrus and reached a high value on the first half of day 2. The frequency then declined to a low value on day 4. The pattern in which the phasic pressure fluctuations were arranged changed from predominantly wavy during proestrus and through the first half of day 2 to progressively more irregular in appearance after day 2. Outbursts of increased intraluminal pressure with varying propagation directions occurred with a fairly high frequency from the second half of day 2 and through day 3.