The Luteal Phase Is Modified by Copulation in Some Species

In rodent species the luteal phase of the ovarian cycle is extended by copulation. The life span of CL is only 1 to 2 days in the absence of copulation. Copulation initiates the release of prolactin, which results in prolongation of luteal activity for up to IO or 11 days in the absence of pregnancy. This phenomenon is often called pseudopregnancy. In the canine, spontaneous regression of the CL marking the end of diestrus occurs in association with increased levels of prolactin, causing clinical pseudopregnancy. Nonpregnant bitches can nest, lactate, and nurture objects during this time.