Determining the Stage of the Estrous Cycle in Female Mice by Vaginal Smear

Female mice undergo a 3- to 5-d, hormonally controlled estrous cycle. The estrous cycle is divided into different stages, including diestrus, proestrus, estrus, and metestrus. These stages can easily be determined by examining washes or cell smears of the vagina. Determining the stage of the estrous cycle may be important for setting up matings, identifying receptive females for artificial insemination, and analyzing phenotypes of the female reproductive tract.