There are also a variety of different forms: Polyestrous Animals - Estrous cycles throughout the year (cattle, pigs, mice, rats). The efficiency of producing timed pregnant or pseudopregnant mice can be increased by identifying those in proestrus or estrus. The reproductive period and estrous cycle of mice commences about the 26th day after birth with the opening of the vagina, which is about 10 days before vaginal cornification . Evaluation of the female reproductive system is an important part of basic reproductive biology research, toxicology testing, and mutant mouse phenotype assessment. The estrous cycle in mice lasts for 4-5 days and is classified as proestrus, estrus, metestrus, and diestrus. Female rodents are poliestric, present spontaneous ovulation and show regular and successive estrous cycles that may vary with age and species. The female reproductive system is dynamic and the onset of puberty and the normal changes observed during estrous cyclicity can create challenges for an investigator. Estrous Cycle Interruption: Pheromones • S. Van der Lee and L.M. Boot, 1955 • Group housed females isolated from male mice tend to cease cycling • Females enter anestrus Whitten Effect • Wesley K. Whitten, 1956 • Pheromones in male urine induce estrus in females • used to synchronize estrus in females Photo:!Memorial!University!of! Keywords: estrous cycle, morphometric analysis, rat, Shorr method, vaginal smear. The estrous cycle has four phases, namely proestrus, estrus, metestrus and diestrus and lasts for 4 to 5 days (Table 1). Journal of the Korean Physical Society, Vol. Despite having overall shorter estrous cycles, mice with EAE had significantly longer (P < 6.48 × 10 − 10) mean proestrus–estrus follicular phases of the estrous cycle compared to disease-free control mice immunized with CFA alone. 4, October 2009, pp. 55, No. the estrous cycle of the rat (Long and Evans, 1922). Also do not confuse with "estrus", which is a phase of the cycle. is a platform for academics to share research papers. Since then, the evaluation of such changes in epithelial cell structure in These cycles are also influenced by light, seasons of the Visual observation of the vagina is the quickest method, requires no special equipment, and is best used when only proestrus or estrus stages need to be identified. In the 1920s, the approach was also used by Allen and Doisy (1923) in ovariectomized mice for an early uterotrophic assay to assess the vaginal response following the administration of estrogenic hormones. Background: Determination of the phases of the estrous cycle and induction of estrus (heat) in experimental animals remains useful, especially in reproductive function research. the estrous cycle were obtained following these steps: 1. a preliminary observation was made about the stage of the estrous cycle by assessing the vaginal opening of each mouse, 2. the stage of the estrous cycle was verified by vaginal cytology, 3. stage of estrous cycle was confirmed by mating mice … Introduction . The estrous cycle (British spelling, oestrous) is the main reproductive cycle of other species females of non-primate vertebrates, for example rats, mice, horses, pig have this form of reproductive cycle. Main body of the abstract: This review provides a detailed description and discusses extensively the variations observed in different phases of the estrous cycle in laboratory animals using rats and mice as examples.