What is estrus in rats? - briefly
Estrus in rats denotes the short phase of the reproductive cycle when a female becomes sexually receptive, triggered by an estrogen peak that leads to ovulation. This stage recurs every four to five days and lasts only a few hours.
What is estrus in rats? - in detail
Estrus in female rats refers to the period of sexual receptivity within the estrous cycle when the animal is capable of conceiving. The cycle lasts approximately four to five days and consists of four distinct stages: proestrus, estrus, metestrus, and diestrus. Hormonal fluctuations drive these phases; rising estradiol levels during proestrus trigger the luteinizing hormone surge that initiates estrus, after which progesterone dominates during metestrus and diestrus.
During estrus, rats exhibit characteristic behaviors such as increased locomotion, lordosis when approached by a male, and a marked reduction in aggression toward conspecifics. Vaginal cytology provides a reliable method for stage determination: a predominance of cornified epithelial cells indicates estrus, while a mixture of leukocytes and nucleated epithelial cells signals metestrus, and a predominance of leukocytes denotes diestrus. The transition from proestrus to estrus typically occurs within 12–14 hours after the luteinizing hormone peak.
Timing of estrus is synchronized with the animal’s circadian rhythm; peak receptivity generally appears during the early dark phase. Environmental cues, such as light-dark cycles and pheromonal signals from males, can modulate cycle regularity. In laboratory settings, researchers often use the Whitten effect—exposure of a group of females to a male—to induce estrus synchrony and reduce variability.
Understanding the estrous phase is essential for experimental design involving reproductive physiology, toxicology, or behavioral studies. Accurate staging ensures appropriate mating schedules, improves interpretation of hormone assays, and minimizes confounding factors related to hormonal status.