How does estrus manifest in rats? - briefly
During estrus, female rats exhibit a swollen, pink vaginal opening, a marked lordosis posture when presented with a male, and a predominance of cornified epithelial cells in vaginal smears. These physiological and behavioral signs indicate the peak fertile phase.
How does estrus manifest in rats? - in detail
Estrus in rats is characterized by a series of physiological and behavioral changes that occur during the receptive phase of the estrous cycle. The cycle lasts approximately four to five days and includes proestrus, estrus, metestrus, and diestrus. Estrus itself typically spans 12–24 hours and can be identified by specific markers.
Physiological indicators:
- Swelling of the vulvar area, often visible as a slight enlargement and reddening of the vaginal opening.
- Increased vaginal epithelial cell cornification; cytological examination of vaginal smears shows a predominance of cornified, anucleated cells.
- Elevated serum luteinizing hormone (LH) and estradiol concentrations, measurable through blood sampling.
Behavioral manifestations:
- Heightened receptivity to male contact, demonstrated by lordosis posture when a male approaches.
- Increased locomotor activity, especially in the presence of a potential mate.
- Frequent lordosis quotient (the proportion of lordosis responses to male mounting attempts) approaching 1.0 during peak estrus.
Additional observations:
- Reduced aggression toward conspecific males, facilitating copulation.
- Shortened inter‑estrous interval if mating occurs, due to the luteal phase being bypassed.
Monitoring estrus in laboratory rats relies on a combination of vaginal cytology, visual inspection of genital swelling, and observation of lordosis behavior during male exposure. Accurate detection enables timed breeding, hormonal studies, and reproductive toxicology assessments.