Laboratory Rat Vaginal Cytology: A Quick Method of Staging Unstained Cells.

Background The estrous cycle in female laboratory rats is a critical parameter in reproductive and toxicological research, traditionally assessed through stained vaginal cytology. However, staining procedures can be time-consuming, costly, and less feasible in resource-limited settings. This study evaluates the efficacy of unstained vaginal cytology as a rapid, economical alternative for staging the estrous cycle in female albino Wistar rats. Methods Vaginal smears were collected daily from 30-day-old female albino Wistar rats for 15 consecutive days using saline lavage. Unstained smears were examined under light microscopy to identify the predominant cell types - cornified epithelial cells, nucleated epithelial cells, and leukocytes - and to classify the estrous phases (proestrus, estrus, metestrus, diestrus). Results Distinct cytological profiles corresponding to each estrous phase were reliably observed without staining. Proestrus featured predominantly nucleated epithelial cells, estrus was marked by abundant cornified epithelial cells, metestrus showed increased leukocytes, and diestrus was characterized by a predominance of leukocytes with fewer epithelial cells. The average cycle duration was four to five days. The unstained method provided clear, rapid identification of cycle phases comparable to traditional stained techniques. Conclusion Unstained vaginal cytology offers a simple, cost-effective, and reliable method for estrous cycle staging in female albino Wistar rats. This approach is particularly suitable for laboratories with limited resources, facilitating reproductive and toxicological research without compromising accuracy.