Repeated Collection of Vaginal Smear Causes Stress in Mice

Women are more likely to be misdiagnosed in many neuropsychiatric disorders than men. One of the possible underlying reasons for this disparity may be more frequent use of male mice than female mice in neuroscience studies. With the increasing realization of the shortcomings of this approach in understanding the neurobiological basis of these disorders, many funding agencies mandate the inclusion of both male and female subjects in study design. As the behaviors vary with the stage of the estrous cycle, the collection of vaginal smears to identify the estrous stage becomes a widely used procedure. Here we tested whether vaginal smear collection causes similar effects to that of stress by evaluating an increase in depression-like behavior and impairment in memory.

Vaginal smear was collected from Swiss albino mice twice a day for 10 days. In order to test depression-like behavior tail suspension, sucrose preference and splash tests were conducted. Novel object recognition and novel object location tests were performed 1 hour and 24 hours after training to evaluate short-and long-term memory respectively.

The female mice whose vaginal smears were collected demonstrated increased behavioral despair and anhedonia. Vaginal smear group showed deficits in both short-term and long-term memory when compared to the control group.

Our results indicate that the collection of vaginal smear not only increased depression-like behaviors in mice, but also impaired short-term and long-term memory, indicating that the procedure of vaginal smear collection was stressful. We recommend to consider other ways of estrous cycle staging when studying behavior.