Comparative Medicine Program, University of Missouri, Columbia, Missouri; Department of Veterinary Pathobiology, University of Missouri, Columbia, Missouri.
Veterinary Research Scholars Program, University of Missouri, Columbia, Missouri.
J Am Assoc Lab Anim Sci. 2020 May 1;59(3):282-287. doi: 10.30802/AALAS-JAALAS-19-000112. Epub 2020 Apr 2.
Vaginal cytology is the most common method of monitoring the estrous cycle in rats; however, this test requires specific technical training and can be subject to interpretation. Vaginal impedance offers a quicker and less technically challenging alternative and has been used successfully to identify estrus in normally cycling breeder rats. We hypothesize that vaginal impedance can also be used to stage the estrous cycle in rats that have been given luteinizing hormone releasing hormone (LHRH) for timed mating. Vaginal impedance measurements and vaginal cytology were performed in LHRH-primed female rats ( = 36) at the expected peak of proestrus and paired with proven stud males. Breeding success was determined by gross necropsy to detect embryo implantation sites in the female rats. We found that the predictive rates of vaginal cytology and impedance measurement for proestrus were similar; however, both methods resulted in high proportions of false positive and false negative determinations (28% and 31%, respectively). We further hypothesized that females respond to LHRH at variable rates, resulting in variable times of peak proestrus. To test this, vaginal impedance measurements were performed multiple times throughout the expected day of proestrus in LHRH-primed female rats ( = 36). Females were either paired with a male 24 h after reaching the proestrus threshold ( = 18) or paired according to our standard protocol at 1300 h on the day after the expected proestrus ( = 18). Sequential measurements reduced false positive and negative rates (14% and 8%, respectively). Pregnancy rates did not differ based on the time of pairing during expected estrus. Overall, we determined vaginal impedance can be more successful than vaginal cytology at identifying proestrus in the rat, but only if multiple measurements are taken.
阴道细胞学是监测大鼠发情周期最常用的方法;然而，这种测试需要特定的技术培训，并且可能存在解释上的差异。阴道阻抗提供了一种更快、技术要求更低的替代方法，并已成功用于识别正常发情的繁殖大鼠的发情期。我们假设阴道阻抗也可用于对已给予促黄体激素释放激素 (LHRH) 进行定时交配的大鼠进行发情期分期。在预期发情前期高峰时，对接受 LHRH 刺激的雌性大鼠 (n = 36) 进行阴道阻抗测量和阴道细胞学检查，并与已证明的雄性大鼠配对。通过大体解剖检查雌性大鼠以检测胚胎植入部位来确定繁殖成功率。我们发现，阴道细胞学和阻抗测量预测发情前期的准确率相似;然而，这两种方法都导致了高比例的假阳性和假阴性结果(分别为 28%和 31%)。我们进一步假设，雌性对 LHRH 的反应速度不同，导致发情前期高峰的时间不同。为了验证这一点，我们对接受 LHRH 刺激的雌性大鼠 (n = 36) 在预期发情前期的整个期间多次进行阴道阻抗测量。在达到发情前期阈值后 24 小时 (n = 18)，或根据我们的标准方案在预期发情前期后的 1300 小时 (n = 18)，与雄性大鼠配对。连续测量降低了假阳性和假阴性的比例(分别为 14%和 8%)。根据预期发情期的配对时间，妊娠率没有差异。总体而言，我们确定阴道阻抗比阴道细胞学更能成功地识别大鼠的发情前期，但前提是要进行多次测量。
