The effects of variations in length of suction pipette inserted during vaginal smear cytology procedure on estrous cycle in Sprague–Dawley rats

Abstract

Estrous cycle is a periodic reproductive sequence of events in most female laboratory animals that are used for basic research. Several methods have been used to stage estrous cycle, these include visual method, vagina smear cytology evaluation, chemical analysis of urine and the analysis of electrical resistance. The vaginal smear cytology (VSC) evaluation method is commonly used to stage estrous cycle because it is a faster method coupled with easy execution and not as expensive as the other methods. The study of estrous cycle is primary to all investigations in reproduction and related areas. For the generation of dependable research outcome from VSC evaluation method, the technique for the collection of vagina smear and its microscopic interpretation must be done according to established standards. Many reports in literature concerning VSC evaluation method, lack comprehensive demonstrations and uniformity which lead to loss of homogeneity and hence provide study outcomes that are not authentic.  Therefore, this present investigation was designed to establish the standard value of inserted length of suction pipette during smear extraction technique when using VSC method to study estrous cycle. A total of fifteen experimental animals were recruited for this investigation. The animals were subdivided into three groups 1 to 3. The lengths of pipette inserted into the vagina canal were varied from 1mm, 2mm to 4mm in group 1, 2 and 3 respectively. The outcome from this investigation showed that the depth of suction pipette inserted during smear extraction procedure in VSC method has effect on estrous cycling. Estrous cycle was maintained with 2mm insertion length with approximate four days cycle and phases changing daily.