The 4 stages of the rodent’s female cycle are:
Metestrous – M
Diestrous -D
Proestrous -P
Estrous – E
Transitional stages, i.e. showing characteristics of two consecutive stages e.g. M-D or D-P, are not uncommon, particularly if smears are taken very early or late in the day.
The most commonly used smearing techniques (methods of obtaining vaginal cell samples) are:
a) Lavage or washing with saline or water from a pipette.
b) Swab or cotton bud (moistened with saline or water).
The standard swabbing method consists of inserting a moistened cotton bud swab into vagina, gently removing the cells from the vaginal lumen and walls and transferring the cells to a glass slide. It is the quickest method of smearing and the smears retain their original appearance indefinitely. However, because there is a risk of causing pseudopregnancy if the cervix is stimulated during estrus, we collect samples without inserting the cotton swab into the vagina.