Genetic differences in progestin sensitivity in CD-1 and SW female mice

The lordotic behavior of ovariectomized CD1 and SW female mice was tested in response to estradiol benzoate(EB)+progesterone (P) or EB + 5 alpha-dihydroprogesterone (DHP) to determine (i) the role of progestin metabolism in the regulation of sexually receptive behavior, and (ii) strain differences in sensitivity to these progestins. A greater proportion of SW females resisted mounting attempts than CD-1 females, regardless of the progestin administered. However, the differences in mounting were not correlated with the expression of lordotic behavior. A greater proportion of SW females exhibited sexually receptive behavior when given EB+P in comparison to the CD-1 females. There were no genotypic differences in lordotic behavior in response to EB+DHP. The potential mechanisms mediating genotype-based differences in responsiveness are discussed, and the relationship of this report to previously described strain differences in progestin sensitivity are considered.