Male and female genotype mediate pheromonal regulation of the mouse estrous cycle

Estrous cyclicity was studied to examine the possibility that strain differences in the regularity of the mouse estrous cycle are the result of different olfactory signals produced by the male. Females with regular estrous cycles (lines E and S1) were housed in the olfactory presence of males from a line with irregular cycles (line CN-) or in the presence of males of their own line (used as a control). Females with irregular cycles (line CN-) were housed in the presence of males from a line with regular cycles (line E) or were exposed to males of their own line. The regularity of the estrous cycle decreased in line E females (regular cycles) when exposed to line CN- males (irregular cycles). The decreased regularity of line E cyclicity resulted from an increased period of diestrus, i.e., lengthening of the cycle. In contrast, line S1 females (regular cycles) did not show any change in estrous cyclicity when exposed to line CN- males. The period of diestrus increased in line CN- females when they were exposed to line E males. These results provide evidence that 1) the genotype of the male can influence the regularity of the estrous cycle, and 2) the genotype of the female regulates her responsiveness to environmental factors (e.g., male odor).