Study: Loss of Smell in Females Elicits Male Behavior

Evidence that the Nose Really Knows Sex

A new study published online in the journal Nature, reveals that the loss of the sense of smell by female mice, resulted in the development of behavior that was distinctly male.

The study was conducted by Tali Kimchi, Jennings Xu, and Catherine Dulac of the Department of Molecular and Cellular Biology at Harvard University in Cambridge, Massachussets.

The study was seeking to gain further insight into the effects of Trpc2, an ion channel that is expressed by neurons of the vomeronasal organ (VNO). This structure in conjunction with the olfactory epithelium (cells that mediate smell), is critical in detecting pheromones, the chemical substances that help animals communicate with each other.

Previous studies, had shown that male mice that did not express the Trpc2 gene, had a limited capacity to recognize and distinguish the sex of other mice. Furthermore, they did not display the stereotypical aggressive tendencies against same-gender animals.

For this study, the research team specifically evaluated Trpc2-deficient female mice. What they found was that these animals exhibited a marked reduction in female-specific behavior. In particular, they did not display the characteristic maternal traits of protecting their young or a propensity for lactation.

Much to the astonishment of the research team, the female mice also exhibited tendencies that were quite androgenic. These behaviors included: mounting, pelvic thrust, solicitation, anogenital olfactory investigation, and complex ultrasonic vocalizations.

The report affirmed that this type of behavior was also observed in adult female mice that underwent surgical removal of the VNO. Interestingly, the absence of this structure did not affect the normal estrogen cycle of the animals or their natural hormone levels.

The research team concluded that pheromone detection via the VNO of normal female mice, serves to enhance female behavior and at the same time repress male demeanor. They also hypothesized that the neurological pathways that drive male behavior are intrinsically present and appear to be intact in the brains of female mice.