In mice, pheromone detection is mediated by the vomeronasal organ and the main olfactory epithelium. Male mice that are deficient for Trpc2, an ion channel specifically expressed in VNO neurons and essential for VNO sensory transduction, are impaired in sex discrimination and male–male aggression. We report here that Trpc2-/- female mice show a reduction in female-specific behaviour, including maternal aggression and lactating behaviour. Strikingly, mutant females display unique characteristics of male sexual and courtship behaviours such as mounting, pelvic thrust, solicitation, anogenital olfactory investigation, and emission of complex ultrasonic vocalizations towards male and female conspecific mice. The same behavioural phenotype is observed after VNO surgical removal in adult animals, and is not accompanied by disruption of the oestrous cycle and sex hormone levels. These findings suggest that VNO-mediated pheromone inputs act in wild-type females to repress male behaviour and activate female behaviours. Moreover, they imply that functional neuronal circuits underlying male-specific behaviours exist in the normal female mouse brain.There is some controversy over whether this result is unique to inbred laboratory mouse strains, so Dulac is now breeding wild mice with the Trpc2-mutant mice, to experiment with a 'wilder' version.
Tuesday, August 21, 2007
Male sexual behavior circuits in female brains...
A fascinating bit of work by Kimchi and Dulac shows that female mice missing a gene involved in pheromone detection show the same sexual behaviour as males. Their abstract: