Vomeronasal phenotype and behavioral alterations in Gαi2 mutant mice

Several social and reproductive behaviors are under the influence of the vomeronasal (VN) organ; VN neurons detect odorous molecules emitted by individuals of the same species [1, 2]. There are two types of VN neurons, and these differ in their expression of chemosensory receptors and G protein subunits. The significance of this dichotomy is largely unknown. VN neurons express high levels of either Galphai2 or Galphao. A mouse line carrying a targeted disruption of the Gai2 gene [3] offered the opportunity for studying the effects of a lack of receptor signaling through the heterotrimeric Gi2 protein in one VN cell type. As a consequence of this deficiency, the number of VN neurons that normally express Gai2 is decreased by half. These residual neurons are defective in eliciting a response in their target neurons in the accessory olfactory bulb. Moreover, Galphai2 mutant mice show alterations in behaviors for which an intact VN organ is known to be important. Display of maternal aggressive behavior is severely blunted, and male mice show significantly less aggression toward an intruder. However, male mice show unaltered sexual-partner preference. This suggests that the two types of VN neurons may have separate functions in mediating behavioral changes in response to chemosensory information.