Hormones modulate many different facets of social behavior including social memory, affiliation, reward, and aggression. Pharmacological manipulations of these hormonal systems suggest that these actions occur via signaling in distinct brain regions. Further some effects organize behavior during a developmental sensitive period while others are modifiable in adulthood. Permanent germline genetic deletion cannot parse the temporal and/or region-specific functions of these genes. Thus we will develop post-mitotic genetic engineering tools to parse gene function within the context of specific brain regions or neuronal populations. We will use voles as a test species to 1) optimize viral delivery of constitutive and inducible S. pyogenesspCas9 (spCas9), and 2) determine the efficiency of genetic targeting in different brain regions and cell types.