To elucidate the functional role of regulators of G-protein signaling (RGS) in vivo, it will be critical to (i) determine how RGS activity is altered in response to a variety of manipulations and (ii) observe how the system is changed when RGS protein function is altered genetically. To facilitate studies of dynamic regulation of RGS protein activity, this article describes detailed methods for radioisotopic in situ hybridization for semiquantitative analyses of RGS mRNA abundances. Toward characterizing the functional differences in mice with genetically altered RGS activities, this article describes a subset of behavioral tests suitable for assaying sensitivities to drugs of abuse. These protocols should provide valuable guidance for investigators to establish these methodologies independently in their own laboratories and, over time, increase our understanding of RGS function in vivo.