GRM2 and Anxiety: (2005) found a similar pattern of results for their GRM2−/− mice, with increased locomotor activity observed in a number of different testing situations (including the open field test, light/dark transition test, elevated plus maze, social interaction test), but no genotype differences in performance measures more directly related to anxiety (although note that we did not replicate these effects in GRM2−/− mice in the present study).