D3 dopamine receptor-deficient mouse: evidence for reduced anxiety.

Mice without functional D3 dopamine receptors were examined in two animal models for anxiety: the open-field test and the elevated plus-maze test. In the open field, D3 receptor-deficient mice (D3-/-) entered the center significantly more often than normal (D3+/+) littermates, suggesting an anxiolytic-like effect of the D3 receptor mutation. Consistent with this finding, D3-/- mice entered open arms of the plus maze significantly more often and longer than D3+/+ littermates, but did not differ in closed-arm entries, an index of general activity. Heterozygous (D3 +/-) animals showed intermediate behavioral changes. We interpret these results as indicative of reduced anxiety in mice without D3 receptors. Our findings thus suggest that D3 dopamine receptors are involved in the regulation of anxiety.