Hemispheric asymmetry in behavioral response to D₁ and D₂ receptor agonists in the nucleus accumbens

The present study examined the locomotor response of rats unilateral injections of the mixed D₁/D₂ agonist apomorphine, the D₂ agonist quinpirole, and the D₁ agonist SKF 38393 into the left or right nucleus accumbens (NA) of male Sprague-Dawley rats. There were 2 main findings. First, unilateral (left or right) injections of apomorphine, quinpirole, or SKF 38393 all provoked locomotor hyperactivity. The second and more important finding was that, at specific dosages, apomorphine and SKF 38393 injections into the right NA produced significantly more locomotor hyperactivity than identical injections into the left NA. These findings suggest the presence of asymmetries in the NA which may involve quantitative differences in the distribution of D₁ and D₂ receptors.