Psychomotor-activating effects mediated by dopamine D-2 and D-3 receptors in the nucleus accumbens

The contribution made by specific dopamine receptor subtypes to the inducti on of motor behaviors has not been firmly established. Here, we first chara cterized the behavioral effects induced by a D-2-class receptor agonist, br omocriptine, following injections into the nucleus accumbens (Acb). Bromocr iptine showed an atypical D-2-class receptor agonist profile, having no obs ervable effect on a range of motor behaviors. However, when coadministered with the D-1-class receptor agonist SKF 38393, bromocriptine showed a typic al D-2-class receptor agonist profile, enhancing locomotor activity and sup pressing spontaneous yawning. We then administered the dopamine receptor an tagonists L-741626 and nafadotride, which possess relative selectivity for D-2 and Dg receptors, respectively, prior to injections of dopamine agonist s into the Acb. Nafadotride significantly reduced the locomotor-enhancing e ffects elicited by the coadministration of SKF 38393 and the D-2-class rece ptor agonist (+)-PD 128907 into the Acb, and also attenuated the effects in duced by the combination of SKF 38393 and bromocriptine, although not signi ficantly so. L-741626 mildly attenuated the locomotor effects elicited by b oth drug combinations. Taken together, these results suggest that both D-2 and D-3 receptors in the Acb contribute to the expression of heightened psy chomotor activation. (C) 2000 Elsevier Science Inc. All rights reserved.