Abstract
The brain dopaminergic system is involved in reward, movement, and goal-directed behaviors. The nucleus accumbens (NAc) receives converging corticolimbic inputs and mesolimbic dopamine inputs. There are 5 subtypes (D1-D5) in dopamine receptors. The specific role of each dopamine receptor subtype in the learning behavior and its neural correlates in the NAc has been known little, because of a paucity of specific drugs capable of discriminating each family member. However, recent advance in gene targeting technique allows us to address this problem. In the present study, we investigate the effects of dopamine D1 or D2 receptor knockout (D1R-KO or D2R-KO) in reward, locomotor activity and spatial learning. To test the neural correlates with these functions, we recorded NAc neural activity while the mouse performed spatial tasks. For behavioral performance, both D1R-KO and D2R-KO mice displayed reduced locomotor activity and slower acquisition of the spatial tasks. D1R-KO did, and D2R-KO did not, change the sensitivity to intracranial self-stimulation. For neural activity, D1R-KO and D2R-KO eliminated excitatory and inhibitory prereward responses, respectively, of NAc neurons. These results provide evidence for the specific role of D1R and D2R in NAc neural response to prediction of reward, locomotor activity and spatial learning. [Jpn J Physiol 54 Suppl:S188 (2004)]
