Anatomical differentiation within the nucleus accumbens of the locomotor stimulatory actions of selective dopamine agonists and d-amphetamine

The effects of local injections of dopamine receptor agonists into various areas within the nucleus accumbens or the medial caudate-putamen on the generation of locomotor activity were examined. Combinations of 0.32 μg/side of the dopamine receptor agonists SKF 38393 (D₁) and quinpirole (D₂) produced increases in locomotor activity that varied according to the rostral-caudal placement of the cannulae within the nucleus accumbens. The greatest levels of locomotion were generated by injections into a region in the caudal-central nucleus accumbens, with lower levels of activity elicited by injections into more rostral or caudal regions. A similar pattern of responses was produced by administration of the indirect dopamine agonist d-amphetamine. These results indicate that there is marked heterogeneity in the response of discrete sub-regions of the nucleus accumbens to dopamine receptor stimulation and that this heterogeneity is functionally expressed in the mediation of the locomotor effects of dopaminergic agonists.