Contralateral turning elicited by unilateral stimulation of dopamine D-1 and D-2 receptors in the nucleus accumbens of rats is due to stimulation of these receptors in the shell, but not the core, of this nucleus

The goal of this study was to deter-mine whether dopamine D-2 and/or D-1 receptors in the shell and the core of the nucleus accumbens of rats have a differential role in turning behaviour. Unilateral injection of a mixture of the dopamine D-2 receptor agonist quinpirole (10 mu g) and the dopamine D-1 receptor agonist 1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine-7, 8-diol (SKF 38393, 5 mu g) into the shell of the nucleus accumbens produced contralateral turning, when doses which per se were ineffective were injected. This effect was far greater than that found after similar injections into the core of the nucleus accumbens. The effect elicited from the shell was significantly attenuated by prior administration of either the dopamine D-2 receptor antagonist l-sulpiride (25 ng/0.5 mu l) or the dopamine D-1 receptor antagonist (8-chloro-2,3,4,5-tetrahydro-3-methyl-5-phenyl-1H-3-benzazepine-7-ol (SCH 23390, 0.5 mu g/0.5 mu l) into the same region. These data together with the fact that l-sulpiride is known to be a valid tool to differentiate the involvement of distinct regions within the shell underlie the conclusion that dopamine D-2 and D-1 receptors in the shell, but not the core, of the nucleus accumbens play a critical role in the contralateral turning induced by unilateral injection of dopamine receptor agonists into this nucleus. The results are discussed in view of the known output pathways of the shell.