STIMULATION OF ACETYLCHOLINE OR DOPAMINE-RECEPTORS IN THE NUCLEUS-ACCUMBENS DIFFERENTIALLY ALTERS DOPAMINE RELEASE IN THE STRIATUM OF FREELY MOVING RATS

The present study examined whether unilateral stimulation of acetylcho line or dopamine receptors in the nucleus accumbens induces an asymmet ry in dopamine transmission in the ventrolateral striatum. For this pu rpose, a microdialysis technique was used to measure dopamine release in both sides of the ventrolateral striatum following unilateral injec tions of carbachol (5 mu g/0.5 mu l) or a mixture of dopamine D-1 and dopamine D-2 receptor agonists henyl-2,3,4,5-tetrahydro-1H-3-benzazepi ne-7,8-diol 5 mu g + quinpirole 10 mu g/0.5 mu l) into the nucleus acc umbens. The results show that carbachol injection increased dopamine r elease in the ipsilateral striatum without changing dopamine release i n the contralateral striatum, whereas the dopamine D-1/D-2 receptor ag onist mixture injected unilaterally into the nucleus accumbens produce d an increase followed by a decrease in dopamine release in the ipsila teral striatum, but only a decrease in dopamine release in the contral ateral striatum. The biochemical effects of the cholinergic treatment greatly outlasted the drug-induced contralateral turning, whereas the biochemical effects of the dopaminergic treatment showed a good correl ation with the drug-induced contralateral turning. The present study p rovides biochemical evidence that unilateral stimulation of acetylchol ine or dopamine receptors in the nucleus accumbens elicits an asymmetr y in dopaminergic activity in the ventrolateral striatum. The present study also provides biochemical evidence that two distinct neural subs trates are involved in the effects of cholinergic and dopaminergic man ipulation of the nucleus accumbens.