Nigrostriatal dopaminergic control of operant and spatial behavior in the rat

Rats trained in a two-lever Skinner box to obtain food by leverpressing were given either a unilateral 6-0HDA lesion of the nigrostriatal bundle on the same side as or on the side opposite to the preferred forepaw or a control treatment, and were tested 1 week and 8 weeks after surgery. Only subjects in the contralaterally lesioned group reversed their forepaw preferences. Rate of leverpressing was depressed in all lesioned subjects, but more so in contralaterally lesioned ones. All lesioned subjects rotated mainly ipsiversively. Another group of rats given a unilateral kainate lesion of the striatum contralateral to the preferred forepaw and tested 1 week postoperatively displayed a reversal of forepaw preferences, a depression of leverpressing, and an increased preference for the lever opposite to the lesioned striatum. In a third experiment, rats trained to run a T·maze for food and then given a uni· lateral 6-0HDA lesion of the nigrostriatal bundle opposite to the preferred arm of the maze and tested 1 week later showed a reversal of side preferences. It is proposed that the nigrostriatal DA system is part of a lateralized system controlling forelimb use, rotational behavior, and side preference in a T·maze.