DYSTONIC POSTURING AND CIRCLING BEHAVIORS INDUCED BY DOPAMINERGIC AGENTS IN RATS WITH UNILATERAL GLOBUS-PALLIDUS LESIONS

The present study examined the behavioral effects of dopamine receptor agonists, antagonists, or N-methyl-D-aspartate (NMDA) glutamate recep tor antagonist in rats with a unilateral excitotoxic lesion of the glo bus pallidus (GP). After the unilateral CP lesions were made by inject ions of the ibotenic acid, drugs were systemically given and the elici ted behaviors were quantitatively assessed. Systemic administration of haloperidol, but not SCH23390, dose-dependently induced contraversive dystonic posturing in unilateral GP-lesioned rats. On the other hand, systemic administration of quinpirole, but not SKF38393, induced ipsi versive circling. MK-801, only when given at a high dose, caused ipsiv ersive circling with dystonic posturing. The present results showed th at, in unilateral GP-lesioned rat, the D2 receptor agonist and antagon ist caused ipsiversive and contraversive posturing or circling, respec tively. Since the rotational behavior is induced on the basis of asymm etry of the basal ganglia output activity, there must be a marked diff erence between the GP ablation and the administration of D2 receptor b lockade on the basal ganglia output activity, supporting a speculation that overactivity of the basal ganglia under dopamine depletion is no t solely a result of the disinhibition from the inhibitory GP efferent s. The present unilateral GP-lesion model appears to be a useful one f or the pharmacobehavioral investigation of D2-mediated mechanisms. (C) 1998 Elsevier Science B.V.