Specific asymmetric behaviour induced by the direct chemical stimulation of neostriatal dopaminergic mechanisms

Summary The role of neostriatal dopamine in the control of motor function was investigated by assessment of the asymmetric motor behaviour resulting from the unilateral intracaudate administration of pharmacological and neurochemical substances. The unilateral intracaudate administration of 100 g dopamine to saline pretreated rats induced a mild contralateral asymmetry but lower doses of dopamine were ineffective. Dopamine was similarly active by intrapallidal injection but no asymmetries were observed following injections into the thalamus, nucleus lateralis septi, cerebral cortex or area preoptica. Pretreatment with haloperidol, nialamide or a combination of these two agents increased the sensitivity of caudate tissue to the dopamine effect. This enhancement was shown to be specific for the neuroleptic agents (haloperidol, clothiapine and oxypertine were effective whilst aceperone and phenoxybenzamine were relatively ineffective) and the contralateral behaviour specific for dopamine (noradrenaline, RS 86, procaine, chlorpromazine, trifluphenazine, amitriptyline and protripytline were ineffective) although a contralateral asymmetry was observed following unilateral intracaudate atropine or 5-hydroxytryptamine but these could be differentiated from the dopamine effect. The action of dopamine was mimicked by dopamine agonists and abolished by ablation of the substantia nigra.