A methodological weakness in the use of neuroleptic antagonism as a sole criterion for DAergic mediation of drug-induced behavioural effects.

Contralateral rotational behavior following unilateral injections of the GABA agonist muscimol (100 ng) or the GABA analogue baclofen (1 microgram) into the zona reticulata of the rat substantia nigra was moderately attenuated by pretreatment with haloperidol (0.4 mg/kg i.p.), but not by destruction of ipsilateral dopamine (DA) neurons induced with 6-hydroxydopamine. Antagonism by neuroleptics can erroneously indicate DAergic mechanisms in the behavioural effects of drugs if used as a sole criterion.