Independent GABAergic and cholinergic modulation of apomorphine-induced stereotyped rearing in the rat

The injection of GABA into the caudate nucleus inhibited the stereotyped rearing induced by apomorphine in a dose-related manner. Muscimol, a potent GABAergic agonist shared this effect. The inhibitory effect of GABA was easily counteracted by bicuculline but not by pretreatment with atropine. Injection of carbachol into the caudate nucleus inhibited the stereotyped rearing induced by systemically-applied apomorphine in a dose-related manner. This inhibitory effect was easily abolished by atropine but not bicuculline. Thus, the stereotyped rearing induced by apomorphine, an effect due to an increased excitatory state of the dopaminergic system in the caudate nucleus, could be modified (inhibited) by augmentation of either the GABAergic or of the cholinergic state excitation. The two modulatory systems did not appear to be interlinked; most probably, they influence the dopaminergic effect independently of one another.