Muscimol microinfused into the nigrotegmental target area blocks selected components of behavior elicited by amphetamine or cocaine.

We examined whether behaviors elicited by systemic administration of the stimulants amphetamine and cocaine involve the relay of outflow from basal ganglia to the target region of the GABAergic nigrotegmental pathway (nigrotegmental target area: NTT), in the region of the pedunculopontine nucleus. Bilateral microinfusions of the GABAA agonist muscimol (25 ng in each side) were administered into the NTT in stimulant-treated rats. Amphetamine- and cocaine-induced stereotyped sniffing and repetitive head movements were totally abolished by muscimol infusions. In contrast, stimulant-induced locomotion and snout contact fixation were spared or enhanced. These observations, which extend those of Childs and Gale (1983b) with apomorphine-induced gnawing, further implicate the GABAergic nigrotegmental pathway in the mediation of basal ganglia-related motor dysfunction. On the other hand, cocaine- and amphetamine-induced locomotion and snout contact fixation do not appear to depend upon mediation through GABA-receptive neurons in the NTT. Thus, the NTT may be selective for the processing of outflow from the basal ganglia.