Dorsal striatal mechanisms involved in the dopamine D 2 receptor-mediated potentiation of apormorphine-induced jaw movements

Abstract

The role of dorsal striatal mechanisms in the regulation of apomorphine-induced jaw movements was studied. Jaw movements induced by apomorphine (0.2 mg/kg i.v.) were potentiated by quinpirole (10 μg/0.2 μl) injected into the dorsal part of the striatum 10 min before apomorphine. Quinpirole injection into the ventral part of the striatum did not affect the effects of apomorphine. The quinpirole-induced potentiation in the dorsal striatum was prevented by l-sulpiride (25 ng), nemonapride (1 μg), SCH23390 (1 μg) or methylscopolamine (1 μg), but not muscimol (50 ng), co-administered with quinpirole. Injection of these drugs alone 10 min before apomorphine failed to alter the effects of apomorphine. l-Sulpiride (25 ng) injected into the dorsal striatum 60 min before apomorphine increased the frequency of jaw movements induced by apomorphine (0.2 mg/kg). The l-sulpiride-induced potentiation was prevented by methylscopolamine (0.1 μg) or l-sulpiride (25 ng) injected into the dorsal striatum 10 min before apomorphine; we had already found that this potentiation was also blocked by SCH23390. It is suggested that a synergistic dopamine D 1/D 2 receptor interaction underlies both the quick-onset potentiation by quinpirole and the delayed-onset potentiation by l-sulpiride.