Modification of cholinergic tremor by apomorphine and L-dopa in rats

Pretreatment with apomorphine, increased and prolonged the arecoline-induced tremor in rats. When given before pilocarpine, it produced different effects dependent on the dose: low doses (0.05 and 1.0 mg/kg) antagonized, but higher doses (5.0 and 10.0 mg/kg) enhanced the pilocarpine tremor. The extent and duration of arecoline tremor after pretreatment L-DOPA increased significantly, but this was not observed in the pilocarpine-induced tremor. These results suggest that the relations between striatal dopaminergic and cholinergic systems may be complex and the model based on a simple antagonism between these systems may be oversimplified.