Acquisition of a runway motor learning task is impaired by a beta adrenergic antagonist in F344 rats

Performance of rats on a motor learning paradigm that has been demonstrated to be dependent upon cerebellar norepinephrine (NE) was studied in male F344 rats treated with an α₁ antagonist (prazosin), an α₂ antagonist (yohimbine) or a β noradrenergic antagonist (propranolol). The ability of propranolol-treated rats (10 mg/kg i.p. 30 min prior to daily testing) to acquire proficiency on the novel motor task was impaired while prazosin-treated rats' (0.5 mg/kg i.p. 30 min prior to daily testing) and yohimbine-treated rats' (1 mg/kg i.p. 30 min prior to daily testing) rates of acquisition of the novel motor task were not different from controls. In an attempt to distinguish between alterations in motor coordination and motor learning, additional tests of psychomotor performance were assessed for all groups of rats. These examinations included a walking test on 2.5 and 5 cm rods and speed of running on the motor task. The data indicate that drug-treated rats show no difference from controls on the above parameters. Some differences, however, were observed between propranolol and controls in the time spent in the goal box. Overall, the data are consistent with our hypothesis that the β noradrenergic receptor is involved in the ability to acquire novel motor tasks.