Alpha noradrenergic agonists promote catalepsy in the mouse

Alpha adrenergic receptors are important in motor control. Adrenergic drugs reportedly modulate the catalepsy caused by other agents, such as opiates and neuroleptics. We tested a variety of adrenergic agonists and blockers in a nondrug, mouse model of catalepsy. A major cataleptic effect was produced by both alpha agonists, phenylephrine (0.5 to 3 mg/kg, IP) and clonidine (0.5 to 2 mg/kg), and this catalepsy was antagonized by pretreatment with both of the respective antagonists, phenoxybenzamine (alpha-1) and yohimbine (alpha-2) (p less than 0.0001). The mixed beta agonist, isoproterenol (2 mg/kg), appeared to have a minor cataleptic effect, and this was abolished by beta antagonist. Open-field locomotor scores during the same treatments revealed that catalepsy and hypokinesia are dissociable.