Beta adrenoceptor blockade mimics effects of stress on motor activity in mice

Reduced central noradrenergic function has been implicated as a factor in reduced behavioral activity after stress. The present studies examined the role of reduced beta adrenergic neurotransmission in mediating this effect. This was done by testing the ability of beta receptor antagonists to mimic the behavioral actions of stress. Mice were subjected to stress or given various beta antagonists and tested for swimming behavior, locomotor activity, or grooming behavior. As previously reported, stress reduced swimming and locomotor activity and increased grooming. Both the nonselective antagonist, l-propranolol, and the beta-1 selective antagonist, betaxolol, produced the same effects as stress on all three measures. A beta-2 selective antagonist, ICI 118,551, was effective only on swimming, whereas a membrane stabilizing agent, d-propranolol, was effective only on grooming behavior. The peripherally active beta-1 antagonist, atenolol, was not effective on any measure. The nonspecific dopaminergic receptor blocker, fluphenazine, reduced locomotion but tended also to reduce grooming. The results indicate that blockade of beta-1 receptors in the CNS selectively mimics the action of stress on gross motor activity in mice and, along with previous data, suggest that stress leads to a relative deficiency in central beta-1 noradrenergic neurotransmission in these animals.