Effects of clenbuterol and prenalterol on behavior maintained under a multiple fixed-interval, fixed-ratio schedule

The results of a number of studies have implicated beta adrenergic receptors in the brain in the actions of proven antidepressant drugs. This suspected involvement of central beta adrenergic receptors made it of interest to characterize the behavioral effects of centrally acting beta adrenergic agonists. Clenbuterol and prenalterol, unlike most beta adrenergic agonists, penetrate into the central nervous system after peripheral administration. In the present study, the effects of these agonists on behavior maintained under a multiple fixed-interval 5-min, fixed-ratio 30-response schedule were determined. Both compounds, in a dose-dependent manner, reduced response rate under both components of the multiple schedule. Under the fixed-interval component, clenbuterol and prenalterol altered the temporal pattern of responding. At no dose tested was there evidence for any stimulant action of either of the drugs. The effects of clenbuterol and prenalterol on behavior maintained under the multiple schedule appeared to be a result of an interaction of the agonists with beta adrenergic receptors. This was evidenced by the ability of the beta adrenergic antagonist propranolol to block the effects of the agonists. The behavioral effects of clenbuterol and prenalterol appear, in general, to be similar to effects reported previously for tricyclic and monoamine oxidase inhibiting antidepressant drugs.