Differential sensitivity to the effects of albuterol on locomotor activity and operant behavior.

The purpose of the present study was to determine the effects of the beta-2 selective adrenergic agonist albuterol on three behaviors, locomotor activity, behavior maintained under a differential-reinforcement-of-low-rate (DRL) schedule, and behavior maintained under a multiple fixed-interval, fixed-ratio (FI-FR) schedule of reinforcement. Albuterol reduced response rate under the DRL schedule in a manner that resulted in an increase in reinforcement rate. Similarly, albuterol reduced response rate under both components of the multiple FI-FR schedule in a dose-dependent manner. The ED50 values for the effects of albuterol on these two operant behaviors were calculated to be approximately 1 mg/kg and the minimal effective doses were 0.3-1 mg/kg. In addition to affecting operant behavior, albuterol also reduced locomotor activity; the ED50 values and minimal effective doses were 0.05 and 0.03 mg/kg, respectively. The effects of albuterol on DRL behavior, FI-FR behavior and locomotor activity were antagonized by the beta adrenergic antagonist propranolol; this suggests that the behavioral effects of this agonist were mediated, at least in part, by beta adrenergic receptors. The differential sensitivity of locomotor activity and operant behavior to albuterol suggests that the actions of this drug on locomotor activity may be mediated predominantly by peripheral beta adrenergic receptors and that its effects on operant behavior may be mediated by beta adrenergic receptors in the central nervous system.