Physiological and psychological effects of ±-propranolol, +-propranolol and diazepam in induced anxiety

1 Four equal-sexed groups of eight normal subjects were given single doses of either (±)-propranolol (120 mg), (+)-propranolol (120 mg), diazepam (6 mg) or placebo using double-blind procedure and their effects studied under three types of experimental stress and at rest. 2 Finger tremor, EEG, averaged auditory evoked response, skin conductance, heart rate and respiratory rate were measured at each time of testing, and subjects also completed performance tests (reaction time, tapping speed and symbol copying) and subjective mood scales. 3 Neither (+)- nor (±)-propranolol had any beneficial effects on mood and physiological tests showed that, although adequate β-adrenoceptor blockade was achieved, there was no evidence of sedation. 4 Diazepam reduced subjective anxiety, significantly lessened the main amplitude of the auditory evoked response and also reduced the proportion of slower rhythms in the EEG. 5 The results suggest that (+)- and (±)-propranolol have no psychotropic effects on induced anxiety and that their modes of action are fundamentally different from that of diazepam.