Central effects of beta-adrenoceptor antagonists. I--Performance and subjective assessments of mood

1. Central effects of the beta-adrenoceptor antagonists, propranolol (40, 80 and 160 mg) and atenolol (50 and 100 mg) were studied in 12 healthy male subjects. Two placebo ingestions and an active control (oxazepam 15 mg) were included. Single doses were administered double-blind at 11.00 h, and assessments of performance and subjective feelings were made before, 2 h and 4 h after ingestion. 2. Performance was measured using letter cancellation, digit symbol substitution, continuous attention, choice reaction time, finger tapping, short term and immediate memory, critical flicker fusion and two flash fusion. Subjective feelings were assessed using twelve visual-analogue scales. 3. Oxazepam impaired performance at letter cancellation (P less than 0.001), digit symbol substitution (P less than 0.05), continuous attention (P less than 0.001), immediate recall (P less than 0.05) and finger tapping (P less than 0.05), but neither of the beta-adrenoceptor antagonists affected these measures. Propranolol (40 and 160 mg) also impaired short term memory (P less than 0.05), though it was not possible to establish this effect with atenolol. 4. Subjective alertness was reduced by oxazepam (P less than 0.01) and atenolol (P less than 0.05), while propranolol (40 mg) reduced anxiety (P less than 0.01) and propranolol (80 mg) impaired ability to concentrate (P less than 0.05). 5. The results suggest that both lipophilic and hydrophilic antagonists modify the central nervous system, though impairment may be difficult to establish with conventional tests. The observations on memory and alertness suggest that the central effect of beta-adrenoceptor antagonists may be subtle.