Hypotensive effect of bopindolol in pithed rats

1. Effects of bopindolol, a beta adrenoceptor antagonist with partial agonist activity, on the diastolic blood pressure and heart rate of pithed rats were compared with those of pindolol. 2. Both bopindolol and pindolol reduced the diastolic blood pressure (DBP) in pithed rats. Bopindolol (3.0 mg/kg) and pindolol (1.0 mg/kg) produced similar decreases in DBP of about 8 mmHg; thus pindolol had a 3-fold higher hypotensive potency when compared with bopindolol. 3. Both drugs also produced a dose-dependent decrease in heart rate. 4. Propranolol (5 mg/kg) had no antagonistic effect on the decrease in DBP produced by either bopindolol or pindolol. 5. These results suggest that both bopindolol and pindolol reduce DBP and heart rate in pithed rats through some mechanism independent of beta-adrenoceptors.