A study on withdrawal related haemodynamic response in chronic propranolol treated conscious rats.

Single dose of propranolol hydrochloride (5 mg/kg, i.p.) caused significant fall in heart rate (HR) but not in systolic blood pressure (SBP) in normotensive conscious rats. Multiple doses of propranolol (5 mg/kg, i.p., twice-a-day for 5 wk) caused significant fall in both HR and SBP at 2 wk and 4 wk in normotensive conscious rats. Sudden withdrawal of propranolol at 5 wk caused a significant blood pressure upswing and tachycardia between 12-24 h followed by normalization of both blood pressure and heart rate. The study documents a possible model of rebound hypertension in normotensive conscious rats.