Effect of cessation of propranolol treatment on myocardial noradrenaline and acetylcholine content in the rat.

Cessation of long-term treatment of rats with propranolol 10 mg/kg/day subcutaneously produced no alteration in the myocardial noradrenaline content estimated 12, 24, 48 and 96 hours after the last propranolol injection; nor did the myocardial acetylcholine content change. These results do not support the idea that the withdrawal-rebound phenomenon caused by abrupt cessation of propranolol therapy is associated with an accumulation of the autonomic neurotransmitters in myocardial tissue.