Effect of chronic administration of propranolol on acetylcholinesterase and 5-hydroxytryptamine levels in rat brain and heart.

: The effect of chronic administration of propranolol on the rat brain and heart acetylcholinesterase was studied by administering propranolol (5mg/kg body weight) for 14 days. This treatment was found to substantially inhibit the enzyme activity. Levels of 5-hydroxytryptamine were measured in the brain and heart; in brain the levels of 5-hydroxytryptamine increased with propranolol administration, while in the heart there was no change. Effect of different concentrations of propranolol on acetylcholinesterase activity was also studied in vitro and a decreased activity of the enzyme was found in brain and heart homogenates. The significance of these results is discussed in terms of the therapeautic effects of the drug in the control of hypertension.