THE ROLE OF THE AUTONOMIC NERVOUS SYSTEM IN THE REGULATION OF HEART PHOSPHORYLASE IN THE OPEN-CHEST RAT

¹ Department of Pharmacology, Schools of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania

The effect of the autonomic nervous system on cardiac Phosphorylase has been studied with the open-chest rat preparation.

Electrical stimulation of the vagus or injection of acetylcholine produced a marked decrease in phosphorylase a activity, accompanied by a fall in mean arterial blood pressure and bradycardia. Hypotension induced by acute hemorrhage did not affect cardiac phosphorylase activity.

Injection of dimethylphenylpiperazinium (DMPP) into atropinized, normal and adrenalectomized rats produced an increase in phosphorylase a with a concomitant hypertension and increase in force of contraction.

Stimulation of sympathetic ganglia by injection of various doses of McNeil-A-343 (4-(m-chloro-phenylcarbamoyloxy)-2-butynyltrimethylammonium chloride) produced proportional increases in phosphorylase a activity and blood pressure. The enzymatic and cardiovascular stimulating effects of McNeil-A-343 were amitagonized by acetylchohine.

Because of the remarkable correlation between the activity of cardiac phosphorylase a and the functional changes induced by autonomic stimulation, it was concluded that there is a significant, but as yet unknown, relationship between the level of phosphorylase activity and the contractile processes of the heart.