Activation of anaerobic metabolism in cat skeletal muscle during cholinergic sympathetic vasodilatation

Phosphorylase activity was found to increase 2-fold as compared with the control value (79% and 39% respectively) within the first 2-3 s of the vasomotor effect elicited in the skeletal muscle by sympathetic stimulation. Phosphorylase activity was still high during the period of maximum blood flow, although to a lesser extent (54% and 45%). During the phase of restoration of the initial rate of blood flow the values of phosphorylase activity were the same in the experimental and the control sample. The AMP content did not increase with the initiation of the vasomotor effect, and this fact suggests that the increase in phosphorylase activity is due to an increase in phosphorylase "a" rather than to the activation of phosphorylase "b" by AMP. Atropine blocks both the dilator effect and phosphorylase activation elicited by sympathetic stimulation. Acetylcholine, injected intraarterially or added to a muscle homogenate, increases phosphorylase activity. It is concluded that acetylcholine, released by sympathetic nerve endings, performs a second mediator function, that of activating anaerobic metabolism in the skeletal muscle. The two mediator functions of acetylcholine seem to be spatially delimited.