Muscle cholinergic dilators in the sinus baroreceptor response in cats.

Experiments were done to evaluate the effect of the cholinergic vasodilator system on the flow-pressure relation in the isolated, perfused gastrocnemius and soleus muscles of the cat. Reflex changes in the muscle vascular resistance were produced by maintaining the isolated, perfused carotid sinus at different pressure levels. Flow-pressure curves were obtained from the isolated muscles at high, medium, and low carotid sinus pressures before and after administration of adrenergic or cholinergic blocking drugs or denervation, or both. Following cholinergic receptor blockade, flow-pressure relations at high sinus pressure showed a loss of a dilator component, but curves at low and medium sinus pressures were the same as controls. Following adrenergic receptor blockade, flow-pressure curves at low and medium sinus pressures were superimposed; however high sinus pressure still produced a decrease in vascular resistance. The remaining vasodilation could be abated by either denervation or antjcholinergic agents. The difference between the untreated and the cholinergically blocked flow-pressure responses represented 15-30% of the range of change in vascular resistance evoked by the sinus baroreceptor reflex. Thus, effective withdrawal of sympathetic vasoconstrictor tone did not account for total vasodilation. The data indicate that the sympathetic cholinergic vasodilator system participated in the vascular responses of skeletal muscle during baroreceptor stimulation.