Nature of the Vasodilator and Vasoconstrictor Receptors in Skeletal Muscle of the Dog

Femoral blood flow and arterial pressure responses to stimulation of the lumbar sympathetic chain at L3, L4 and L5 were compared with responses to intra-arterial injections of l-epinephrine and l-norepinephrine before and after progressively increasing levels of adrenergic blockade, and after atropine. The vasoconstrictor responses to nerve stimulation resembled most closely those caused by l-norepinephrine injections at all levels of blockade. Atropine blocked the dilator responses to sympathetic nerve stimulation and reduced reversal responses to l-norepinephrine injections but had no effect on the dilator responses to l-epinephrine. It is concluded that, in skeletal muscle, there are three types of vasoreceptors under autonomic control. Two of these, one constrictor and one dilator, are innervated; the third, a dilator receptor, is only under hormonal control.