Nature of the vasodilator and vasoconstrictor receptors in skeletal muscle of the dog.

Femomi blood flow and arterial pressure l-esponses to stimulation of the lumbar sympathetic chain at L3, L4 and L5 were compared with i-esponses to intm-arterial injections of 1-epinephrine and 1-norepinephrine before and after progressively increasing levels of adrenergic blockade, and after atropine. The vasoconstrictor i-esponses to nerve stimulation resembled most closely those caused by 1-norepinephrine injections at all levels of blockade. Atropine blocked the dilator responses to sympathetic nerve stimulation and reduced reversal responses to 1-norepinephrine injections but hurl no effect on the dilator responses to 1-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.