OXYGEN UPTAKE IN SKELETAL MUSCLE OF ANESTHETIZED DOG DURING SYMPATHETIC VASODILATATION

Oxygen uptake in dog skeletal muscle was studied upon activation of the sympathetic cholinergic vasodilator nerves, upon reflex inhibition of the peripheral vasoconstrictor nervous tone and as a response to i.a. acetylcholine infusion. Oxygen uptake was calculated from the arteriovenous oxygen saturation and the blood flow. Stimulation of the hypothalamic vasodilator area or of the sympathetic lumbar chain, after adrenergic nervous blockade, produced an increased blood flow and a rise in calculated oxygen uptake in the muscle. In most animals the oxygen uptake returned to, or went slightly below, pre‐stimulatory levels after an initial increase for about 30 sec. However, in some experiments the oxygen uptake was elevated during the whole period of vasodilatation. Reflex inhibition of vasoconstrictor tone was produced in crosscirculation experiments by stimulating the carotid sinus nerve of the recipient dog. When the stimulation resulted in a blood flow rise in the cross‐circulated muscle, the oxygen uptake in the muscle remained increased during the whole period of vasodilatation. Acetylcholine was infused i.a. to produce vasodilatations comparable to those induced by vasodilator nerve stimulation or reflex inhibition of vasoconstrictor tone. A blood flow rise was accompanied by an initial brief inctease of the oxygen uptake followed by a return to resting values. It is concluded that sympathetic cholinergic nervous stimulation and acetylcholine elicit changes in the oxygen uptake in skeletal muscle indicating an effect predominantly on precapillary resistance vessels and not, or to a much lesser extent, on precapillary sphincters. In contrast, by inhibition of vasoconstrictor nervous tone both precapillary resistance vessels and precapillary sphincters are dilated. © 1969 Scandinavian Physiological Society