Autonomic Control of Blood Flow in Hind Paw of the Dog

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Abstract
Blood flow was measured in the hind paw of the dog by directing blood from the femoral artery through an electromagnetic flowmeter and into the dorsalis pedis artery. The system was such that minimal flow was measured in skeletal muscle in the foot. Under the conditions of these experiments, epinephrine and arterenol, injected intra-arterially, exerted potent vasoconstrictor effects, the former being slightly but not significantly more potent than the latter when equimolecular doses were used. Isoproterenol and methacholine caused weak dilator responses. Ischemia did not induce any reactive vasodilation. Stimulation of the sympathetic chain at approximately the level of the first sacral vertebra induced potent vasoconstriction. All constrictor effects were blocked by 10 mg of phenoxybenzamine (Dibenzyline) given intra-arterially without affecting appreciably the dilator responses to either the methacholine or the isoproterenol. It is concluded that this vascular bed contains potent innervated alpha constrictor receptors but but that adrenergic and cholinergic dilator receptors are minimally present. No evidence was obtained for the presence of cholinergic autonomic dilator fibers.

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