Innervation Sites of Dog Hindpaw Series and Parallel Vascular Circuits

Abstract

The neural control of the distribution of blood flow between the parallel nutritional and nonnutritional vascular circuits in the dog hindpaw has been assessed. The right hindpaw of anesthetized dogs was vascularly and neurally isolated and placed in a volume recorder sealed by the skin flap. The animals were heparinized. The autoperfused preparation was isovolumetric during the control period. The inflow tubing had side arms for measurement of perfusion pressure and for injections of indicators (¹³¹I-albumin, ⁸⁶Rb and ⁸⁵Sr-microspheres). Vascular volume changes were determined from venous time-concentration curves and by plethysmography. The peripheral cut ends of the superficial and deep fibular nerves and the tibial nerve were individually stimulated at 5 and 11 Hz. The permeability surface area product of ⁸⁶Rb and the capillary filtration coefficient were determined and A-V shunt patency was assessed by the venous recovery of ⁸⁵Sr 15 µm microspheres. Each nerve stimulation increased blood flow resistance. Superficial fibular nerve innervation included essentially uniform effects on the arterioles and A-V shunts, the upstream arteries and also the veins. Deep fibular nerve stimulation indicated that its innervation included the arteries and the A-V shunt nonexchange vessels. Tibial nerve stimulations indicated that its innervation included the A-V shunt vessels and veins with minimal influences on the arteries and arterioles.