Neural control of nutritional and nonnutritional circuits in the dog hindpaw

The neural control of blood flow and volume distribution between parallel nutritional and nonnutritional circuits has been investigated in the vascularly and neurally isolated dog hindpaw. Twelve paws were perfused by controlled pressure and ten paws were perfused by controlled flow via the cranial tibial artery. Venous outflow was measured and collected from the lateral saphenous vein. The superficial and deep fibular nerves and the tibial nerve were cut and individually stimulated, resulting in rates which at least doubled the blood flow resistance. Vascular volume changes were measured by injections of 51Cr-labeled red cells and 131I-labeled albumin. Tissue volume changes were measured by plethysmography. Capillary diffusion capacity was calculated from 86Rb extractions, and capillary filtration coefficients were determined. Superficial fibular nerve and deep fibular nerve stimulations apparently resulted in nonnutritional circuit constriction with resulting blood flow redistribution to nutritional circuits, possibly located in tissues other than the skin, e.g., adipose tissue. Tibial nerve stimulation caused no redistribution of blood flow between the two circuits presumably due to a uniform constriction of arteries and small vessel segments.