Blood flow redistribution during spontaneous wheel walk of the rat.

Changes in regional blood flow and arterial pressure in the rat during spontaneous walk in a wheel were observed. An electromagnetic flow probe was implanted around the carotid, superior mesenteric, or renal artery, or the terminal aorta and a catheter for pressure measurement was inserted into the terminal aorta or the common carotid artery. The wheel had a diameter of 35 cm and rotated passively as the rat walked. When hindquarter (terminal aortic) flow increased markedly during wheel walk, carotid flow decreased, superior mesenteric flow decreased or remained unchanged, and renal flow did not change. Arterial pressure remained almost unchanged and heart rate increased an average of about 10%. Semiquantitative considerations indicated that arterial pressure was maintained in the face of the profuse increase in hindquarter flow during wheel walk by an increase in cardiac output rather than shifts of blood flow from other regions.