GUT BLOOD-FLOW IN THE ESTUARINE CROCODILE, CROCODYLUS-POROSUS

Simultaneous recordings of blood flow in the right and left aorta and carotid and coeliac artery were made in the crocodile,Crocodylus porosus at rest and during various stimuli. In resting animals the right aorta and carotid artery flow profiles resembled the recordings obtained in the caiman (Axelsson et al. 1989a), with an anterograde blood flow throughout the cardiac cycle. As in the caiman, the left aorta flow profile was complex with both anterograde and retrograde blood flow during the cardiac cycle, and a net left aorta blood flow near zero at rest. The coeliac artery blood flow profile did not show the complex pattern seen in the upper aorta, immediately suggesting that most of the coeliac artery blood originates elsewhere. We believe that coeliac artery blood flow in the resting animal derives from the right aorta via the abdominal anastomosis between the two aortas. Feeding induced an increase in the coeliac artery and left aorta blood flow, probably due to a decrease in visceral vascular resistance, and hence coeliac arterial and the left aorta blood pressure, which facilitates blood flow (from right to left aorta) through the foramen of Panizza. During short 'fright dives', heart rate fell and there was a decrease in the recorded blood flows: carotid artery blood flow did not decrease to the same extent as the RAo and coeliac artery flow, indicating some capacity for redistribution of blood to the cephalic circuits during diving. Similarly, a near-unimpaired carotid artery blood flow was maintained after adrenaline injection. Substance P increased the coeliac artery blood flow and produced a right-to-left cardiac shunt, probably by construction of the pulmonary vasculature.