Central vascular flow patterns in the alligator, alligator mississipiensis. Malvin, Gary M., James W. Hicks, and E. Richard Greene. Institute for Basic and Applied Medical Research, The Lovelace Institutes, 2425 Ridgecrest Dr SE, Albuquerque, NM 87108
APStracts 2:0200R, 1995.
Many different flow patterns have been descibed through the central circulation of crocodilian reptiles. We tested the hypothesis that the vagus nerve stimulation promotes right-to-left (R-L) shunting in the alligator. Flow patterns were investigated before and during stimulation of the intact left vagus nerve using three methods. 1) Atrial and aortic PO2's were measured simultaneously and continuously by gas probes. 2) Atrial outflows were tracked with a blood tracer (helium). 3) Flows were assessed with echocardiography. Four different flow patterns were observed before vagal stimulation: left ventricular (LV) blood flowed into both the right (RAo) and left (LAo) aortas, while right ventricular (RV) blood flowed only into the LAo; both aortas received a mixture of LV and RV blood; only LV blood perfused both aortas; RV blood flowed into both aortas, but LV blood flowed only into the RAo. During vagal stimulation, both aortas received a mixture of LV and RV blood in half of the animals, and in the other half, both aortas received RV blood, but LV blood flowed only into the RAo. Doppler and contrast echocardiography demonstrated swirling flow in the foramen of Panizza and the base of the LAo during systole. These data indicate that vagal stimulation either maintains or produces R-L shunting, flow patterns are variable and blood can swirl in the foramen of Panizza and LAo base. 

Received 10 December 1993; accepted in final form 30 May 1995.
APS Manuscript Number R667-3.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 18 July 1995.