Blood flow distribution following adrenergic blockade and nitric oxide production inhibition in embryonic American alligators, Alligator mississippiensis (879.4)

Abstract

Assessment of cardiovascular function in developing egg‐laying amniotes has been primarily limited to measurements made via catheters in the chorioallantoic membrane (CAM) and potentially invasive femoral and major outflow tract flow probes. Here we assess the capacity of embryonic alligators, Alligator mississippiensis, to regulate blood flow distribution using a minimally invasive microsphere distribution technique at 70 and 90% of development, in eggs incubated in normoxia or 10% hypoxia. Measurements were made in normoxia, acute 10% hypoxia, and acute 10% hypoxia following nitric oxide inhibition or alpha‐receptor blockade. We hypothesized that the embryonic response is concomitant with a redistribution of blood flow to the brain, heart, and CAM vasculature. Embryonic alligators respond to hypoxia with an initial bradycardia followed by a hypertensive tachycardia, however chronic hypoxic incubation blunts this response. Our data suggest that cardiac output is reduced during acute hypoxia in normoxic‐incubated embryos while it is maintained the hypoxic group. In addition, tonic nitric oxide dilation is present at 70% of incubation however inhibition of this tone does not modify total cardiac output at 90% of incubation. Our data suggest that hypoxic development may modify the patterns of blood flow redistribution in embryonic alligators and the mechanisms used to achieve this.Grant Funding Source: NSF CAREER IBN IOS‐0845741 to DAC