Meeting Abstract

P3.8  Tuesday, Jan. 6  Assessing the capacity for sympathetic control of cardiovascular physiology in embryonic snapping turtles (Chelydra serpentina) TATE, KB*; EME, J; CROSSLEY II, DA; University of North Dakota; University of California, Irvine; University of North Dakota kevin.tate@und.edu

Control of cardiovascular function during development of amniotic vertebrates remains poorly understood, particularly for reptiles. We have previously determined that an active cholinergic and adrenergic tone on cardiovascular function is present late in the embryonic development of snapping turtles. However, the source of the adrenergic tone, whether circulating hormones or the autonomic nervous system, is unknown. In this study, sequential pharmaceutical sympathectomy and receptor blockade was utilized to isolate the source of the adrenergic tone in embryonic snapping turtles. Initially, pharmacological sympathectomy with 6-hydroxydopamine increased arterial pressure, which remained elevated for the duration of the experiment, while heart rate transiently increased. This treatment was followed by injection of receptor blocking agents. Administration of the muscarinic antagonist, atropine, increased heart rate and had minimal impact on arterial pressure. The beta-adrenergic antagonist, propranolol, induced a marked decrease in heart rate, while arterial pressure transiently increased. Finally, administration of the alpha-adrenergic antagonist, phentolamine, caused a marked decrease in arterial pressure without affecting heart rate. Collectively, data support the previously established presence of cholinergic and adrenergic tone in this embryonic reptile, and suggest that the adrenergic response may originate primarily from circulating catecholamines in snapping turtle embryos at 90% of development.