Adenosinergic regulation of the cardiovascular system in the red-eared slider Trachemys scripta

Few studies have investigated adenosinergic regulation of the cardiovascular system in reptiles. The haemodynamic effect of a bolus intra-arterial adenosine injection (2.5 μM kg⁻¹) was investigated in nine anaesthetised red-eared sliders (Trachemys scripta). Adenosine caused a transient bradycardia, which was accompanied by systemic vasodilatation as evidenced by an increase in systemic flow and a decrease in systemic pressure. Meanwhile, pulmonary flow fell significantly. Both the bradycardia and increase in systemic conductance were significantly attenuated by theophylline (4 mg kg⁻¹), demonstrating an involvement of P₁ receptors. These results suggest that adenosine is likely to play a significant role in reptile cardiovascular physiology. In turtles specifically, adenosinergic regulation may be particularly relevant during periods of apnoea.