The role of adenosine in hypercarbic hyperemia: in vivo and in vitro studies in adenosine 2A receptor knockout and wild-type mice: Laboratory investigation

Object The authors tested the hypothesis that adenosine, acting through the A2A receptor, is not involved in hypercarbic hyperemia by assessing the effects of increased PaCO2 on cerebral blood flow (CBF) in vivo in wild-type and A2A receptor knockout mice. In addition, they evaluated the effect of abluminal pH changes in vitro on the diameter of isolated perfused penetrating arterioles harvested from wild-type and A2A receptor knockout mice. Methods The authors evaluated in a blinded fashion the CBF response during transient (60-second) hypercapnic (7% CO2) hypercarbia in anesthetized, ventilated C57Bl/6 wild-type and adenosine A2A receptor knockout mice. They also evaluated the hypercarbic response in the absence and presence of the nonselective and selective adenosine antagonists. Results Cerebral blood flow was measured using laser Doppler flowmetry. There were no differences between the CBF responses to hypercarbia in the wild-type and the knockout mice. Moreover, the hypercarbic hyperemia response wa...