Concentration-response curves for adenosine agonist mediated vasodilation in (A) mouse, and (B) rat hearts. Responses to adenosine (n=8 for mouse, n=7 for rat), 2-chloroadenosine (n=7 for mouse, n=7 for rat), R-PIA (n=6 for mouse, n=8 for rat), NECA (n=7 for mouse, n=7 for rat), and CGS 21680 (n=8 for mouse, n=7 for rat) were studied. Responses are shown as per cent of baseline coronary resistance. All values are means±s.e.mean.