Changes to MAP and arteriolar diameter as a function of perivascular NO levels. Reduction of arteriolar perivascular NO by the introduction of CFH caused a concomitant pressure response, while the change in vascular resistance at the microvascular level represented by arteriolar vasoconstriction was not present with the MP4 experimental group (A). MP4 reduced perivascular NO and increased MAP similarly in magnitude to the other CFHs, however the slight arteriolar dilation caused a statistically significant increase in arteriolar blood flow (B). Data are presented as mean ± SEM. Mean arteriolar pressure is 30 minutes after the introduction of CFH. The normal levels for each parameter are marked with dotted lines; the intersection, by a star.