The vasodilatation produced by carbon dioxide is maximum in:

Inhalation of 7% CO2 increases cerebral blood twofold. Cerebral blood vessels are very sensitive to CO2 tension. Hepatic aerial system is sensitive to adenosine; it brings about vasodilatation. Adenosine is the most impoant vasodilator of coronary vessels. CO2, H+, K+, hypoxia also cause reactive hyperemia. NO, an endothelium-derived relaxing factor is an impoant vasodilator of renal aerioles.