Noboru Toda and Tomio Okamura
Department of Pharmacology, Shiga University of Medical Science, Seta,
Ohtsu 520-2192, Japan
Abstract: The vascular tone, vascular resistance and blood flow
in the brain are regulated by neural and humoral factors in quite a different
way from those of peripheral organs and tissues. In contrast to the dominant
vasoconstrictor control in the periphery, the intracranial vascular tone
is predominantly influenced by vasodilator mediators over vasoconstrictor
ones. Recent studies have revealed that nitroxidergic vasodilator nerve
and endothelium-derived hyperpolarizing factor (EDHF) or K+ channel
opening substance appear to play important roles in the regulation of cerebral
arterial and arteriolar tone in primate and subprimate mammals, in addition
to the accepted information concerning the crucial contribution of endothelium-derived
relaxing factor (EDRF) or nitric oxide (NO), polypeptides, prostanoids,
etc. This article summarizes characteristic properties of vasodilator factors
in controlling the cerebral arterial and arteriolar tone that undoubtedly
contribute to circulatory homeostasis. The content includes vasodilator
nerve, endogenous vasodilator substances, and vasodilator interventions
such as hypoxia, hypercapnia and hyperosmolarity.
Keywords: Cerebral artery, Vasodilator nerve, Vasodilator substance,
Vasodilator intervention, Nitric oxide