Singlet oxygen controls vasodilation through the activation of calcium signalling in astrocytes.

The central nervous system is highly active and one of the fastest consumers of oxygen. Thus, the brain requires immediate and effective oxygenation by arterial blood supply. Singlet oxygen is a non-radical form of oxygen which can be produced in cells by non-enzymatic and enzymatic means. Generation of non-toxic doses of singlet oxygen in a primary co-culture of neurons and astrocytes by 1267 nm laser induces calcium signalling in astrocytes via the induction of lipid peroxidation, activation of phospholipase C and production of IP3. [Ca2+]i rise in astrocytes triggers fusion of vesicular compartments containing ATP which in turn leads to singlet oxygen-induced calcium waves in astrocytes. Consequently, these events increase the diameter of blood vessels in the brain. Thus, these data suggest that singlet oxygen may be involved in physiological regulation of brain blood circulation and reoxygenation.