Astrocytes produce nitric oxide in response to cholinergic or glutamatergic stimulation

Abstract

In the brain, it had been demonstrated that nitric oxide (NO) is produced in endothelial cells and neurons by endothelial (eNOS) and neuronal nitric oxide synthase (nNOS), respectively. However, in astrocytes, the source of NO production remains uncertain. The objective of the present study is to determine the sources and activators of NO production in mouse cortical astrocytes. NOS subtypes were identified by immunocytochemistry and electron microscopy. Using cortical astrocytes in culture, NO production was evaluated using 4‐amino‐5‐methylamino‐2′,7′‐difluorofluorescein (DAF‐FM) and confocal microscopy. Elevations of NO were detected in response to a 5 min stimulation with acetylcholine, N‐Methyl‐D‐aspartic acid (NMDA) or trans‐1‐ aminocyclopentane‐1,3‐dicarboxylic acid (t‐ACPD). NO production by acetylcholine seems to be spatially restricted while NO production induced by glutamatergic stimulation is diffuse. These effects were blocked by the NOS competitive inhibitor L‐N‐Nitro‐ Arginine, thus confirming their specificity. Our results suggest that there are two different pathways for NO production in astrocytes, which could have physiological consequences for neuronal and vascular functions in the brain. Supported by NSERC