CB 1 receptor activation induces intracellular Ca 2+ mobilization and 2-arachidonoylglycerol release in rodent spinal cord astrocytes

Accumulating evidence supports the role of astrocytes in endocannabinoid mediated modulation of neural activity. It has been reported that some astrocytes express the cannabinoid type 1 receptor (CB 1 -R), the activation of which is leading to Ca 2+ mobilization from internal stores and a consecutive release of glutamate. It has also been documented that astrocytes have the potential to produce the endocannabinoid 2-arachidonoylglycerol, one of the best known CB 1 -R agonist. However, no relationship between CB 1 -R activation and 2-arachidonoylglycerol production has ever been demonstrated. Here we show that rat spinal astrocytes co-express CB 1 -Rs and the 2-arachidonoylglycerol synthesizing enzyme, diacylglycerol lipase-alpha in close vicinity to each other. We also demonstrate that activation of CB 1 -Rs induces a substantial elevation of intracellular Ca 2+ concentration in astrocytes. Finally, we provide evidence that the evoked Ca 2+ transients lead to the production of 2-arachidonoylglycerol in cultured astrocytes. The results provide evidence for a novel cannabinoid induced endocannabinoid release mechanism in astrocytes which broadens the bidirectional signaling repertoire between astrocytes and neurons.