The study identifies monoglyceride lipase (MGL) as a key enzyme involved in the inactivation of the endocannabinoid 2-arachidonoylglycerol (2-AG). MGL, a serine hydrolase, is expressed in the brain and is localized in presynaptic terminals, where it hydrolyzes 2-AG. The research demonstrates that MGL is responsible for the primary mechanism of 2-AG inactivation in intact neurons. MGL expression was found to be highest in brain regions rich in CB1 receptors, including the hippocampus, cortex, and cerebellum. Overexpression of MGL in cortical neurons significantly reduced 2-AG accumulation, while having no effect on anandamide levels. This suggests that MGL selectively hydrolyzes 2-AG, not anandamide. The findings indicate that MGL plays a crucial role in terminating the signaling effects of endogenous 2-AG at synapses, particularly in the hippocampus. The study highlights the importance of MGL as a target for pharmacological intervention in diseases where endocannabinoids may have protective roles, such as pain and stroke. The results underscore the distinct roles of MGL and fatty acid amide hydrolase (FAAH) in the metabolism of endocannabinoids, with MGL being the primary enzyme responsible for 2-AG inactivation in vivo.The study identifies monoglyceride lipase (MGL) as a key enzyme involved in the inactivation of the endocannabinoid 2-arachidonoylglycerol (2-AG). MGL, a serine hydrolase, is expressed in the brain and is localized in presynaptic terminals, where it hydrolyzes 2-AG. The research demonstrates that MGL is responsible for the primary mechanism of 2-AG inactivation in intact neurons. MGL expression was found to be highest in brain regions rich in CB1 receptors, including the hippocampus, cortex, and cerebellum. Overexpression of MGL in cortical neurons significantly reduced 2-AG accumulation, while having no effect on anandamide levels. This suggests that MGL selectively hydrolyzes 2-AG, not anandamide. The findings indicate that MGL plays a crucial role in terminating the signaling effects of endogenous 2-AG at synapses, particularly in the hippocampus. The study highlights the importance of MGL as a target for pharmacological intervention in diseases where endocannabinoids may have protective roles, such as pain and stroke. The results underscore the distinct roles of MGL and fatty acid amide hydrolase (FAAH) in the metabolism of endocannabinoids, with MGL being the primary enzyme responsible for 2-AG inactivation in vivo.