Cannabinoid CB1 receptors regulate neuronal TNF-α effects in experimental autoimmune encephalomyelitis

Cannabinoid CB1 receptors (CB1Rs) regulate the neurodegenerative damage of experimental autoimmune encephalomyelitis (EAE) and of multiple sclerosis (MS). The mechanism by which CB1R stimulation exerts protective effects is still unclear. Here we show that pharmacological activation of CB1Rs dampens the tumor necrosis factor α (TNFα)-mediated potentiation of striatal spontaneous glutamate-mediated excitatory postsynaptic currents (EPSCs), which is believed to cogently contribute to the inflammation-induced neurodegenerative damage observed in EAE mice. Furthermore, mice lacking CB1Rs showed a more severe clinical course and, in parallel, exacerbated alterations of sEPSC duration after induction of EAE, indicating that endogenous cannabinoids activate CB1Rs and mitigate the synaptotoxic action of TNFα in EAE. Consistently, we found that mice lacking the fatty acid amide hydrolase (FAAH), and thus expressing abnormally high brain levels of the endocannabinoid anandamide, developed a less severe EAE associated with preserved TNFα-induced sEPSC alterations. CB1Rs are important modulators of EAE pathophysiology, and might play a mechanistic role in the neurodegenerative damage of MS patients.