Glutamatergic cannabinoid receptor 1 confers neuroprotection against ischemic stroke by suppressing excitotoxicity and anoxic depolarization.

Cannabinoid receptor 1 (CB1R) is widely expressed in the brain and implicated in protection against ischemic stroke, yet its cell-type-specific functions remain incompletely understood. To systematically dissect the contributions of excitatory and inhibitory CB1R populations under ischemia, we generated mice with conditional CB1R knockout in glutamatergic (CB1RGlut-KO) or GABAergic (CB1RGABA-KO) neurons, alongside global CB1R deletion, and subjected those mice to permanent focal cerebral ischemia. Ischemic injury was evaluated using infarct volume quantification, histological staining, and neurological behavioral tests. Glutamate dynamics in the ischemic region were monitored using a fluorescent reporter iGluSnFR. The role of Glut-CB1R in synaptic transmission and anoxic depolarization was assessed via electrophysiological recordings under both baseline and ischemic conditions. We found that CB1RGlut-KO mice fully recapitulated the exacerbated ischemic injury and neurological impairment seen in global knockouts, whereas CB1RGABA-KO mice showed no significant phenotype. This functional non-redundancy was attributed to a Glut-CB1R-specific brake on excitotoxicity, as its loss elevated extracellular glutamate after ischemia. Pharmacological inhibition of glutamate N-methyl-D-aspartic acid (NMDA) receptors attenuated the exacerbated neurological deficits in CB1RGlut-KO mice. Electrophysiological recordings revealed enhanced spontaneous excitatory synaptic transmission and accelerated anoxic depolarization in CB1RGlut-KO pyramidal neurons under ischemic conditions. Pharmacological inhibition of endocannabinoid degradation conferred protection against ischemic injury in control mice but failed in CB1RGlut-KO mice, confirming that Glut-CB1R is the obligate mediator of this protection. These findings demonstrate that CB1R-mediated neuroprotection in acute, non-preconditioned ischemia is uniquely dependent on the CB1R expressed in glutamatergic neurons. Glut-CB1R represents a cell-autonomous, and therapeutically actionable target for ischemic stroke.