This study investigates the synaptic-like transmission between neural axons and arteriolar smooth muscle cells (aSMCs) in the mouse cerebral cortex, which is crucial for neurovascular coupling (NVC). Using two-photon focal optogenetics, the researchers demonstrate that single glutamatergic axons dilate their innervating arterioles through synaptic-like transmission at the junctions between neural and aSMC cells. The presynaptic boutons form dual innervations on both dendrites and aSMCs, which express various neuromediator receptors, including low levels of glutamate NMDA receptor subunit 1 (Grin1). Disrupting NMDA receptor function in aSMCs by aSMC-specific knockout of Grin1 reduces optogenetic and whisker stimulation-induced functional hyperemia. Notably, this disruption also reduces brain atrophy following cerebral ischemia by preventing Ca2+ overload in aSMCs during arteriolar constriction caused by ischemic spreading depolarization. The findings reveal that NMDA receptor-mediated synaptic-like transmission between neural axons and aSMCs drives NVC and opens new avenues for studying stroke.This study investigates the synaptic-like transmission between neural axons and arteriolar smooth muscle cells (aSMCs) in the mouse cerebral cortex, which is crucial for neurovascular coupling (NVC). Using two-photon focal optogenetics, the researchers demonstrate that single glutamatergic axons dilate their innervating arterioles through synaptic-like transmission at the junctions between neural and aSMC cells. The presynaptic boutons form dual innervations on both dendrites and aSMCs, which express various neuromediator receptors, including low levels of glutamate NMDA receptor subunit 1 (Grin1). Disrupting NMDA receptor function in aSMCs by aSMC-specific knockout of Grin1 reduces optogenetic and whisker stimulation-induced functional hyperemia. Notably, this disruption also reduces brain atrophy following cerebral ischemia by preventing Ca2+ overload in aSMCs during arteriolar constriction caused by ischemic spreading depolarization. The findings reveal that NMDA receptor-mediated synaptic-like transmission between neural axons and aSMCs drives NVC and opens new avenues for studying stroke.