Please use this link to access this publication. Abstract Cannabis and cannabinoid drugs are central agents that are used widely recreationally and are employed broadly for treating psychiatric conditions. Cannabinoids primarily act by stimulating presynaptic CB1 receptors (CB1Rs), the most abundant G-protein-coupled receptors in brain. CB1R activation decreases neurotransmitter release by inhibiting presynaptic Ca2+ channels and induces long-term plasticity by decreasing cellular cAMP levels. Here we identified an unanticipated additional mechanism of acute cannabinoid signaling in presynaptic terminals that regulates the size of synaptic vesicle pools available for neurotransmitter release. Specifically, we show that activation of CB1Rs in human and mouse neurons rapidly recruits...