Cannabinoids and the endocannabinoid system have attracted considerable interest for therapeutic applications. Nevertheless, the mechanism of action of one of the main nonpsychoactive phytocannabinoids, cannabidiol (CBD), remains elusive despite potentially beneficial properties as an anti-convulsant and neuroprotectant. Here, we characterize the mechanisms by which CBD regulates Ca 2 homeostasis and mediates neuroprotection in neuronal preparations. Imaging studies in hippocampal cultures using fura-2 AM suggested that CBD-mediated Ca 2 regulation is bidirectional, depending on the excitability of cells. Under physiological K /Ca 2 levels, CBD caused a subtle rise in [Ca 2]i , whereas CBD reduced [Ca 2]i and prevented Ca 2 oscillations under high-excitability...
