Fig. 7: Schematic of the astrocytic mechanism closing a positive feedback loop targeting dendritic spiking.

Active pyramidal cells (red) trigger the release of endocannabinoids, which act on astrocytic CB1 receptors and thereby increase extracellular D-serine levels. This leads to increased opening of NMDARs, a lower threshold of dendritic spikes and a higher NMDAR component. This positive feedback loop is primarily engaged by theta-like activity of pyramidal cells.