Figure 2.

Close interactions of perisynaptic astroglial and microglial processes with the synaptic elements of adjacent neurons. The boxed regions indicate specific sites of neuron-glial interactions. Perisynaptic astroglial processes (green) express the cannabinoid receptors CB1 (cyan), while microglial processes both, CB1 (cyan) and CB2 (blue) receptors in close contact to postsynaptic ECB (yellow) release sites (A). Astrocytes respond to ECB via CB1 receptors with an increase of intracellular Ca²⁺ (purple). This intracellular Ca²⁺ rise spreads (pink arrows) through the astrocyte towards distant synapses (B), where Ca²⁺-evoked release of the gliotransmitter glutamate (orange) affects neuronal physiology via presynaptic metabotropic glutamate receptors (mGluR1, brown), and generates a persistent synaptic change (B). In addition, the Ca²⁺ wave can be propagated through the gap junction-coupled astroglial syncytium (gj, light green) where on even more distant perisynaptic processes gliotransmitters (glutamate) are released as response to postsynaptic ECB liberation. Subsequently, gliotransmitters can act on postsynaptic NMDA receptors (C, brown) inducing slow inward currents.