Figure 1.

Schematic view of potential localizations of CB₁ receptors at the synapse. CB₁ receptors are present at both presynaptic terminals and postsynaptic compartments of neurons and on astrocytes, exerting different impacts at the tripartite synapse. Whereas the presynaptic plasma membrane localization is long recognized, new evidence points to the presence of CB₁ at mitochondrial membranes of both presynaptic and somatodendritic compartments of neurons, although their specific functions are still to be fully determined. The presence of CB₁ at postsynaptic plasma membranes is possible, but no direct anatomical evidence for this exists so far. Endosomal CB₁ expression has been also proposed by different studies. CB₁ (and possibly mtCB₁) receptors are present in astrocytes, where they control astroglial synaptic functions. For additional information see the main text.