Rationale: Using electron microscopy, anti-CB1 immunogold particles were found on mitochondrial membranes on presynaptic terminals of the CA1 region (as well as in the presynaptic plasma membrane: SynGO ID 807). Mitochondrial and plasma membrane staining are lost in CB1 knock out animals (CB1-/-). Rescued expression of CB1 by injection of an adeno-associated virus expressing CB1 (AAV–CB1) on CB1-/- mice recovers mitochondrial and plasma membrane localization. When a variant of CB1 with a deletion of the first 22 N-terminal amino acids is expressed on CB1-/- background mitochondrial localization is lost, although this variant is still localized to the presynaptic plasma membrane.. Experimental description: ...mice (n = 3 per group) were processed for electron microscope pre-embedding immunogold labelling as previously described...