The frequency of each type of non-SER compartment (cp, coated pits; cv, coated vesicles;lv, large vesicles; te, tubular endosomes; cplx, MVB–tubule complexes;sv, small vesicles; av, amorphous vesicles; avc, amorphous vesicular clumps) in dendrites. The location of the compartment was determined to be in spines (1: in a spine head or neck), at the base of the spine (2), or in the shaft of the dendrite (3), as shown in the inset.