Fig. 4.

Small vesicles in dendrites. a, A large vesicle (arrowhead) next to a small vesicle (arrow) in a spine head. Note the distinctive difference in size. b, A small vesicle (arrow) in a spine head with a tubular compartment that has a coated tip (arrowhead). c, d, Adjacent serial sections showing a tubular compartment (c, arrowhead) with a small vesicle (d, arrow) of the same diameter near its tip. e, A small vesicle-sized omega figure (arrow) in the plasmalemma at the base of a thin spine (s). A cross-sectioned tubular endosome (arrowhead) is also at the spine origin, near a thinner cross-section of SER (∗). Inset, A small vesicle adjacent to the plasmalemma in a spine head. Scale bar, 0.5 μm.