Fig. 5.

Ultrastructural evidence for local endocytosis and exocytosis in the spine heads. a, Coated vesicle invaginating the plasma membrane of a spine head located away from the vicinity of the PSD. b, Membrane delimited MVB associated with the spine apparatus in the spine head.c, Smooth vesicle in the spine head adjacent to the plasma membrane. d, Smooth vesicle fusing with the plasma membrane of the spine head. (This image is somewhat soft because of enlargement from the side of a negative that was part of a longer series.) Scale bar (shown in d): 1.0 μm.