Figure 2.

Morphology of contact sites between astrocytes and dendrites. a–e, Variable morphology of contact sites revealed by three-dimensional modeling of two-photon image stacks. Contact sites are either large enough to encircle the neck of dendritic protrusions (arrowhead in a; enlarged in d, e) or confined to a small area (arrow in a; enlarged in b, c). Higher-magnification views are from different angles (c and e are from the similar direction as in a, and views from different angles are in b and d). f, Three-dimensional reconstruction of electron microscopic images from the area CA1 of a slice culture (6 d in vitro) illustrating contacts between a dendritic protrusion (red) and an axon terminal (yellow) and also between a dendritic protrusion and an astrocytic process (green; f-2). A single micrograph containing the structure of a typical synaptic junction from the serial electron microscopic images is shown in f-1. g, A single electron microscopic image from the area CA1 of a slice culture (6 d in vitro) showing contacts between a dendritic protrusion (red) and an astrocytic process (green). Although three-dimensioal reconstruction analysis identified physical association of the dendritic protrusion with axonal components (yellow), no prominent synaptic junctions could be identified. Scale bars: a, 5 μm; f-1, g, 500 nm.