Figure 10. Gap junctions can be displayed
as transmission electron microscope (TEM) image density profiles for
homocellular (black lines) and heterocellular (dotted lines) pairings.
A central 12–13 nm wide pentalaminar zone with three sharp dense bands
representing membrane protein density is common to all retinal gap
junctions. But the flanking cytoplasmic compartments differ markedly.
Homocellular gap junctions between pairs of AII amacrine cells show
little protein density near the membrane. Conversely, heterocellular
gap junctions between AII amacrine cells and cone bipolar cells show
thick bands of protein density extending about 10 nm and over 15 nm
from the bipolar cell and amacrine cell faces, respectively.