Shal, but not Shaker, channels mediate theIA in the neuropil. Shown are horizontal optical sections from various STG whole-mount preparations stained with anti-Shal (A–F) and anti-Shaker (G), or an anti-Shaker-stained cross-section of the STG (H). A, An optical section from the center of the ganglion showing the peripheral zone (somata) encircling the layer of fine neuropil, which surrounds the coarse neuropil. Note that large processes are outlined in the central coarse neuropil and that tufts of fine neuropil along the periphery are intensely stained. The thickness of the slice is ∼13.3 μm.B, Higher magnification of the coarse neuropil showing a primary neurite with intense cytoplasmic staining, and higher order neurites with variations in the staining of the cytoplasm and the membrane. The slice thickness is ∼6.3 μm. C, High magnification of a neurite from the coarse neuropil;arrowheads point to presumptive glial somata or blood vessels adjacent to the neurite. The thickness of the slice is ∼1 μm. D, Projection of six optical sections, spanning ∼6–8 μm in depth, showing the variation in membrane staining intensity in neighboring neurites. Also note the lack of glial staining between neurites and the lack of glial somata. E, Optical cross-sectional view through the neuropil of a ganglion. Tracts of glia and large neurites separate the fine neuropil. Note that the anti-Shal stain encircles small fibers in the V-shaped regions of synaptic neuropil. Larger processes separating the fine neuropil are also outlined and some show cytoplasmic staining. The slice is ∼6.3-μm-thick. F, High magnification of the fine neuropil; note the amorphous mesh-like structure of this anti-Shal stained region. The section is 1–2 μm in depth.G, Optical section from the center of a whole-mount anti-Shaker-stained ganglion. Note the complete absence of staining in the neuropil. The thickness of the section is ∼13.3 μm.H, Cross-section from an anti-Shaker-stained ganglion. The thickness of the optical section is 6–8 μm. Note that the most intensely stained structure is the perineural sheath along the sides and bottom of the ganglion.
