Localization of individual calcium channels at the release face of a presynaptic nerve terminal

Abstract

<p>Studies using biophysical techniques suggest a highly structured organization of <a href="http://topics.sciencedirect.com/topics/page/Calcium_channel">calcium channels</a> at the <a href="http://topics.sciencedirect.com/topics/page/Chemical_synapse">presynaptic</a> transmitter release face (<a href="http://www.sciencedirect.com/science/article/pii/0896627394904146#bib17" id="x-x-ancbbib17">Llinás et al., 1981</a>; <a href="http://www.sciencedirect.com/science/article/pii/0896627394904146#bib36" id="x-x-ancbbib36">Stanley, 1993</a>), but it has not as yet proved possible to localize identified channels at the required nanometer level of resolution. We have used atomic force microscopy on the calyx-type nerve terminal of the chick <a href="http://topics.sciencedirect.com/topics/page/Ciliary_ganglion">ciliary ganglion</a> to localize single calcium channels tagged via biotinylated ω-conotoxin GVIA to avidin-coated 30 nm gold particles. Calcium channels were in low (modal value approximately ⩽ 1 per μm²) and high (modal value55 per μm²) density areas and exhibited a prominent interchannel spacing of 40 nm, indicating an intermolecular linkage. Particles were observed in clusters and short linear or parallel linear arrays, groupings that may reflect <a href="http://topics.sciencedirect.com/topics/page/Calcium_channel">calcium channel</a> organization at the transmitter release site.</p>