Receptor localization

Abstract

The distribution of acetylcholine receptor (AChR) subunit-like immunoreactivities (LI) on the surface of chick ciliary ganglion neurons was examined by indirect immunofluorescence and a laser scanning confocal microscope. AChRs were immunolabeled with rat or mouse antiAChR mAbs provided by Dr. Jon Lindstrom (UPenn) and Dr. Darwin Berg (UCSD). Synaptic sites were visualized with a mouse anti-SV2 mAb provided by Dr. Steve Carlson (UWash). Bound primary mAbs were visualized with secondary Abs conjugated with cyanine 3.18 or cyanine 5.18. Intracellular staining was noted in all neurons with antibodies specific for each of the subunits known to be expressed by the ganglion as a whole (α3, α5, α7, β2, β4). At At the neuronal surface α5-LI was distributed both at synaptic and extrasynaptic sites, while α7-LI was distributed exclusively at extrasynaptic sites. These results are consistent with previous electron microscopic observations of Jacob and Berg (J. Neurosci. 3: 260–271, 1983) and Jacob et al. (PNAS 81: 3223–3227, 1984). A5-α7 dual labeling showed some areas of co-localization and others areas where each subunit LI was present in the absence of the other. Rhodamine-a-bungarotoxin co-localized precisely with anti-α7 mAbs, in keeping with its documented ability to block α7 function. In initial trials none of the available mAbs specific for α3,ß2, or ß4 produced cell-surface staining. (Supported by NIH NS 24207.)