Abstract
We have examined the variation in receptor density and area among neurite-associated acetylcholine receptor patches (NARPs) induced by chick ciliary ganglion neurons on nearby myotubes in vitro. Quantitative analysis of rhodamine-α-bungarotoxin (RBTX) NARPs revealed that about 15% of the NARPs were "outstanding" in terms of size (>60 μm2) and fluorescence intensity (>100 units on a 0-255 scale). The total number of receptors at different NARPs ranged over 3 orders of magnitude. It is likely that variation in NARP size and intensity reflects regional variation in the ability of myotubes to respond to the neuronal influence because (1) no gradient in NARP size or intensity with distance from the soma was evident; (2) the intensities and areas of uninnervated receptor clusters (hot spots) were similar to those of NARPs; (3) acetylcholinesterase was present at the same proportion of hot spots and NARPs at all times examined. We found no physiological or morphological evidence that outstanding NARPs were more effective sites of transmitter release. Outstanding NARPs were restricted to the longest neurite of individual neurons, so they may signal trophic interactions of the sort that promote neurite outgrowth and survival.
Original language | English (US) |
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Pages (from-to) | 209-219 |
Number of pages | 11 |
Journal | Developmental Biology |
Volume | 130 |
Issue number | 1 |
DOIs | |
State | Published - Nov 1988 |
Bibliographical note
Funding Information:The authors are indebted to Mr. Jim Voyvodic and Mr. Viken Ma-tossian for developing the software for manipulation of the video images. We thank Dr. Joe Henry Steinbach for helpful discussions, Dr. Lorna Role who took part in the initial experiments, and Dr. Paul Bridgman for assistance in preparing RBTX. This work was supported by grants from the NIH (NS 18458; G.D.F.); NS 22828, A National Science Foundation Predoctoral Fellowship (M.M.), A Muscular Dystrophy Association Postdoctoral Fellowship (J.D.) and the Washington University Center for Cellular and Molecular Neurobiology.