Journal of Neuroscience, Vol 3, 2395-2402, Copyright © 1983 by Society for Neuroscience
Differential regulation of acetylcholine sensitivity and alpha- bungarotoxin-binding sites on ciliary ganglion neurons in cell culture
MA Smith, JF Margiotta and DK Berg
Levels of acetylcholine (ACh) sensitivity and numbers of alpha-
bungarotoxin (alpha-Bgt)-binding sites have been measured for chick ciliary
ganglion neurons grown in cell culture under various conditions. The two
properties were found not to change in parallel. Neurons maintained in
culture medium supplemented with embryonic eye extract developed high
levels of ACh sensitivity and low numbers of alpha-Bgt-binding sites,
whereas neurons grown in medium containing elevated K+ concentrations
displayed the reverse. Neurons from media containing both eye extract and
elevated K+ concentrations had both low levels of sensitivity and low
numbers of toxin sites. The growth conditions do not alter the basic
binding properties of the ACh receptors and alpha-Bgt-binding sites. Both
the ACh receptor dose- response characteristics and the pharmacological
properties of the toxin-binding sites were similar for neurons grown in
media containing eye extract or elevated K+ concentrations. The inhibitory
effects of eye extract on development of alpha-Bgt-binding sites appeared
to be specific: eye extract had previously been shown to stimulate neuronal
growth and cholinergic development, and in the present study eye extract
enhanced development of ACh sensitivity and had no effect on mechanisms
responsible for binding and accumulation of tetanus toxin. Eye extract did
not block alpha-Bgt binding in competition binding experiments and did not
cause redistribution of toxin sites away from the neuronal soma. These
results demonstrate that ACh sensitivity and alpha-Bgt-binding sites can be
independently regulated on the neurons and suggest that the two membrane
properties are associated with separate membrane components.
