Journal of Neuroscience, Vol 9, 3673-3680, Copyright © 1989 by Society for Neuroscience
Specific down-regulation of the alpha-bungarotoxin binding component on chick autonomic neurons by ciliary neuronotrophic factor
SW Halvorsen and DK Berg
Department of Biology, University of California, San Diego, La Jolla 92093.
Chick ciliary ganglion neurons have a cholinergic membrane component that
binds alpha-bungarotoxin with high affinity but has no known function. The
component is different from the nicotinic ACh receptor on the neurons that
mediates cholinergic transmission through the ganglion. Ciliary
neuronotrophic factor (CNTF) has been shown to enhance the survival of
ciliary ganglion neurons in cell culture and has been postulated to act as
a target-derived trophic factor for the neurons in vivo. We show here that
a factor indistinguishable from CNTF specifically down-regulates
alpha-bungarotoxin binding sites on the neurons while increasing cell
growth and the number of ACh receptors on the cells. Similar effects,
though reduced in magnitude, are seen with chick sympathetic neurons. CNTF
has no effect on the number of ACh receptors found on chick myotubes in
culture. The down-regulation of alpha-bungarotoxin binding sites on neurons
caused by CNTF occurs with a half-time of about 19 hr and is largely
reversed within a 4 d period following CNTF removal. It is distinct from
the down-regulation caused by cholinergic agonists. Nerve growth factor and
fibroblast growth factor have no apparent effect on the number of
alpha-bungarotoxin binding sites on the neurons, though fibroblast growth
factor does stimulate neuronal growth. The results indicate that the
effects of CNTF on the alpha-bungarotoxin binding component are both novel
for a growth factor and specific, and they suggest a relationship between
the component and the regulation of growth by the target tissue.
Previous Article | Next Article
