Abstract
Acetylcholinesterase (AChE) density at the neuromuscular junction
of frog cutaneous pectoris muscle was determined by electron microscope
autoradiography and biochemistry to be approximately 600 sites micron-2
of postsynaptic area, approximately 4-fold lower than all previous
reports (mouse), whereas the hydrolytic turnover number was 9,500
s-1, well within the range (2,000-16,000 s-1) for AChE from other
species. Monte Carlo computer simulations of miniature endplate currents
showed that for vertebrate neuromuscular junctions with different
morphologies, an AChE density of only approximately 400 sites microns-2
and a turnover number of only approximately 1,000 s-1 are sufficient
for normal quantal currents. Above these critical lower limits, miniature
endplate currents were essentially insensitive to AChE density and
turnover number values up to 5,000 sites microns-2 and 16,000 s-1,
respectively.
- 8161450
- acetylcholine,
- acetylcholinesterase,
- animals,
- autoradiography,
- cholinergic,
- computer
- conductivity,
- electric
- electron,
- gov't,
- junction,
- microscopy,
- muscles,
- neuromuscular
- non-p.h.s.,
- non-u.s.
- p.h.s.,
- ranidae,
- receptors,
- research
- simulation,
- support,
- synapses,
- u.s.
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