Abstract
Acetylcholinesterase (ACNE) density at the neuromuscular junction of frog cutaneous pectoris muscle was determined by electron microscope autoradiography and biochemistry to be t600 sites μm-2 of postsynaptic area,t4-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 ACNE 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 ∼400 sites μm-2 and a turnover number of only ∼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 μm-2 and 16,000 s-1, respectively.
| Original language | English |
|---|---|
| Pages (from-to) | 783-794 |
| Number of pages | 12 |
| Journal | Neuron |
| Volume | 12 |
| Issue number | 4 |
| DOIs | |
| State | Published - Apr 1994 |
Bibliographical note
Funding Information:We thank Rachel Cohen and Maria Szabo for excellent technical assistance, Tom Bartol, Tom Podleski, and Ed Salpeter for useful discussion, and Debbie Moslehi for preparing the manuscript. This work was supported by NIH NS09315 and GM10422 (M. M. S.), NIH fellowship NSO9126(1. R. S.), US-Israel Binational Science Foundation grant BSF89-00502 (L. A. and M. M. S.), and the Bruno Goldberg Endowment Fund (L. A.). Computer simulations were conducted at the Cornell National Supercomputer Facility, a resource of the Center for Theory and Simulation Science and Engineering, Cornell University, Ithaca, NY.