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Kinetics, Ca2+ dependence, and biophysical properties of integrin-mediated mechanical modulation of transmitter release from frog motor nerve terminalsNeurotransmitter release from frog motor nerve terminals is strongly modulated by change in muscle length. Over the physiological range, there is an approximately 10% increase in spontaneous and evoked release per 1% muscle stretch. Because many muscle fibers do not receive suprathreshold synaptic inputs at rest length, this stretch-induced enhancement of release constitutes a strong peripheral amplifier of the spinal stretch reflex. The stretch modulation of release is inhibited by peptides that block integrin binding of natural ligands. The modulation varies linearly with length, with a delay of no more than approximately 1-2 msec and is maintained constant at the new length. Moreover, the stretch modulation persists in a zero Ca2+ Ringer and, hence, is not dependent on Ca2+ influx through stretch activated channels. Eliminating transmembrane Ca2+ gradients and buffering intraterminal Ca2+ to approximately normal resting levels does not eliminate the modulation, suggesting that it is not the result of release of Ca2+ from internal stores. Finally, changes in temperature have no detectable effect on the kinetics of stretch-induced changes in endplate potential (EPP) amplitude or miniature EPP (mEPP) frequency. We conclude, therefore, that stretch does not act via second messenger pathways or a chemical modification of molecules involved in the release pathway. Instead, there is direct mechanical modulation of release. We postulate that tension on integrins in the presynaptic membrane is transduced mechanically into changes in the position or conformation of one or more molecules involved in neurotransmitter release, altering sensitivity to Ca2+ or the equilibrium for a critical reaction leading to vesicle fusion.
Document ID
Document Type
Reprint (Version printed in journal)
Chen, B. M. (Jerry Lewis Neuromuscular Research Center, University of California Los Angeles School of Medicine 90095 United States)
Grinnell, A. D.
Date Acquired
August 22, 2013
Publication Date
February 1, 1997
Publication Information
Publication: The Journal of neuroscience : the official journal of the Society for Neuroscience
Volume: 17
Issue: 3
ISSN: 0270-6474
Subject Category
Life Sciences (General)
Distribution Limits
Non-NASA Center
NASA Discipline Cell Biology