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Transmitter release from normal and degenerating locust motor nerve terminals.
Author(s) -
Hodgkiss J P,
Usherwood P N
Publication year - 1978
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1978.sp012561
Subject(s) - excitatory postsynaptic potential , motor nerve , locust , axon , neuromuscular junction , transmitter , anatomy , coupling (piping) , electrophysiology , chemistry , biophysics , neuroscience , biology , materials science , inhibitory postsynaptic potential , telecommunications , channel (broadcasting) , botany , computer science , metallurgy
1. An analysis has been made of spontaneous and evoked transmitter release from terminals of 'fast' excitatory motor axons on locust muscle fibres using intra‐ and extracellular recording together with a Ca‐electrode technique for activating transmitter release from single nerve terminals on multiterminally innervated muscle fibres. 2. Spontaneous intracellular miniature excitatory junction potentials (m.e.j.p.s), recorded at active spots on these muscle fibres, occurred non‐randomly with frequent bursts of m.e.j.p.s. 3. M.e.j.p.s of subnormal amplitude were also seen but contributed only a small fraction of the minature discharge. 4. The amplitude distribution of intracellularly recorded excitatory junction potentials (e.j.p.s) evoked during ionophoretic application of Ca onto single nerve terminals was adequately predicted by Poisson statistics. 5. During the course of nerve terminal degeneration m.e.j.p.s of subnormal amplitude became more frequent and eventually formed the major part of the miniature discharge. Transmitter quanta responsible for 'small' m.e.j.p.s did not contribute to evoked release either at normal or degenerating terminals. Evoked transmitter release from degenerating axon terminals before excitation‐secretion coupling failure conformed to Poisson statistics. 6. It is concluded that more than one release mechanism operates on the transmitter pool or pools in locust motor nerve terminals.