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Long‐term potentiation of transmitter release induced by repetitive presynaptic activities in bull‐frog sympathetic ganglia.
Author(s) -
Koyano K,
Kuba K,
Minota S
Publication year - 1985
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.1985.sp015582
Subject(s) - long term potentiation , post tetanic potentiation , tetanic stimulation , excitatory postsynaptic potential , stimulation , chemistry , synaptic vesicle , electrophysiology , neuroscience , medicine , biology , endocrinology , anesthesia , biophysics , vesicle , inhibitory postsynaptic potential , biochemistry , receptor , membrane
Long‐lasting potentiation of transmitter release induced by repetitive presynaptic activities in bull‐frog sympathetic ganglia was studied by recording intracellularly fast excitatory post‐synaptic potentials (fast e.p.s.p.s.). Following a brief period of post‐tetanic potentiation or depression (less than 10 min), the amplitude of the fast e.p.s.p. was potentiated for a period between several tens of minutes and more than 2 h in response to tetanic stimulation of the preganglionic nerve in twenty‐one out of twenty‐eight cells. Quantal analysis revealed that this long‐term potentiation of the fast e.p.s.p. (l.t.p.) was accompanied by an increase in quantal content m (in nine out of twenty‐one cells), quantal size (four cells) or both (eight cells). The increased quantal content (presynaptic l.t.p.) declined exponentially (ten cells) or decayed gradually to a certain enhanced level which lasted several hours. In contrast, the increased quantal size grew with a relatively long latency (10‐25 min) and remained relatively constant for at least 2 h. The magnitude of presynaptic l.t.p. increased with increased duration of the presynaptic tetanus (33 Hz) from 2 to 5 s. No l.t.p. was elicited by a 1‐s tetanus, whereas the time course appears to be independent of the tetanus duration and the magnitude of l.t.p. There was a positive correlation between the magnitude of presynaptic l.t.p. and the pre‐tetanic quantal content up to m = 3, but the former deviated from linear regression when the value of the latter exceeded 3. No l.t.p. occurred when quantal content was less than 0.5. A tetanus (33 Hz, 10 s) applied in Ca2+‐free solution elicited no presynaptic l.t.p., while the same tetanus in normal Ringer solution produced a large presynaptic l.t.p. Presynaptic l.t.p. was enhanced in magnitude at low temperature (8‐10 degrees C). These results demonstrate the existence of a use‐dependent, long‐term potentiation of transmitter release in bull‐frog sympathetic ganglia. Several possible mechanisms are discussed in terms of Ca2+‐buffering mechanisms of the presynaptic nerve terminals.