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Dynamics of the readily releasable pool during post‐tetanic potentiation in the rat calyx of Held synapse
Author(s) -
Habets Ron L. P.,
Borst J. Gerard G.
Publication year - 2007
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.2006.127365
Subject(s) - long term potentiation , excitatory postsynaptic potential , post tetanic potentiation , calyx , chemistry , time constant , synapse , biophysics , tetanic stimulation , postsynaptic potential , tetanus , neuromuscular junction , neuroscience , inhibitory postsynaptic potential , anatomy , biology , biochemistry , immunology , receptor , vaccination , electrical engineering , engineering
The size of the readily releasable pool (RRP) of vesicles was measured in control conditions and during post‐tetanic potentiation (PTP) in a large glutamatergic terminal called the calyx of Held. We measured excitatory postsynaptic currents evoked by a high frequency train of action potentials in slices of 4–11‐day‐old rats. After a tetanus the cumulative release during such a train was enlarged by approximately 50%, indicating that the size of the RRP was increased. The amount of enhancement depended on the duration and frequency of the tetanus and on the age of the rat. After the tetanus, the size of the RRP decayed more slowly ( t 1/2 = 10 versus 3 min) back to control values than the release probability. This difference was mainly due to a very fast initial decay of the release probability, which had a time constant compatible with an augmentation phase (τ≈ 30 s). The overall decay of PTP at physiological temperature was not different from room temperature, but the increase in release probability ( P r ) was restricted to the first minute after the tetanus. Thereafter PTP was dominated by an increase in the size of the RRP. We conclude that due to the short lifetime of the increase in release probability, the contribution of the increase in RRP size during post‐tetanic potentiation is more significant at physiological temperature.