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Sequence dependence of post‐tetanic potentiation after sequential heterosynaptic stimulation in the rat auditory cortex
Author(s) -
Seki Kenjiro,
Kudoh Masaharu,
Shibuki Katsuei
Publication year - 2001
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 - 10.1111/j.1469-7793.2001.0503a.x
Subject(s) - long term potentiation , tetanic stimulation , muscarinic acetylcholine receptor , antagonist , muscarinic antagonist , bicuculline , pirenzepine , chemistry , neuroscience , excitatory postsynaptic potential , methoctramine , stimulation , postsynaptic potential , gabaa receptor , receptor , medicine , biology , biochemistry
To investigate the mechanisms for the coding stimulus sequence in the auditory cortex (AC), post‐tetanic potentiation (PTP) was recorded after sequentially combined heterosynaptic stimulation was applied in rat AC slices. Brief tetanic stimulation (TS) was applied at two sites on AC slices at intervals of 0.5–10 s. PTP of field potentials was induced by the earlier TS, rather than the later TS. PTP was followed by sequence‐dependent long‐term potentiation (LTP). Using Ca 2+ imaging in the slices loaded with rhod‐2, a Ca 2+ indicator, a sequence‐dependent distribution of PTP was found in AC slices. The sequence‐dependent PTP in excitatory postsynaptic potentials (EPSPs) was observed in supragranular pyramidal neurons. The sequence dependence of PTP was not significantly affected by 1 μ m bicuculline, an antagonist of GABA A receptors, or 100 μ m 2‐hydroxysaclofen, an antagonist of GABA B receptors. Depolarization and firing recorded in pyramidal neurons during the later TS were less vigorous than when the slices were incubated in the control medium. However, this suppression of the responses during the later TS was not observed in the presence of 50 μ m atropine, an antagonist of muscarinic receptors. PTP was induced by the earlier and later TS in the presence of 50 μ m atropine, so that the sequence dependence of PTP was abolished. Pirenzepine (50 μ m ), an antagonist of muscarinic M1 receptors, but not methoctramine (30 μ m ), an antagonist of M2 receptors, eliminated the sequence dependence of PTP. These findings suggest that the sequence dependence of PTP in AC might have a role in the temporal processing of auditory information on the scale of seconds.