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Photolysis‐induced suppression of inhibition in rat hippocampal CA1 pyramidal neurons
Author(s) -
Wang Jun,
Zucker Robert S.
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.t01-1-00757.x
Subject(s) - depolarization , biophysics , chemistry , photodissociation , egta , membrane potential , patch clamp , postsynaptic potential , intracellular , calcium , biochemistry , photochemistry , receptor , biology , organic chemistry
1 Whole cell patch clamp recording, Ca 2+ measurement with ratiometric fluorescent dyes and photolysis of caged Ca 2+ were combined to investigate the depolarization‐ and photolysis‐induced suppression of inhibition (DSI and PSI) in rat hippocampal CA1 pyramidal cells. 2 A 5‐s depolarization from −70 mV to 0 mV or a 6‐s photolysis of nitrophenyl‐EGTA (NPE) in cell bodies could each depress the frequency of spontaneous inhibitory postsynaptic currents (IPSCs) and the amplitude of evoked IPSCs while elevating intracellular Ca 2+ concentration ([Ca 2+ ] i ). 3 Within a cell the elevation of [Ca 2+ ] i induced by depolarization was inversely related to that induced by photolysis, suggesting that higher [NPE] is more effective in releasing caged Ca 2+ but also increases buffer capacity to reduce [Ca 2+ ] i rises caused by Ca 2+ influx through voltage‐dependent Ca 2+ channels. 4 Both DSI and PSI were linearly related to [Ca 2+ ] i , with a 50 % reduction in transmission occurring at about 3.6‐3.9 μM. 5 [Ca 2+ ] i recovered more quickly than DSI, indicating that the duration of DSI is not set simply by the duration of [Ca 2+ ] i elevation, but rather entails other rate‐limiting processes. 6 We conclude that DSI is activated by micromolar [Ca 2+ ] i acting far from sites of Ca 2+ entry through channels in the plasma membrane.