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Kainate receptor‐mediated inhibition of presynaptic Ca 2+ influx and EPSP in area CA1 of the rat hippocampus
Author(s) -
Kamiya Haruyuki,
Ozawa Seiji
Publication year - 1998
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.1469-7793.1998.833bm.x
Subject(s) - excitatory postsynaptic potential , kainate receptor , ampa receptor , inhibitory postsynaptic potential , kainic acid , postsynaptic potential , chemistry , neurotransmission , nmda receptor , neuroscience , schaffer collateral , postsynaptic current , biophysics , glutamate receptor , biology , receptor , biochemistry
1 The effect of a low concentration (1 μM) of kainate (kainic acid; KA) on presynaptic calcium (Ca 2+ ) influx at the Schaffer collateral‐commissural (SCC) synapse was examined in rat hippocampal slices. 2 Following selective loading of the presynaptic terminals with the fluorescent Ca 2+ indicator rhod‐2 AM, transient increases in the presynaptic Ca 2+ concentration (pre[Ca 2+ ] t ) and field excitatory postsynaptic potentials (EPSPs) evoked by electrical stimulation of the SCC pathway were recorded simultaneously. 3 Bath application of 1 μM KA reversibly suppressed field EPSPs and pre[Ca 2+ ] t to 37.7 ± 4.0 % and 72.9 ± 2.4 % of control, respectively. Excitatory postsynaptic currents (EPSCs) recorded with the use of the whole‐cell patch‐clamp technique were also suppressed by 1 μM KA to 42.6 ± 6.3 % of control. A quantitative analysis of the decreases in pre[Ca 2+ ] t and the amplitude of field EPSP during KA application suggests that KA inhibits transmission primarily by reducing the pre[Ca 2+ ] t . 4 Consistent with a presynaptic site for these effects, paired‐pulse facilitation (PPF) was enhanced by 1 μM KA. 5 A substantial KA‐induced suppression of NMDA receptor‐mediated EPSPs was detected when AMPA receptors were blocked by the AMPA receptor‐selective antagonist GYKI 52466 (100 μM). 6 The suppressive effect of KA on field EPSPs and pre[Ca 2+ ] t was antagonized by the KA antagonist NS‐102 (10 μM). 7 These results suggest that the presynaptic inhibitory action of KA at the hippocampal CA1 synapse is primarily due to the inhibition of Ca 2+ influx into the presynaptic terminals.