Premium
Fractional Ca2+ currents through somatic and dendritic glutamate receptor channels of rat hippocampal CA1 pyramidal neurones.
Author(s) -
Garaschuk O,
Schneggenburger R,
Schirra C,
Tempia F,
Konnerth A
Publication year - 1996
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.1996.sp021255
Subject(s) - ampa receptor , nmda receptor , kainate receptor , glutamate receptor , biophysics , chemistry , hippocampal formation , receptor , biology , microbiology and biotechnology , neuroscience , biochemistry
1. The Ca2+ permeability of non‐NMDA and NMDA receptor channels was studied using a fluorometric flux measurement approach in somata and dendrites of CA1 pyramidal neurones in rat hippocampal slices. For this purpose, the Ca2+ fraction of the total cation current (named ‘fractional Ca2+ current') was measured directly from the change in the Ca(2+)‐sensitive fura‐2 fluorescence at 380 nm excitation wavelength. 2. The fractional Ca2+ current through the somatic NMDA receptor channels was 10.69 +/‐ 2.13% (mean +/‐ S.D.) and that through dendritic receptor channels was 10.70 +/‐ 1.96%. The fractional Ca2+ current was not dependent on the extracellular Mg2+ concentration and its voltage dependence was in agreement with the Goldman‐Hodgkin‐Katz current equation. 3. AMPA (alpha‐amino‐3‐hydroxy‐5‐methylisoxazole‐4‐propionate) or kainate applications produced small but significant Ca2+ entry. Fractional Ca2+ currents of 0.58 +/‐ 0.34% were measured for somatic AMPA applications, 0.68 +/‐ 0.20% for somatic kainate applications, 0.66 +/‐ 0.25% for dendritic AMPA applications and 0.61 +/‐ 0.16% for dendritic kainate applications. 4. The expression pattern of glutamate receptor subunits encoding messenger ribonucleic acids (mRNAs) was analysed with the single‐cell reverse transcriptase‐polymerase chain reaction (RT‐PCR) approach applied to CA1 pyramidal neurones. The AMPA receptor subunits GluR‐A, GluR‐B and GluR‐C, and the NMDA receptor subunits NR2A and NR2B were found to be abundantly expressed in all CA1 pyramidal neurones tested. 5. This study establishes the fractional Ca2+ current through somatic and dendritic NMDA and non‐NMDA receptor channels in CA1 pyramidal neurones. The dendritic, presumably synaptic, NMDA receptor channels are highly Ca2+ permeable and have a fractional Ca2+ current closely resembling that of somatic extrasynaptic NMDA receptor channels. Both somatic and dendritic non‐NMDA receptor channels are of the ‘low Ca2+ permeable’ type and have a fractional Ca2+ current that is about twenty times smaller than that of NMDA receptor channels.