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Differential responses to NMDA receptor activation in rat hippocampal interneurons and pyramidal cells may underlie enhanced pyramidal cell vulnerability
Author(s) -
Avig E.,
Frenguelli B. G.,
Irving A. J.
Publication year - 2005
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1111/j.1460-9568.2005.04497.x
Subject(s) - nmda receptor , neuroscience , pyramidal cell , hippocampal formation , excitotoxicity , chemistry , patch clamp , excitatory postsynaptic potential , biology , electrophysiology , receptor , inhibitory postsynaptic potential , biochemistry
Hippocampal interneurons are generally more resistant than pyramidal cells to excitotoxic insults. Because NMDA receptors play a crucial role in neurodegeneration, we have compared the response to exogenous NMDA in CA1 pyramidal cells and interneurons of the stratum oriens using combined whole‐cell patch‐clamp recording and ratiometric Ca 2+ imaging. In voltage‐clamp, current‐clamp or in nominally Mg 2+ ‐free medium, NMDA (10 µ m ; 3–5 min exposure in the presence of tetrodotoxin) induced a markedly larger inward current and Ca 2+ rise in pyramidal cells than in interneurons. Pyramidal cells also showed a more pronounced voltage dependence in their response to NMDA. We hypothesized that this enhanced response to NMDA receptor activation in pyramidal cells could underlie their increased vulnerability to excitotoxicity. Using loss of dye as an indicator of degenerative membrane disruption, interneurons tolerated continuous exposure to a high concentration of NMDA (30 µ m ) for longer periods than pyramidal cells. This acute neurodegeneration in pyramidal cells was independent of intracellular Ca 2+ , because high intracellular BAPTA (20 m m ) did not prolong survival time. Thus, a plausible explanation for the enhanced sensitivity of pyramidal neurons to excitotoxic insults associated with cerebral ischemia is their greater response to NMDA receptor activation, which may reflect differences in NMDA receptor expression and/or subunit composition.