ISSN:
1432-1106
Keywords:
Extracellular Na+ concentration
;
Quisqualate (quis)
;
N-methyl-D-aspartate (NMDA)
;
Tetrodotoxin (TTX)
;
Hippocampal area CA1
;
Rat
;
Extracellular Ca2+ concentration
;
Extracellular Mg2+ concentration
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary Decreases in extracellular sodium concentration ([Na+]o) and associated slow negative field potentials (fp's) were monitored with double barreled sodium sensitive/reference microelectrodes in area CA1 of rat hippocampal slices during iontophoretic application of the glutamate receptor agonists N-methyl-D-aspartate (NMDA) and quisqualate (quis). The effects of lowering [Ca2+]o on these signals were compared to those of lowering [Mg2+]o. Both NMDA- and quis-induced decreases in [Na+]o of up to 60 mM and in the fp's of up to 8 mV. Decreasing [Mg2+]o enhanced NMDA-induced signals, whereas quis-induced signals were unaffected. Lowering [Ca2+]o also enhanced NMDA signals, although somewhat less than lowering [Mg2+]o. This effect was still present, even when voltage dependent Na+ currents were blocked by 10-7 tetrodotoxin. Interestingly, quis-induced signals could be enhanced in a low Ca2+ medium as well, but only when high quis concentrations were used. The results suggest that, during the sorts of large decreases of [Ca2+]o observed during seizure activity, activation of NMDA receptors is facilitated.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00247502
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