Jo. Malva et al., A FUNCTIONALLY ACTIVE PRESYNAPTIC HIGH-AFFINITY KAINATE RECEPTOR IN THE RAT HIPPOCAMPAL CA3 SUBREGION, Neuroscience letters, 185(2), 1995, pp. 83-86
We studied the modulation of the intracellular free calcium concentrat
ions ([Ca2+](i)) by kainate/AMPA receptor activation in synaptosomes i
solated from whole rat hippocampus, or from its CA1, CA3 or dentate gy
rus subregions. The receptor was activated either by 100 mu M alpha-am
ino-3-hydroxy-5-methyl-4-isoxazolpropionic acid (AMPA) (EC(50) = 26.6
+/- 4.9 mu M) or by 100 mu M kainate (EC(50) = 0.81 +/- 0.1 mu M), but
the effects of these agonists were not additive. The response to eith
er AMPA or kainate was competitively inhibited by 10 mu M 6-cyano-7-ni
troquinoxaline-2,3-dioxine. Higher [Ca2+](i) responses to 100 mu M AMP
A or to 100 mu M kainate were observed in the CA3 subregion (43.2 +/-
2.5 nM or 42.8 +/- 2.3 nM, respectively) than in the whole hippocampus
(22.4 +/- 1.1 nM or 22.4 +/- 1.6, respectively), in the CA1 subregion
(26.4 +/- 1.1 nM or 26.6 +/- 2.6 nM, respectively) or in dentate gyru
s (24.6 +/- 1.4 nM or 21.5 +/- 1.0 nM, respectively). These results in
dicate that the CA3 subregion of the hippocampus is enriched in a pres
ynaptic high-affinity kainate receptor which modulates the [Ca2+](i) i
n nerve terminals.