Induction of glutamate binding sites in hippocampal membranes by transient exposure to high concentrations of glutamate or glutamate analogs
Open Access
- 1 February 1986
- journal article
- research article
- Published by Society for Neuroscience in Journal of Neuroscience
- Vol. 6 (2), 355-363
- https://doi.org/10.1523/jneurosci.06-02-00355.1986
Abstract
The number of Na+-independent, Cl--dependent glutamate binding sites in rat hippocampal membranes is increased two- to fourfold after pre- exposing isolated membranes or hippocampal slices to high concentrations (0.1–10 mM) of L-glutamate or of glutamate analogs with high affinity for this binding site, such as quisqualate, homocysteate, or aminoadipate. N-Methylaspartate and kainate are ineffective. A similar binding increase is induced by transient exposure to the dipeptide tyrosylglutamate. The newly induced binding sites appear to be identical with pre-existing Cl--dependent binding sites by several criteria: They have a similar pharmacological profile, they are sensitive to low concentrations of Na+, and the number of sites can be further increased by transient exposure to micromolar calcium concentrations. Moreover, binding of [3H]APB, a ligand selective for the Cl--dependent glutamate binding sites, is also increased after glutamate preincubation. The induction of binding sites by high glutamate concentrations, described herein, is calcium-independent, not inhibited by leupeptin and, therefore, different from the previously described activation of binding sites by a calcium-sensitive protease. The high concentration of ligand needed to induce increased binding suggests the presence in hippocampal membranes of a binding site with low, millimolar affinity that is functionally related to the known high- affinity binding sites. Several interpretations of the observed effects and their implications for the possible relationship between the binding site and the synaptic receptor are discussed.This publication has 15 references indexed in Scilit:
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