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Complex binding of L-[3H]glutamate to hippocampal synaptic membranes in the absence of sodium.

Publication ,  Journal Article
Werling, LL; Nadler, JV
Published in: J Neurochem
April 1982

Specific binding of L-[3H]glutamate was investigated with a thoroughly washed synaptic membrane preparation from rat hippocampal formation, a region of brain densely innervated by putatively glutamatergic fibers. L-[3H]Glutamate bound rapidly, saturably, and reversibly to these membranes in the absence of Na+. Specific binding was greatest around 38 degrees C and at a slightly acidic pH. Saturation isotherms fit a model of two independent binding sites with dissociation constants of 11 and 570 nM and corresponding densities of 2.5 and 47 pmol/mg protein. All potent amino acid excitants, except N-methyl-D-aspartate and kainate, and several excitatory amino acid antagonists inhibited specific radioligand binding with IC50 values between 10(-7) M and 10(-4) M. In contrast, weak amino acid excitants and an inhibitor of glutamate uptake were nearly inactive. Displacement curves were analyzed with a computer program that assumed the simultaneous contributions of two independent sites at which each compound competitively inhibited the binding of L-[3H]glutamate. According to this analysis, ibotenate and the L- and D-isomers of glutamate and aspartate bind preferentially to the high-affinity site, whereas quisqualate, L-alpha-aminoadipate, and the L- and D-isomers of homocysteate bind preferentially to the low-affinity site. With the notable exception of gamma-D-glutamylglycine, all of the more potent antagonists appear to bind preferentially to the low-affinity site. Both sites exhibit marked stereoselectivity for L-glutamate. D- and L-Homocysteate and most excitatory amino acid antagonists increased specific binding at concentrations below those required to demonstrate inhibition. Some properties of the low-affinity binding site resemble those of junctional glutamate receptors on insect muscle, but neither site appears to correspond to the "N-methyl-D-aspartate receptor" or the "quisqualate receptor."

Duke Scholars

Published In

J Neurochem

DOI

ISSN

0022-3042

Publication Date

April 1982

Volume

38

Issue

4

Start / End Page

1050 / 1062

Location

England

Related Subject Headings

  • Synaptic Membranes
  • Structure-Activity Relationship
  • Sodium
  • Receptors, Neurotransmitter
  • Receptors, Glutamate
  • Receptors, Cell Surface
  • Rats, Inbred Strains
  • Rats
  • Neurology & Neurosurgery
  • Kinetics
 

Citation

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Werling, L. L., & Nadler, J. V. (1982). Complex binding of L-[3H]glutamate to hippocampal synaptic membranes in the absence of sodium. J Neurochem, 38(4), 1050–1062. https://doi.org/10.1111/j.1471-4159.1982.tb05347.x
Werling, L. L., and J. V. Nadler. “Complex binding of L-[3H]glutamate to hippocampal synaptic membranes in the absence of sodium.J Neurochem 38, no. 4 (April 1982): 1050–62. https://doi.org/10.1111/j.1471-4159.1982.tb05347.x.
Werling, L. L., and J. V. Nadler. “Complex binding of L-[3H]glutamate to hippocampal synaptic membranes in the absence of sodium.J Neurochem, vol. 38, no. 4, Apr. 1982, pp. 1050–62. Pubmed, doi:10.1111/j.1471-4159.1982.tb05347.x.
Werling LL, Nadler JV. Complex binding of L-[3H]glutamate to hippocampal synaptic membranes in the absence of sodium. J Neurochem. 1982 Apr;38(4):1050–1062.
Journal cover image

Published In

J Neurochem

DOI

ISSN

0022-3042

Publication Date

April 1982

Volume

38

Issue

4

Start / End Page

1050 / 1062

Location

England

Related Subject Headings

  • Synaptic Membranes
  • Structure-Activity Relationship
  • Sodium
  • Receptors, Neurotransmitter
  • Receptors, Glutamate
  • Receptors, Cell Surface
  • Rats, Inbred Strains
  • Rats
  • Neurology & Neurosurgery
  • Kinetics