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Augmentation by glycine and blockade by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) of responses to excitatory amino acids in slices of rat neocortex.
Neuroscience. 1990; 39(1):69-79.N

Abstract

Responses of neocortical pyramidal cells to excitatory amino acids were recorded intracellularly. Agonists and antagonists were applied electrophoretically from a separate multibarrel pipette and care taken to ensure that the pipette was positioned to evoke optimal responses to N-methyl-D-aspartate (NMDA), or homocysteic acid, before control responses were recorded. Responses to NMDA, but not those to alpha-amino-3-hydroxy-5-methyl-4-isoxazdepropionic acid (AMPA) or quisqualate, were enhanced when glycine was co-applied. Responses to AMPA, quisqualate and NMDA were reduced by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) applied either electrophoretically, or in the bathing medium, with responses to quisqualate being the least and those to AMPA being the most sensitive to CNQX. The blockade of NMDA responses by CNQX was selectively reversed by additional glycine confirming that CNQX blocks NMDA receptor-channel complexes at the glycine, rather than at the NMDA site. Under control conditions, responses to glutamate resembled responses to quisqualate, and were relatively insensitive to CNQX, 3-((+/-)-2-carboxypiperazin-4-yl)-propyl-l-phosphonic acid and 2-amino-5-phosphonovalerate, while responses to homocysteic acid resembled responses to NMDA and were blocked by these antagonists. This suggested that homocysteic acid acted at NMDA receptors, while glutamate acted primarily at non-NMDA receptors. However, responses to both glutamate and homocysteic acid were augmented by additional glycine when these transmitter candidates were applied close to a "hot spot" for NMDA receptor activation. The glycine enhancement of responses to glutamate was sensitive to NMDA antagonists, indicating that glutamate can activate NMDA receptors in an intact preparation if glycine levels are high enough.

Authors+Show Affiliations

Department of Physiology, Royal Free Hospital School of Medicine, London, U.K.

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

1982468

Citation

Thomson, A M.. "Augmentation By Glycine and Blockade By 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) of Responses to Excitatory Amino Acids in Slices of Rat Neocortex." Neuroscience, vol. 39, no. 1, 1990, pp. 69-79.
Thomson AM. Augmentation by glycine and blockade by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) of responses to excitatory amino acids in slices of rat neocortex. Neuroscience. 1990;39(1):69-79.
Thomson, A. M. (1990). Augmentation by glycine and blockade by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) of responses to excitatory amino acids in slices of rat neocortex. Neuroscience, 39(1), 69-79.
Thomson AM. Augmentation By Glycine and Blockade By 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) of Responses to Excitatory Amino Acids in Slices of Rat Neocortex. Neuroscience. 1990;39(1):69-79. PubMed PMID: 1982468.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Augmentation by glycine and blockade by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) of responses to excitatory amino acids in slices of rat neocortex. A1 - Thomson,A M, PY - 1990/1/1/pubmed PY - 1990/1/1/medline PY - 1990/1/1/entrez SP - 69 EP - 79 JF - Neuroscience JO - Neuroscience VL - 39 IS - 1 N2 - Responses of neocortical pyramidal cells to excitatory amino acids were recorded intracellularly. Agonists and antagonists were applied electrophoretically from a separate multibarrel pipette and care taken to ensure that the pipette was positioned to evoke optimal responses to N-methyl-D-aspartate (NMDA), or homocysteic acid, before control responses were recorded. Responses to NMDA, but not those to alpha-amino-3-hydroxy-5-methyl-4-isoxazdepropionic acid (AMPA) or quisqualate, were enhanced when glycine was co-applied. Responses to AMPA, quisqualate and NMDA were reduced by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) applied either electrophoretically, or in the bathing medium, with responses to quisqualate being the least and those to AMPA being the most sensitive to CNQX. The blockade of NMDA responses by CNQX was selectively reversed by additional glycine confirming that CNQX blocks NMDA receptor-channel complexes at the glycine, rather than at the NMDA site. Under control conditions, responses to glutamate resembled responses to quisqualate, and were relatively insensitive to CNQX, 3-((+/-)-2-carboxypiperazin-4-yl)-propyl-l-phosphonic acid and 2-amino-5-phosphonovalerate, while responses to homocysteic acid resembled responses to NMDA and were blocked by these antagonists. This suggested that homocysteic acid acted at NMDA receptors, while glutamate acted primarily at non-NMDA receptors. However, responses to both glutamate and homocysteic acid were augmented by additional glycine when these transmitter candidates were applied close to a "hot spot" for NMDA receptor activation. The glycine enhancement of responses to glutamate was sensitive to NMDA antagonists, indicating that glutamate can activate NMDA receptors in an intact preparation if glycine levels are high enough. SN - 0306-4522 UR - https://www.unboundmedicine.com/medline/citation/1982468/Augmentation_by_glycine_and_blockade_by_6_cyano_7_nitroquinoxaline_23_dione__CNQX__of_responses_to_excitatory_amino_acids_in_slices_of_rat_neocortex_ DB - PRIME DP - Unbound Medicine ER -