Extracellular application of the N-methyl-D-aspartate receptor allosteric modulator rapastinel acts remotely to regulate Ca2+inactivation at an intracellular locus

Xiao Lei Zhang, Nils A. Berglund, Jeffrey S. Burgdorf, John E. Donello, Joseph R. Moskal, Patric K. Stanton*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Background A novel N-methyl-D-aspartate receptor (NMDAR) allosteric modulator, rapastinel (RAP, formerly GLYX-13), elicits long-lasting antidepressant-like effects by enhancing long-term potentiation (LTP) of synaptic transmission. RAP elicits these effects by binding to a unique site in the extracellular region of the NMDAR complex, transiently enhancing NMDAR-gated current in pyramidal neurons of both hippocampus and medial prefrontal cortex. Methods We compared efficacy of RAP in modulating Schaffer collateral-evoked NMDAR-currents as a function of kinetics of the Ca2+chelator in the intracellular solution, using whole-cell patch-clamp recordings. The intracellular solution contained either the slow Ca2+chelator EGTA [3,12-bis(carboxymethyl)-6,9-dioxa-3,12-diazatetradecane-1,14-dioic acid, 0.5 mmol/l] or the 40-500-fold kinetically faster, more selective Ca2+chelator BAPTA {2,2′,2″,2‴-[ethane-1,2-diylbis(oxy-2,1-phenylenenitrilo)] tetraacetic acid, 5 mmol/l}. NMDAR-gated currents were pharmacologically isolated by bath application of the 2-amino-3-(3-hydroxy-5-methyl-isoxazol-4-yl)propanoic acid receptor antagonist 6-nitro-2,3-dioxo-1,2,3,4-tetrahydrobenzo[f]quinoxaline-7-sulfonamide (10 μmol/l) plus the GABA receptor blocker bicuculline (20 μmol/l). Results When the slow Ca2+chelator EGTA was in the intracellular solution, RAP elicited significant enhancement of NMDAR-gated current at a 1 μmol/l concentration, and significantly reduced current at 10 μmol/l. In contrast, when recording with the 40-500-fold kinetically faster, more selective Ca2+chelator BAPTA, NMDAR current increased in magnitude by 84% as BAPTA washed into the cell, and the enhancement of NMDAR current by 1 μmol/l RAP was completely blocked. Interestingly, the reduction in NMDAR current from 10 μmol/l RAP was not affected by the presence of BAPTA in the recording pipette, indicating that this effect is mediated by a different mechanism. Conclusion Extracellular binding of RAP to the NMDAR produces a novel, long-range reduction in affinity of the Ca2+inactivation site on the NMDAR C-terminus accessible to the intracellular space. This action underlies enhancement in NMDAR-gated conductance elicited by RAP.

Original languageEnglish (US)
Pages (from-to)312-319
Number of pages8
JournalNeuroreport
Volume33
Issue number7
DOIs
StatePublished - May 4 2022

Keywords

  • CA1
  • N-methyl-D-aspartate receptor
  • Schaffer collateral
  • calcium
  • hippocampus
  • intracellular

ASJC Scopus subject areas

  • Neuroscience(all)

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