A Novel Allosteric Potentiator of AMPA Receptors: 4-[2-(Phenylsulfonylamino)ethylthio]-2,6-Difluoro-Phenoxyacetamide

Abstract

We report that a novel sulfonylamino compound, 4-[2-(phenylsulfonylamino)ethylthio]-2,6-difluoro-phenoxyacetamide (PEPA), selectively potentiates glutamate receptors of the AMPA subtype. PEPA (1-200 M) dose dependently potentiated glutamateevoked currents in Xenopus oocytes expressing AMPA (GluRAGluRD), but not kainate (GluR6 and GluR6ϩKA2) or NMDA (1 ϩ ⑀1-⑀4), receptor subunits. PEPA was effective at micromolar concentrations and, in contrast to the action of cyclothiazide, preferentially modulated AMPA receptor flop isoforms. At 200 M, PEPA potentiated glutamate responses by 50-fold in oocytes expressing GluRC flop (EC 50 ϳ50 M) versus only threefold for GluRC flip ; a similar preference for flop isoforms was observed for other AMPA receptor subunits. Dose-response analysis for GluRC flop revealed that 100 M PEPA produced a sevenfold increase in AMPA receptor affinity for glutamate. PEPA produced considerably weaker potentiation of kainate-evoked than glutamate-evoked currents, suggesting modulation of the process of receptor desensitization. In human embryonic kidney 293 cells transfected with AMPA receptor subunits, PEPA either abolished or markedly slowed the rate of onset of desensitization and potentiated steady-state equilibrium currents evoked by glutamate with subunit (GluRC Ն GluRD Ͼ GluRA) and splice-variant (flop Ͼ flip) selectivity similar to that observed in oocytes. Our results show that PEPA is a novel, flop-preferring allosteric modulator of AMPA receptor desensitization at least 100 times more potent than aniracetam. Key words: glutamate receptors; AMPA; desensitization; alternative splicing; flip and flop; allosteric modulationAllosteric modulation of the three subtypes of ionotropic glutamate receptors-AM PA, kainate, and NMDA receptors-is produced by a diverse spectrum of agents, including lectins, a variety of drugs, polyamines, and divalent cations. The unusually strong modulation of AM PA receptors by the benzothiadiazine and pyrrolidinone compounds cyclothiazide, aniracetam, and their derivatives (Ito et al

Heterogeneity in expression of functional ionotropic glutamate and GABA receptors in astrocytes across brain regions: insights from the thalamus

“…The cells were exposed to the AMPA/kainate receptor agonist, kainate (500 mM), supplemented with CTZ (100 mM) or PEPA (100 mM), which modulate AMPA receptors containing the flip or flop splice variants, respectively [11,38]. Prior to application of agonists and modulators, the large astrocytic Kir and leak conductances were blocked by BaCl 2 (100 mM) and quinine (200 mM), or BaCl 2 , TEA (10 mM) and 4-AP (4 mM) [33].…”

Pharmacological Discrimination of Extinction and Reconsolidation of Contextual Fear Memory by a Potentiator of AMPA Receptors

“…The facilitating action of PEPA on extinction can be explained by activation of the mPFC, which is one of the crucial factors in consolidation and retrieval of extinction (Milad and Quirk, 2002;Milad et al, 2004). A candidate molecular basis for the more potent electrophysiological activity of PEPA in the mPFC than in the BLA and CA1 is that the relative expression level of GluR3-flop mRNA, an AMPA receptor variant most vigorously potentiated by PEPA (Sekiguchi et al, 1997), is higher in the mPFC than in the BLA and CA1 (Zushida et al, 2007). The importance of the BLA in the reconsolidation of fear memory has been shown (Nader et al, 2000;Duvarci and Nader, 2004;Baldi et al, 2008), as mentioned in the Introduction, but participation of the mPFC has not been.…”

Facilitation of Extinction Learning for Contextual Fear Memory by PEPA: A Potentiator of AMPA Receptors

“…Quantitative PCR analysis of AMPA receptor mRNA expression As mentioned above, PEPA preferentially acts on flop variants and GluR3/4 subunits (Sekiguchi et al, 1997(Sekiguchi et al, , 2002. In contrast, CYZ preferentially acts on flip variants (Partin et al, 1994).…”

“…In the present study, we investigated the effects of 4-[2-(phenylsulfonylamino)ethylthio]-2,6-difluorophenoxyacetamide (PEPA), a flop splice variant and GluR3/4-prefrerring potentiator of AMPA receptors (Sekiguchi et al, 1997(Sekiguchi et al, , 1998, on extinction learning. Potentiators for AMPA receptors are small chemical compounds that enhance AMPA receptor channel activity by modulating receptor kinetics such as desensitization and deactivation [in the case of PEPA (Sekiguchi et al, 2002)].…”