title: Use-dependent AMPA receptor block reveals segregation of spontaneous and evoked glutamatergic neurotransmission.
abstract: Earlier findings had suggested that spontaneous and evoked glutamate release activates non-overlapping populations of NMDA receptors. Here, we evaluated whether AMPA receptor populations activated by spontaneous and evoked release show a similar segregation. To track the receptors involved in spontaneous or evoked neurotransmission, we used a polyamine agent, philanthotoxin, that selectively blocks AMPA receptors lacking GluR2 subunits in a use-dependent manner. In hippocampal neurons obtained from GluR2-deficient mice, philanthotoxin application decreased AMPA-receptor-mediated spontaneous miniature EPSCs (AMPA-mEPSCs) down to 20% of their initial level within 5 min. In contrast, the same philanthotoxin application at rest decreased the subsequent AMPA-receptor-mediated evoked EPSCs (eEPSCs) only down to 80% of their initial value. A 10-min-long perfusion of philanthotoxin further decreased AMPA-eEPSC amplitudes to 60% of their initial magnitude, which remained substantially higher than the level of AMPA-mEPSC block achieved within 5 min. Finally, stimulation after removal of philanthotoxin resulted in reversal of AMPA-eEPSC block, verifying strict use dependence of philanthotoxin. These results support the notion that spontaneous and evoked neurotransmission activate distinct sets of AMPA receptors and bolster the hypothesis that synapses harbor separate microdomains of evoked and spontaneous signaling.
authors.affiliation: Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9111, USA.
authors.forename: Yildirim
authors.initials: Y
authors.lastname: Sara
authors.forename: Manjot
authors.initials: M
authors.lastname: Bal
authors.forename: Megumi
authors.initials: M
authors.lastname: Adachi
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Monteggia
authors.forename: Ege T
authors.initials: ET
authors.lastname: Kavalali
mesh_terms: D000779:Anesthetics, Local / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D002478:Cells, Cultured; D016291:Dizocilpine Maleate / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology*; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects* / Q000235:genetics; D005260:Female; D018698:Glutamic Acid / Q000378:metabolism* / Q000494:pharmacology; D006624:Hippocampus / Q000166:cytology; D008012:Lidocaine / Q000031:analogs & derivatives / Q000494:pharmacology; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D018408:Patch-Clamp Techniques; D011073:Polyamines / Q000494:pharmacology*; D018091:Receptors, AMPA / Q000037:antagonists & inhibitors* / Q000172:deficiency / Q000502:physiology; D013779:Tetrodotoxin / Q000494:pharmacology; D014633:Valine / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: D000779:Anesthetics, Local; D018691:Excitatory Amino Acid Antagonists; D011073:Polyamines; D018091:Receptors, AMPA; C012647:QX-314; D018698:Glutamic Acid; D013779:Tetrodotoxin; D016291:Dizocilpine Maleate; C056639:2-amino-5-phosphopentanoic acid; C034092:delta-philanthotoxin; D008012:Lidocaine; D014633:Valine; C104722:glutamate receptor ionotropic, AMPA 2