Gap junctions synchronize the firing of inhibitory interneurons in guinea pig hippocampus.
The convulsant 4-aminopyridine (4AP) facilitates the synchronous firing of interneurons in the hippocampus, eliciting giant inhibitory postsynaptic potentials (IPSPs) in CA3 pyramidal cells. We used the gap junction blocker carbenoxolone to investigate the role of electrotonic coupling in both the initiation and the maintenance of 4AP-facilitated inhibitory circuit oscillations. Carbenoxolone abolished all synchronized IPSPs in CA3 cells elicited by 4AP in the presence of ionotropic glutamate receptor blockers. Carbenoxolone also blocked the isolated synchronized GABA(B) IPSPs generated in CA3 cells by a subpopulation of interneurons. These data confirm that: (1) the interneurons producing GABA(B) responses in CA3 cells are electrotonically coupled, and (2) gap junctions among interneurons are essential for initiating synchronized interneuron oscillatory firing in 4AP.
Yang
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Department of Physiology and Pharmacology, Box 29, SUNY Downstate Medical Center, 450 Clarkson Avenue, Brooklyn, NY 11203, USA.
Michelson
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HB
D015761:4-Aminopyridine / Q000494:pharmacology; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000494:pharmacology; D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D001640:Bicuculline / Q000031:analogs & derivatives* / Q000494:pharmacology; D002229:Carbenoxolone / Q000494:pharmacology; D003292:Convulsants / Q000494:pharmacology; D005071:Evoked Potentials / Q000187:drug effects / Q000502:physiology*; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D058787:GABA-A Receptor Antagonists; D017629:Gap Junctions / Q000187:drug effects / Q000502:physiology*; D006168:Guinea Pigs; D006624:Hippocampus / Q000187:drug effects / Q000502:physiology*; D007395:Interneurons / Q000187:drug effects / Q000502:physiology*; D010879:Piperazines / Q000494:pharmacology; D017966:Pyramidal Cells / Q000187:drug effects / Q000502:physiology; D018091:Receptors, AMPA / Q000037:antagonists & inhibitors; D018080:Receptors, GABA-B / Q000187:drug effects / Q000502:physiology*; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors; D009435:Synaptic Transmission / Q000187:drug effects
D003292:Convulsants; D018691:Excitatory Amino Acid Antagonists; D058787:GABA-A Receptor Antagonists; D010879:Piperazines; D018091:Receptors, AMPA; D018080:Receptors, GABA-B; D016194:Receptors, N-Methyl-D-Aspartate; C017069:bicuculline methiodide; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; C050592:3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid; D015761:4-Aminopyridine; D002229:Carbenoxolone; D001640:Bicuculline