Gap junctions synchronize the firing of inhibitory interneurons in guinea pig hippocampus

• Published in: Brain research 2001-07, Vol.907 (1), p.139-143
• Main Authors: Yang, Qizong, Michelson, Hillary B
• Format: Article
• Language: English
• Subjects: 4-Aminopyridine; 4-Aminopyridine - pharmacology; 6-Cyano-7-nitroquinoxaline-2,3-dione - pharmacology; Action Potentials - drug effects; Animals; Bicuculline - analogs & derivatives; Bicuculline - pharmacology; Biological and medical sciences; carbenoxolone; Carbenoxolone - pharmacology; Central nervous system; Convulsants - pharmacology; Electrophysiology; Electrotonic coupling; Evoked Potentials - drug effects; Evoked Potentials - physiology; Excitatory Amino Acid Antagonists - pharmacology; Fundamental and applied biological sciences. Psychology; GABA-A Receptor Antagonists; Gap junctions; Gap Junctions - drug effects; Gap Junctions - physiology; Guinea Pigs; Hippocampus - drug effects; Hippocampus - physiology; Inhibition; Interneuron; Interneurons - drug effects; Interneurons - physiology; Piperazines - pharmacology; Pyramidal Cells - drug effects; Pyramidal Cells - physiology; Receptors, AMPA - antagonists & inhibitors; Receptors, GABA-B - drug effects; Receptors, GABA-B - physiology; Receptors, N-Methyl-D-Aspartate - antagonists & inhibitors; Synaptic Transmission - drug effects; Vertebrates: nervous system and sense organs
• ISSN: 0006-8993; 1872-6240
• DOI: 10.1016/S0006-8993(01)02582-3

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.