Proximally targeted GABAergic synapses and gap junctions synchronize cortical interneurons.
Networks of GABAergic interneurons are implicated in synchronizing cortical activity at gamma frequencies (30-70 Hz). Here we demonstrate that the combined electrical and GABAergic synaptic coupling of basket cells instantaneously entrained gamma-frequency postsynaptic firing in layers 2/3 of rat somatosensory cortex. This entrainment was mediated by rapid curtailment of gap junctional coupling potentials by GABAA receptor-mediated IPSPs. Electron microscopy revealed spatial proximity of gap junctions and GABAergic synapses on somata and dendrites. Electrical coupling alone entrained postsynaptic firing with a phase lag, whereas unitary GABAergic connections were ineffective in gamma-frequency phasing. These observations demonstrate precise spatiotemporal mechanisms underlying action potential timing in oscillating interneuronal networks.
Tamás
G
G
Department of Comparative Physiology, University of Szeged, Középfasor 52, Szeged H-6726, Hungary. gtamas@sol.cc.u-szeged.hu
Buhl
E H
EH
Lörincz
A
A
Somogyi
P
P
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000367:Age Factors; D000818:Animals; D001640:Bicuculline / Q000494:pharmacology; D002450:Cell Communication / Q000502:physiology*; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology; D018756:GABA Antagonists / Q000494:pharmacology; D017629:Gap Junctions / Q000502:physiology* / Q000648:ultrastructure; D007395:Interneurons / Q000166:cytology / Q000502:physiology*; D008854:Microscopy, Electron; D051381:Rats; D017208:Rats, Wistar; D013569:Synapses / Q000502:physiology* / Q000648:ultrastructure; D005680:gamma-Aminobutyric Acid / Q000502:physiology*
D018756:GABA Antagonists; D005680:gamma-Aminobutyric Acid; D001640:Bicuculline