title: Dendritic GABA release depresses excitatory transmission between layer 2/3 pyramidal and bitufted neurons in rat neocortex.
abstract: GABAergic, somatostatin-containing bitufted interneurons in layer 2/3 of rat neocortex are excited via glutamatergic excitatory postsynaptic potentials (EPSPs) by pyramidal neurons located in the same cortical layer. Pair recordings showed that short bursts of backpropagating dendritic action potentials (APs) reduced the amplitude of unitary EPSPs. EPSP depression was dependent on a rise in dendritic [Ca2+]. The effect was blocked by the GABA(B) receptor (GABA(B)-R) antagonist CGP55845A and was mimicked by the GABA(B)-R agonist baclofen. As presynaptic GABA(B)-Rs were activated neither by somatostatin nor by GABA released from axon collaterals of the bitufted cell, we conclude that GABA(B)-Rs were activated by a retrograde messenger, most likely GABA, released from the dendrite. Because synaptic depression was prevented by loading bitufted neurons with GDP-beta-S, it is likely to be caused by exocytotic GABA release from dendrites.
authors.affiliation: Abteilung Zellphysiologie, Max-Plank-Institut für Medizinische Forschung, Heidelberg, Federal Republic of Germany. yuri.zilberter@neuro.ki.se
authors.forename: Y
authors.initials: Y
authors.lastname: Zilberter
authors.forename: K M
authors.initials: KM
authors.lastname: Kaiser
authors.forename: B
authors.initials: B
authors.lastname: Sakmann
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000818:Animals; D002118:Calcium / Q000502:physiology; D002462:Cell Membrane / Q000502:physiology; D003712:Dendrites / Q000378:metabolism / Q000502:physiology*; D004594:Electrophysiology; D018846:Excitatory Amino Acids / Q000502:physiology*; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology; D058786:GABA-B Receptor Agonists; D058788:GABA-B Receptor Antagonists; D066298:In Vitro Techniques; D007395:Interneurons / Q000502:physiology / Q000648:ultrastructure; D019579:Neocortex / Q000166:cytology / Q000502:physiology* / Q000648:ultrastructure; D009474:Neurons / Q000502:physiology* / Q000648:ultrastructure; D018408:Patch-Clamp Techniques; D017729:Presynaptic Terminals / Q000502:physiology; D017966:Pyramidal Cells / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D013569:Synapses / Q000502:physiology; D009435:Synaptic Transmission / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism / Q000502:physiology*
chemical_list: D018846:Excitatory Amino Acids; D058786:GABA-B Receptor Agonists; D058788:GABA-B Receptor Antagonists; D005680:gamma-Aminobutyric Acid; D002118:Calcium