title: GABAA receptors at hippocampal mossy fibers.
abstract: Presynaptic GABAA receptors modulate synaptic transmission in several areas of the CNS but are not known to have this action in the cerebral cortex. We report that GABAA receptor activation reduces hippocampal mossy fibers excitability but has the opposite effect when intracellular Cl- is experimentally elevated. Synaptically released GABA mimics the effect of exogenous agonists. GABAA receptors modulating axonal excitability are tonically active in the absence of evoked GABA release or exogenous agonist application. Presynaptic action potential-dependent Ca2+ transients in individual mossy fiber varicosities exhibit a biphasic dependence on membrane potential and are altered by GABAA receptors. Antibodies against the alpha2 subunit of GABAA receptors stain mossy fibers. Axonal GABAA receptors thus play a potentially important role in tonic and activity-dependent heterosynaptic modulation of information flow to the hippocampus.
authors.affiliation: Department of Clinical and Experimental Epilepsy, Institute of Neurology, University College London, London, WC1N 3BG, United Kingdom.
authors.forename: Arnaud
authors.initials: A
authors.lastname: Ruiz
authors.forename: Ruth
authors.initials: R
authors.lastname: Fabian-Fine
authors.forename: Ricardo
authors.initials: R
authors.lastname: Scott
authors.forename: Matthew C
authors.initials: MC
authors.lastname: Walker
authors.forename: Dmitri A
authors.initials: DA
authors.lastname: Rusakov
authors.forename: Dimitri M
authors.initials: DM
authors.lastname: Kullmann
mesh_terms: D000818:Animals; D058785:GABA-A Receptor Agonists; D006168:Guinea Pigs; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D019599:Mossy Fibers, Hippocampal / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D051381:Rats; D017207:Rats, Sprague-Dawley; D011963:Receptors, GABA-A / Q000378:metabolism* / Q000648:ultrastructure; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
chemical_list: D058785:GABA-A Receptor Agonists; D011963:Receptors, GABA-A; D005680:gamma-Aminobutyric Acid