title: Influence of GABAAR monoliganded states on GABAergic responses.
abstract: To reach the open state, the GABA(A) receptor (GABA(A)R) is assumed to bind two agonist molecules. Although it is currently believed that GABA(A)R could also operate in the monoliganded state, the gating properties of singly bound GABA(A)R are poorly understood and their physiological role is still obscure. In the present study, we characterize for the first time the gating properties of singly bound GABA(A)Rs by using a mutagenesis approach and we propose that monoliganded GABA(A)R contribute in shaping synaptic responses. At saturating GABA concentrations, currents mediated by recombinant GABA(A)Rs with a single functional binding site display slow onset, fast deactivation kinetics, and slow rate of desensitization-resensitization. GABA(A)Rs with two binding sites activated by brief pulses of subsaturating GABA concentrations (in the range of the GABA concentration profile in the synaptic cleft) could also mediate fast deactivating currents, displaying deactivation kinetics similar to those mediated by GABA(A)Rs with a single functional binding site. Model simulations of receptors activated by realistic synaptic GABA waves revealed that a considerable proportion of GABA(A) receptors open in the monoliganded state during synaptic transmission, therefore contributing in shaping IPSCs.
authors.affiliation: Department of Neuroscience and Brain Technologies, The Italian Institute of Technology, Genova, Italy.
authors.forename: Enrica Maria
authors.initials: EM
authors.lastname: Petrini
authors.forename: Thierry
authors.initials: T
authors.lastname: Nieus
authors.forename: Tiziana
authors.initials: T
authors.lastname: Ravasenga
authors.forename: Francesca
authors.initials: F
authors.lastname: Succol
authors.forename: Stefania
authors.initials: S
authors.lastname: Guazzi
authors.forename: Fabio
authors.initials: F
authors.lastname: Benfenati
authors.forename: Andrea
authors.initials: A
authors.lastname: Barberis
mesh_terms: D004594:Electrophysiology; D057809:HEK293 Cells; D006801:Humans; D007150:Immunohistochemistry; D018613:Microscopy, Confocal; D009433:Neural Inhibition / Q000502:physiology*; D010957:Plasmids; D016133:Polymerase Chain Reaction; D011963:Receptors, GABA-A / Q000235:genetics / Q000378:metabolism*; D009435:Synaptic Transmission / Q000502:physiology*; D014162:Transfection / Q000379:methods; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: D011963:Receptors, GABA-A; D005680:gamma-Aminobutyric Acid