title: Benzodiazepine modulation of homomeric GABAAρ1 receptors: differential effects of diazepam and 4'-chlorodiazepam.
abstract: GABA(A) receptors (GABA(A)Rs) are ligand-gated ion channels that mediate inhibitory neurotransmission in the central nervous system (CNS). They are members of the Cys-loop receptor family and display marked structural and functional heterogeneity. Many GABA(A)Rs receptor subtypes are allosterically modulated by benzodiazepines (BDZs), which are drugs extensively used as anxiolytics, sedative-hypnotics and anticonvulsants. One high-affinity site and at least three additional low-affinity sites for BDZ recognition have been identified in several heteromeric and homomeric variants of the GABA(A)Rs (e.g.: α1β2γ2, α1β2/3, β3, etc.). However, the modulation of homomeric GABA(A)ρRs by BDZs was not previously revealed, and these receptors, for a long a time, were assumed to be fully insensitive to the actions of these drugs. In the present study, human homomeric GABA(A)ρ1 receptors were expressed in Xenopus oocytes and GABA-evoked responses electrophysiologically recorded in the presence or absence of BDZs. GABA(A)ρ1 receptor-mediated responses were modulated by diazepam and 4'-chlorodiazepam in the micromolar range, in a concentration-dependent, voltage-independent and reversible manner. Diazepam produced potentiating effects on GABA-evoked Cl(-) currents and 4'-Cl diazepam induced biphasic effects depending on the GABA concentration, whereas Ro15-4513 and alprazolam were negative modulators. BDZ actions were insensitive to flumazenil. Other BDZs showed negligible activity at equivalent experimental conditions. Our results suggest that GABA(A)ρ1 receptor function can be selectively and differentially modulated by BDZs.
authors.affiliation: Laboratorio de Neurobiología Celular y Molecular, Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres" (INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Vuelta de Obligado 2490, Ciudad Autónoma de Buenos Aires CP 1428, Argentina.
authors.forename: Andrea N
authors.initials: AN
authors.lastname: Beltrán González
authors.affiliation: Laboratorio de Neurobiología Celular y Molecular, Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres" (INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Vuelta de Obligado 2490, Ciudad Autónoma de Buenos Aires CP 1428, Argentina.
authors.forename: Pablo E
authors.initials: PE
authors.lastname: Pomata
authors.affiliation: Laboratorio de Neurobiología Celular y Molecular, Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres" (INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Vuelta de Obligado 2490, Ciudad Autónoma de Buenos Aires CP 1428, Argentina.
authors.forename: Juan D
authors.initials: JD
authors.lastname: Goutman
authors.affiliation: Laboratorio de Neurobiología Celular y Molecular, Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres" (INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Vuelta de Obligado 2490, Ciudad Autónoma de Buenos Aires CP 1428, Argentina.
authors.forename: Javier
authors.initials: J
authors.lastname: Gasulla
authors.affiliation: Laboratorio de Neurobiología Celular y Molecular, Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres" (INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Vuelta de Obligado 2490, Ciudad Autónoma de Buenos Aires CP 1428, Argentina.
authors.forename: Mary
authors.initials: M
authors.lastname: Chebib
authors.affiliation: Laboratorio de Neurobiología Celular y Molecular, Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres" (INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Vuelta de Obligado 2490, Ciudad Autónoma de Buenos Aires CP 1428, Argentina. Electronic address: danieljcalvo@gmail.com.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Calvo
mesh_terms: D000818:Animals; D001569:Benzodiazepines / Q000494:pharmacology*; D001570:Benzodiazepinones / Q000494:pharmacology*; D003975:Diazepam / Q000494:pharmacology*; D055724:Electrophysiological Phenomena / Q000187:drug effects; D018757:GABA Modulators / Q000494:pharmacology*; D006801:Humans; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism; D011963:Receptors, GABA-A / Q000378:metabolism*; D014982:Xenopus laevis / Q000378:metabolism
chemical_list: D001570:Benzodiazepinones; D018757:GABA Modulators; D011963:Receptors, GABA-A; D001569:Benzodiazepines; C028513:4'-chlorodiazepam; D003975:Diazepam
keywords: Benzodiazepines; Bicuculline insensitive GABA receptors; Cys-loop receptors; GABA receptors; GABA(A)ρ receptors