title: Alpha1- and alpha2-containing GABAA receptor modulation is not necessary for benzodiazepine-induced hyperphagia.
abstract: Benzodiazepines increase food intake, an effect attributed to their ability to enhance palatability. We investigated which GABA(A) receptor subtypes may be involved in mediating benzodiazepine-induced hyperphagia. The role of the alpha2 subtype was investigated by observing the effects of midazolam, on the behavioural satiety sequence in mice with targeted deletion of the alpha2 gene (alpha2 knockout). Midazolam (0.125, 0.25 and 0.5mg/kg) increased food intake and the amount of time spent feeding in alpha2 knockout mice, suggesting that BZ-induced hyperphagia does not involve alpha2-containing GABA(A) receptors. We further investigated the roles of alpha1- and alpha3-containing GABA(A) receptors in mediating BZ-induced hyperphagia. We treated alpha2(H101R) mice, in which alpha2-containing receptors are rendered benzodiazepine insensitive, with L-838417, a compound which acts as a partial agonist at alpha2-, alpha3- and alpha5-receptors but is inactive at alpha1-containing receptors. L-838417 (10 and 30 mg/kg) increased food intake and the time spent feeding in both wildtype and alpha2(H101R) mice, demonstrating that benzodiazepine-induced hyperphagia does not require alpha1- and alpha2-containing GABA(A) receptors. These observations, together with evidence against the involvement of alpha5-containing GABA(A) receptors, suggest that alpha3-containing receptors mediate BZ-induced hyperphagia in the mouse.
authors.affiliation: Department of Psychology, University of Sussex, Falmer, Brighton, BN1 9QG, UK.
authors.forename: H V
authors.initials: HV
authors.lastname: Morris
authors.affiliation: Department of Psychology, University of Sussex, Falmer, Brighton, BN1 9QG, UK.
authors.forename: S
authors.initials: S
authors.lastname: Nilsson
authors.affiliation: Department of Psychology, University of Sussex, Falmer, Brighton, BN1 9QG, UK.
authors.forename: C I
authors.initials: CI
authors.lastname: Dixon
authors.affiliation: Department of Psychology, University of Sussex, Falmer, Brighton, BN1 9QG, UK.
authors.forename: D N
authors.initials: DN
authors.lastname: Stephens
authors.affiliation: Department of Psychology, University of Sussex, Falmer, Brighton, BN1 9QG, UK. Electronic address: pete@sussex.ac.uk.
authors.forename: P G
authors.initials: PG
authors.lastname: Clifton
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001569:Benzodiazepines; D003975:Diazepam; D004305:Dose-Response Relationship, Drug; D002149:Energy Intake / Q000187:drug effects* / Q000502:physiology; D005260:Female; D005464:Fluorobenzenes; D018757:GABA Modulators / Q000494:pharmacology*; D058785:GABA-A Receptor Agonists; D006963:Hyperphagia / Q000139:chemically induced / Q000517:prevention & control*; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008874:Midazolam / Q000494:pharmacology*; D011897:Random Allocation; D011963:Receptors, GABA-A / Q000187:drug effects* / Q000502:physiology; D014230:Triazoles
chemical_list: D005464:Fluorobenzenes; D018757:GABA Modulators; D058785:GABA-A Receptor Agonists; D011963:Receptors, GABA-A; D014230:Triazoles; D001569:Benzodiazepines; C409903:L 838,417; D003975:Diazepam; D008874:Midazolam