title: Differential roles of GABA(A) receptor subtypes in benzodiazepine-induced enhancement of brain-stimulation reward.
abstract: Benzodiazepines such as diazepam are widely prescribed as anxiolytics and sleep aids. Continued use of benzodiazepines, however, can lead to addiction in vulnerable individuals. Here, we investigate the neural mechanisms of the behavioral effects of benzodiazepines using the intracranial self-stimulation (ICSS) test, a procedure with which the reward-enhancing effects of these drugs can be measured. Benzodiazepines bind nonselectively to several different GABA(A) receptor subtypes. To elucidate the α subunit(s) responsible for the reward-enhancing effects of benzodiazepines, we examined mice carrying a histidine-to-arginine point mutation in the α1, α2, or α3 subunit, which renders the targeted subunit nonresponsive to diazepam, other benzodiazepines and zolpidem. In wild-type and α1-point-mutated mice, diazepam caused a dose-dependent reduction in ICSS thresholds (reflecting a reward-enhancing effect) that is comparable to the reduction observed following cocaine administration. This effect was abolished in α2- and α3-point-mutant mice, suggesting that these subunits are necessary for the reward-enhancing action of diazepam. α2 Subunits appear to be particularly important, since diazepam increased ICSS thresholds (reflecting an aversive-like effect) in α2-point-mutant animals. Zolpidem, an α1-preferring benzodiazepine-site agonist, had no reward-enhancing effects in any genotype. Our findings implicate α2 and α3 subunit containing GABA(A) receptors as key mediators of the reward-related effects of benzodiazepines. This finding has important implications for the development of new medications that retain the therapeutic effects of benzodiazepines but lack abuse liability.
authors: Laboratory of Genetic Neuropharmacology, McLean Hospital, Belmont, MA, USA.
authors: Lauren M
authors: LM
authors: Reynolds
authors: Elif
authors: E
authors: Engin
authors: Gabriella
authors: G
authors: Tantillo
authors: Hew Mun
authors: HM
authors: Lau
authors: John W
authors: JW
authors: Muschamp
authors: William A
authors: WA
authors: Carlezon
authors: Uwe
authors: U
authors: Rudolph
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects* / Q000502:physiology; D001569:Benzodiazepines / Q000494:pharmacology*; D001921:Brain / Q000187:drug effects* / Q000502:physiology; D003042:Cocaine / Q000008:administration & dosage; D018765:Dopamine Uptake Inhibitors / Q000008:administration & dosage; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D018682:GABA Agents / Q000494:pharmacology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D017354:Point Mutation / Q000235:genetics*; D021122:Protein Subunits / Q000235:genetics; D011963:Receptors, GABA-A / Q000235:genetics / Q000502:physiology*; D012055:Reinforcement Schedule; D012201:Reward; D012653:Self Stimulation / Q000187:drug effects
chemical_list: D018765:Dopamine Uptake Inhibitors; D018682:GABA Agents; D021122:Protein Subunits; D011963:Receptors, GABA-A; D001569:Benzodiazepines; D003042:Cocaine