title: Inhibition of alcohol self-administration by positive allosteric modulators of the GABAB receptor in rats: lack of tolerance and potentiation of baclofen.
abstract: BACKGROUND
  Treatment with positive allosteric modulators (PAMs) of the GABAB receptor (GABAB PAMs) inhibits several alcohol-motivated behaviors in rodents, including operant, oral alcohol self-administration.
  
  
  OBJECTIVE
  The present study assessed the effects of (a) repeated administration of the GABAB PAMs, GS39783, and rac-BHFF and (b) a combination of an ineffective dose of either GS39783, or rac-BHFF, and an ineffective dose of the prototypic GABAB receptor agonist, baclofen, on operant, oral alcohol self-administration.
  
  
  METHODS
  Studies were conducted using selectively bred Sardinian alcohol-preferring (sP) rats exposed to a standard procedure of fixed ratio (FR) 4 (FR4) schedule of reinforcement for 15 % (v/v) alcohol.
  
  
  RESULTS
  Repeated treatment with GS39783 (50 mg/kg, i.g.) or rac-BHFF (50 mg/kg, i.g.) produced an initial 40 % reduction in number of lever responses for alcohol and amount of self-administered alcohol that was maintained unaltered throughout the 10-day period of the GS39783 treatment and increased throughout the 5-day period of the rac-BHFF treatment. Combination of per se ineffective doses of GS39783 (5 mg/kg, i.g.), or rac-BHFF (5 mg/kg, i.g.), and baclofen (1 mg/kg, i.p.) reduced, by 35-45 %, both number of lever responses for alcohol and amount of self-administered alcohol.
  
  
  CONCLUSIONS
  GS39783 and rac-BHFF (a) reduced alcohol reinforcing properties when given repeatedly, with no development of tolerance, and (b) potentiated baclofen effect. Both sets of data possess translational interest, as they suggest potential effectiveness of GABAB PAMs under chronic treatment and selective potentiation of baclofen effect.
authors.affiliation: Neuroscience Institute, National Research Council of Italy, Section of Cagliari, S.S. 554, km. 4,500, 09042, Monserrato, CA, Italy.
authors.forename: Paola
authors.initials: P
authors.lastname: Maccioni
authors.forename: Daniela
authors.initials: D
authors.lastname: Vargiolu
authors.forename: Andrew W
authors.initials: AW
authors.lastname: Thomas
authors.forename: Pari
authors.initials: P
authors.lastname: Malherbe
authors.forename: Claudia
authors.initials: C
authors.lastname: Mugnaini
authors.forename: Federico
authors.initials: F
authors.lastname: Corelli
authors.forename: Kimberly A
authors.initials: KA
authors.lastname: Leite-Morris
authors.forename: Gian Luigi
authors.initials: GL
authors.lastname: Gessa
authors.forename: Giancarlo
authors.initials: G
authors.lastname: Colombo
mesh_terms: D000428:Alcohol Drinking / Q000188:drug therapy* / Q000235:genetics / Q000523:psychology; D000494:Allosteric Regulation / Q000187:drug effects / Q000502:physiology; D000818:Animals; D001418:Baclofen / Q000008:administration & dosage*; D001572:Benzofurans / Q000008:administration & dosage; D003517:Cyclopentanes / Q000008:administration & dosage; D004357:Drug Synergism; D004361:Drug Tolerance / Q000502:physiology; D000431:Ethanol / Q000008:administration & dosage* / Q000037:antagonists & inhibitors*; D008297:Male; D011743:Pyrimidines / Q000008:administration & dosage; D051381:Rats; D018080:Receptors, GABA-B / Q000502:physiology*; D012646:Self Administration
chemical_list: C532129:(R,S)-5,7-di-tert-butyl-3-hydroxy-3-trifluoromethyl-3H-benzofuran-2-one; D001572:Benzofurans; D003517:Cyclopentanes; C478058:N,N'-dicyclopentyl-2-methylsulfanyl-5-nitro-pyrimidine-4,6-diamine; D011743:Pyrimidines; D018080:Receptors, GABA-B; D000431:Ethanol; D001418:Baclofen