title: Preexposure during or following adolescence differently affects nicotine-rewarding properties in adult rats.
abstract: BACKGROUND
  Many people come in contact with psychoactive drugs, yet not all of them become addicts. Epidemiology shows that a late approach with cigarette smoking is associated with a lower probability to develop nicotine dependence. Exposure to nicotine during periadolescence, but not similar exposure in the postadolescent period, increases nicotine self-administration in rats, but underlying mechanisms remain poorly understood.
  
  
  OBJECTIVE
  We investigated whether exposure to nicotine during or after adolescence would alter rewarding properties of the same drug at adulthood, as assessed by place conditioning.
  
  
  METHODS
  Periadolescent (PND 34-43) or postadolescent (PND 60-69) rats were injected with saline or nicotine (0.4 mg kg(-1)) for 10 days. The rats received three pairings with saline and three pairings with nicotine (0, 0.3, or 0.6 mg kg(-1)) 5 weeks after pretreatment. The rats were then tested for place conditioning in a drug-free state.
  
  
  RESULTS
  Upon first exposure to the apparatus, animals pretreated with nicotine during adolescence showed elevated novelty-induced activation. The 0.3 (but not the 0.6) mg kg(-1) dose failed to produce both ongoing locomotor sensitization and place conditioning in animals pretreated with nicotine following adolescence. This suggests a rightward shift in the dose-response curve, namely, a reduced efficacy of nicotine. Conversely, the same dose was effective in saline-pretreated controls and noteworthy in rats pretreated during adolescence.
  
  
  CONCLUSIONS
  Exposure following the adolescent period might diminish the risk to develop nicotine dependence. As for human implications, findings are consistent with a reduced vulnerability to nicotine addiction in people who start smoking late in their life.
authors.affiliation: INSERM U. 588, Institut François Magendie, Domaine de Carreire, Rue C. Saint-Saëns, Bordeaux Cedex, 33077, France. adriani@iss.it
authors.forename: Walter
authors.initials: W
authors.lastname: Adriani
authors.forename: Véronique
authors.initials: V
authors.lastname: Deroche-Gamonet
authors.forename: Michel
authors.initials: M
authors.lastname: Le Moal
authors.forename: Giovanni
authors.initials: G
authors.lastname: Laviola
authors.forename: Pier Vincenzo
authors.initials: PV
authors.lastname: Piazza
mesh_terms: D000367:Age Factors; D000818:Animals; D001143:Arousal / Q000187:drug effects; D001245:Association Learning / Q000187:drug effects; D002755:Choice Behavior / Q000187:drug effects; D003214:Conditioning, Classical; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D005106:Exploratory Behavior / Q000187:drug effects; D005260:Female; D007274:Injections, Intraperitoneal; D008297:Male; D009043:Motor Activity / Q000187:drug effects; D009538:Nicotine / Q000008:administration & dosage*; D011292:Premedication; D051381:Rats; D017207:Rats, Sprague-Dawley; D012201:Reward; D012646:Self Administration; D012931:Social Environment; D014029:Tobacco Use Disorder / Q000523:psychology*
chemical_list: D009538:Nicotine