Preexposure during or following adolescence differently affects nicotine-rewarding properties in adult rats.
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.
Adriani
Walter
W
INSERM U. 588, Institut François Magendie, Domaine de Carreire, Rue C. Saint-Saëns, Bordeaux Cedex, 33077, France. adriani@iss.it
Deroche-Gamonet
Véronique
V
Le Moal
Michel
M
Laviola
Giovanni
G
Piazza
Pier Vincenzo
PV
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*
D009538:Nicotine