Nicotine self-administration and withdrawal: modulation of anxiety in the social interaction test in rats.
BACKGROUND
Most smokers report smoking has an anxiolytic effect, which may contribute to nicotine dependence.


OBJECTIVE
To examine effects in the social interaction test (SI) of anxiety after 4 weeks' self-administered nicotine (15 infusions of 0.03 mg/kg, totalling 0.45 mg/kg per day), and after 24 and 72 h of withdrawal. The effect of exposure to the operant chamber on withdrawal responses was also examined.


METHODS
Animals were trained to self-administer saline or nicotine and after 4 weeks they were tested in SI after their daily self-administration session. Animals were retested after 24 and 72 h withdrawal, when they were either taken directly from the home cage or were tested 5 min after a 30-min exposure to the operant chamber.


RESULTS
Compared with the saline control group, the animals that had been self-administering nicotine for 4 weeks showed decreased social interaction with no decrease in locomotor activity, indicating a significant anxiogenic effect of the nicotine infusions. There was no change in social interaction after 24 and 72 h withdrawal from chronic nicotine, regardless of whether or not the rats were exposed to the operant chamber just prior to being tested.


CONCLUSIONS
Nicotine self-administration is not maintained because of its anxiolytic effect, but despite, or because of, its anxiogenic effect. There was no evidence of an anxiogenic response after either 24 or 72 h of withdrawal and thus increased anxiety on withdrawal from nicotine does not seem to contribute to nicotine self-administration.
Psychopharmacology Research Unit, Centre for Neuroscience, GKT School of Biomedical Sciences, King's College London, UK.
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Irvine
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Bagnalasta
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Marcon
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Motta
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Tessari
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Chiamulera
D000818:Animals; D001007:Anxiety / Q000139:chemically induced* / Q000523:psychology; D003216:Conditioning, Operant / Q000187:drug effects* / Q000502:physiology; D008297:Male; D009043:Motor Activity / Q000187:drug effects* / Q000502:physiology; D009538:Nicotine / Q000008:administration & dosage / Q000494:pharmacology*; D018722:Nicotinic Agonists / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D012646:Self Administration / Q000523:psychology; D012919:Social Behavior; D013375:Substance Withdrawal Syndrome / Q000523:psychology
D018722:Nicotinic Agonists; D009538:Nicotine