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Am J Transl Res 2012;4(4):422-431
Original Article
Extinction bursts in rats trained to self-administer nicotine or food in
1-h daily sessions
Abhiram Pushparaj, Yaroslaw Pryslawsky, Benoit Forget, Yijin Yan, Bernard Le Foll
Translational Addiction Research Laboratory, Campbell Family Mental Health Research Institute, Centre for
Addiction and Mental Health, Toronto, Canada; Departments of Family and Community Medicine, Pharmacology,
Psychiatry, Institute of Medical Sciences, University of Toronto, Toronto, Canada; Addictions Program, Centre for
Addiction and Mental Health, Toronto, Canada
Received August 6, 2012; accepted September 11, 2012; Epub October 10, 2012; Published October 30, 2012
Abstract: Extinction bursts are characterized by a temporary increase in responding when drug access is
withheld from rats trained to self-administer drugs of abuse. Thus far, one study has examined extinction bursts
for nicotine self-administration using a 23-h access paradigm [1]. Here we examined extinction bursts using
previously published and unpublished data in which rats were trained to self-administer nicotine
(0.03mg/kg/infusion) or food pellets (as a comparator) in 1-h sessions under an FR5 schedule of reinforcement
followed by 1-h extinction sessions. Analysis of response rates during nicotine self-administration (NSA) was
indicative of a loading phase, as response rates were significantly higher at the beginning of the session, which
was not observed for food self-administration. At the start of extinction for both food and nicotine, although
sessional response rates did not increase, there was an increase in response rate during the first 5-min of the
first extinction session relative to self-administration. This transient extinction burst following nicotine was
observed in a minority of subjects and correlated with the number of nicotine infusions obtained during
self-administration. This transient extinction burst following food was observed in all subjects. Nicotine and food
produce more transient extinction bursts compared to other drugs of abuse and only for a minority of animals in
the case of nicotine. This study supports the presence of a loading phase in rats trained to self-administer
nicotine in 1-r daily sessions and the presence of a transient extinction burst. (AJTR1208003).
Keywords: Nicotine, self-administration, extinction, extinction burst, drug seeking, rats
Address all correspondence to:
Dr. Bernard Le Foll, Translational Addiction Research Laboratory, Centre for Addiction and Mental Health (CAMH),
33 Russell Street, Toronto, Ontario, Canada. M5S 2S1. Tel: 416.535.8501, ext. 4772; Fax: 416.595.6922; E-mail:
bernard_lefoll@camh.net
Original Article
Extinction bursts in rats trained to self-administer nicotine or food in
1-h daily sessions
Abhiram Pushparaj, Yaroslaw Pryslawsky, Benoit Forget, Yijin Yan, Bernard Le Foll
Translational Addiction Research Laboratory, Campbell Family Mental Health Research Institute, Centre for
Addiction and Mental Health, Toronto, Canada; Departments of Family and Community Medicine, Pharmacology,
Psychiatry, Institute of Medical Sciences, University of Toronto, Toronto, Canada; Addictions Program, Centre for
Addiction and Mental Health, Toronto, Canada
Received August 6, 2012; accepted September 11, 2012; Epub October 10, 2012; Published October 30, 2012
Abstract: Extinction bursts are characterized by a temporary increase in responding when drug access is
withheld from rats trained to self-administer drugs of abuse. Thus far, one study has examined extinction bursts
for nicotine self-administration using a 23-h access paradigm [1]. Here we examined extinction bursts using
previously published and unpublished data in which rats were trained to self-administer nicotine
(0.03mg/kg/infusion) or food pellets (as a comparator) in 1-h sessions under an FR5 schedule of reinforcement
followed by 1-h extinction sessions. Analysis of response rates during nicotine self-administration (NSA) was
indicative of a loading phase, as response rates were significantly higher at the beginning of the session, which
was not observed for food self-administration. At the start of extinction for both food and nicotine, although
sessional response rates did not increase, there was an increase in response rate during the first 5-min of the
first extinction session relative to self-administration. This transient extinction burst following nicotine was
observed in a minority of subjects and correlated with the number of nicotine infusions obtained during
self-administration. This transient extinction burst following food was observed in all subjects. Nicotine and food
produce more transient extinction bursts compared to other drugs of abuse and only for a minority of animals in
the case of nicotine. This study supports the presence of a loading phase in rats trained to self-administer
nicotine in 1-r daily sessions and the presence of a transient extinction burst. (AJTR1208003).
Keywords: Nicotine, self-administration, extinction, extinction burst, drug seeking, rats
Address all correspondence to:
Dr. Bernard Le Foll, Translational Addiction Research Laboratory, Centre for Addiction and Mental Health (CAMH),
33 Russell Street, Toronto, Ontario, Canada. M5S 2S1. Tel: 416.535.8501, ext. 4772; Fax: 416.595.6922; E-mail:
bernard_lefoll@camh.net
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