Limits...
Cues paired with either rapid or slower self-administered cocaine injections acquire similar conditioned rewarding properties.

Samaha AN, Minogianis EA, Nachar W - PLoS ONE (2011)

Bottom Line: Rats in both the 5- and 90-second groups pressed more on the active versus inactive lever following extensive (24 sessions) but not following limited (3 sessions) self-administration training.There were no group differences in this behaviour.However, the rewarding properties of the cues were not "forgotten" because on withdrawal days 32-33, amphetamine selectively enhanced active-lever pressing, and did so to a similar extent in both groups.

View Article: PubMed Central - PubMed

Affiliation: Department of Pharmacology, Faculty of Medicine, Université de Montréal, Montréal, Québec, Canada. Anna.samaha@umontreal.ca

ABSTRACT
The faster drugs of abuse reach the brain, the more addictive they can be. It is not known why this is. Environmental stimuli associated with drugs can promote the development and persistence of addiction by invigorating and precipitating drug-seeking behaviour. We determined, therefore, whether cues associated with the self-administration of rapidly delivered cocaine (injected intravenously over 5 versus 90 seconds) would acquire greater conditioned rewarding properties, as assessed by the performance of an operant response reinforced solely by the cues. Rats nose-poked for intravenous cocaine infusions delivered either over 5 or 90 seconds. Discrete visual cues accompanied each infusion. The rats could then press a lever to obtain the cues--now a conditioned reward--or an inactive lever. Rats in both the 5- and 90-second groups pressed more on the active versus inactive lever following extensive (24 sessions) but not following limited (3 sessions) self-administration training. There were no group differences in this behaviour. Following withdrawal from cocaine self-administration, lever discrimination progressively abated in both groups and was lost by withdrawal day 30. However, the rewarding properties of the cues were not "forgotten" because on withdrawal days 32-33, amphetamine selectively enhanced active-lever pressing, and did so to a similar extent in both groups. Thus, cues paired with rapid or slower cocaine delivery acquire similar conditioned rewarding properties. We conclude, therefore, that the rapid delivery of cocaine to the brain promotes addiction by mechanisms that might not involve a greater ability of drug cues to control behaviour.

Show MeSH

Related in: MedlinePlus

In both the 5- and 90-s groups, discrimination between the CR and NCR levers is observed following extensive (panel B) but not limited (panel A) cocaine self-administration experience.Limited self-administration experience consisted of 3 self-administration sessions. Extensive self-administration experience consisted of 24 self-administration sessions. Values are mean ± SEM. n's = 6–7/group. s, seconds; CR, conditioned reward lever; NCR, non-conditioned reward lever; SA, cocaine self-administration. *p<0.05 compared with NCR within the same group.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3198427&req=5

pone-0026481-g006: In both the 5- and 90-s groups, discrimination between the CR and NCR levers is observed following extensive (panel B) but not limited (panel A) cocaine self-administration experience.Limited self-administration experience consisted of 3 self-administration sessions. Extensive self-administration experience consisted of 24 self-administration sessions. Values are mean ± SEM. n's = 6–7/group. s, seconds; CR, conditioned reward lever; NCR, non-conditioned reward lever; SA, cocaine self-administration. *p<0.05 compared with NCR within the same group.

Mentions: Figure 6 shows CR versus NCR lever presses as a function of group, following three (A) or twenty-four (B) cocaine self-administration sessions. There was no main effect of group (F(1, 11) = 0.28, p = 0.61). There was an overall main effect of lever (F(1, 11) = 27.8, p = 0.000) and a significant lever x self-administration experience interaction (F(1, 11) = 8.202, p = 0.015), indicating that lever discrimination differed as a function of self-administration experience. Further investigation of this interaction effect revealed that in both the 5- and 90-s groups, there was no difference in CR vs. NCR lever pressing following limited cocaine self-administration experience [i.e., 3 self-administration sessions; (A), 5-s group, t(6) = 0.18, p = 0.87; 90-s group, t(5) = 1.58, p = 0.18 ], but that CR lever presses were greater than NCR lever presses following extensive cocaine self-administration experience [i.e., 24 self-administration sessions; (B), 5-s group, t(6) = 4.168, p = 0.006; 90-s group, t(5) = 4.437, p = 0.007]. Thus, following extensive, but not limited self-administration experience, both groups discriminated between the two levers and spontaneously acquired a new operant response, reinforced solely by the conditioned reward.


Cues paired with either rapid or slower self-administered cocaine injections acquire similar conditioned rewarding properties.

Samaha AN, Minogianis EA, Nachar W - PLoS ONE (2011)

In both the 5- and 90-s groups, discrimination between the CR and NCR levers is observed following extensive (panel B) but not limited (panel A) cocaine self-administration experience.Limited self-administration experience consisted of 3 self-administration sessions. Extensive self-administration experience consisted of 24 self-administration sessions. Values are mean ± SEM. n's = 6–7/group. s, seconds; CR, conditioned reward lever; NCR, non-conditioned reward lever; SA, cocaine self-administration. *p<0.05 compared with NCR within the same group.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3198427&req=5

pone-0026481-g006: In both the 5- and 90-s groups, discrimination between the CR and NCR levers is observed following extensive (panel B) but not limited (panel A) cocaine self-administration experience.Limited self-administration experience consisted of 3 self-administration sessions. Extensive self-administration experience consisted of 24 self-administration sessions. Values are mean ± SEM. n's = 6–7/group. s, seconds; CR, conditioned reward lever; NCR, non-conditioned reward lever; SA, cocaine self-administration. *p<0.05 compared with NCR within the same group.
Mentions: Figure 6 shows CR versus NCR lever presses as a function of group, following three (A) or twenty-four (B) cocaine self-administration sessions. There was no main effect of group (F(1, 11) = 0.28, p = 0.61). There was an overall main effect of lever (F(1, 11) = 27.8, p = 0.000) and a significant lever x self-administration experience interaction (F(1, 11) = 8.202, p = 0.015), indicating that lever discrimination differed as a function of self-administration experience. Further investigation of this interaction effect revealed that in both the 5- and 90-s groups, there was no difference in CR vs. NCR lever pressing following limited cocaine self-administration experience [i.e., 3 self-administration sessions; (A), 5-s group, t(6) = 0.18, p = 0.87; 90-s group, t(5) = 1.58, p = 0.18 ], but that CR lever presses were greater than NCR lever presses following extensive cocaine self-administration experience [i.e., 24 self-administration sessions; (B), 5-s group, t(6) = 4.168, p = 0.006; 90-s group, t(5) = 4.437, p = 0.007]. Thus, following extensive, but not limited self-administration experience, both groups discriminated between the two levers and spontaneously acquired a new operant response, reinforced solely by the conditioned reward.

Bottom Line: Rats in both the 5- and 90-second groups pressed more on the active versus inactive lever following extensive (24 sessions) but not following limited (3 sessions) self-administration training.There were no group differences in this behaviour.However, the rewarding properties of the cues were not "forgotten" because on withdrawal days 32-33, amphetamine selectively enhanced active-lever pressing, and did so to a similar extent in both groups.

View Article: PubMed Central - PubMed

Affiliation: Department of Pharmacology, Faculty of Medicine, Université de Montréal, Montréal, Québec, Canada. Anna.samaha@umontreal.ca

ABSTRACT
The faster drugs of abuse reach the brain, the more addictive they can be. It is not known why this is. Environmental stimuli associated with drugs can promote the development and persistence of addiction by invigorating and precipitating drug-seeking behaviour. We determined, therefore, whether cues associated with the self-administration of rapidly delivered cocaine (injected intravenously over 5 versus 90 seconds) would acquire greater conditioned rewarding properties, as assessed by the performance of an operant response reinforced solely by the cues. Rats nose-poked for intravenous cocaine infusions delivered either over 5 or 90 seconds. Discrete visual cues accompanied each infusion. The rats could then press a lever to obtain the cues--now a conditioned reward--or an inactive lever. Rats in both the 5- and 90-second groups pressed more on the active versus inactive lever following extensive (24 sessions) but not following limited (3 sessions) self-administration training. There were no group differences in this behaviour. Following withdrawal from cocaine self-administration, lever discrimination progressively abated in both groups and was lost by withdrawal day 30. However, the rewarding properties of the cues were not "forgotten" because on withdrawal days 32-33, amphetamine selectively enhanced active-lever pressing, and did so to a similar extent in both groups. Thus, cues paired with rapid or slower cocaine delivery acquire similar conditioned rewarding properties. We conclude, therefore, that the rapid delivery of cocaine to the brain promotes addiction by mechanisms that might not involve a greater ability of drug cues to control behaviour.

Show MeSH
Related in: MedlinePlus