High anxiety is a predisposing endophenotype for loss of control over cocaine, but not heroin, self-administration in rats
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Although high anxiety is commonly associated with drug addiction, its causal role in this disorder is unclear.
In light of strong evidence for dissociable neural mechanisms underlying heroin and cocaine addiction, the present study investigated whether high anxiety predicts the propensity of rats to lose control over intravenous cocaine or heroin self-administration.
Sixty-four rats were assessed for anxiety in the elevated plus-maze, prior to extended access to intravenous cocaine or heroin self-administration.
High-anxious rats, identified in the lower quartile of the population, showed a greater escalation of cocaine, but not heroin, self-administration compared with low-anxious rats selected in the upper quartile of the population. Anxiety scores were also positively correlated with the extent of escalation of cocaine self-administration.
The present data suggest that high anxiety predisposes rats to lose control over cocaine—but not heroin—intake. High anxiety may therefore be a vulnerability trait for the escalation of stimulant but not opiate self-administration.
KeywordsAddiction Anxiety Cocaine Escalation Heroin Self-administration
This work was supported by the United Kingdom Medical Research Council (Grant 9536855 to BJE and Grant G0701500 to JWD) and was conducted within the MRC/Wellcome Trust Behavioural and Clinical Neuroscience Institute. RD was financially supported by a Young Foreign Researcher grant from the University of Poitiers. DB is supported by an INSERM AVENIR grant.
The authors report no competing interests.
DB and BJE were responsible for the study concept. RD, BJE, JWD and DB designed the experiments. RD, YP, ACM and AM performed the experiments. RD and DB performed statistical analyses and designed the figures. RD drafted the manuscript. DB, BJE, JWD and TWR provided critical revision of the manuscript for important intellectual content. All authors critically reviewed content and approved final version for publication.
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