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Biol Psychiatry. 2005 Nov 1;58(9):751-9. Epub 2005 Aug 11.

Neural and behavioral plasticity associated with the transition from controlled to escalated cocaine use.

Author information

  • 1Department of Psychology (Biopsychology) and Neuroscience Program, University of Michigan, Ann Arbor, MIichigan 48109-1109, USA.

Abstract

BACKGROUND:

Rats given extended access to cocaine develop several symptoms of addiction, including a gradual escalation of drug intake, whereas rats given limited access do not. We asked here whether extended access to cocaine also produces drug-induced sensitization, a form of neurobehavioral plasticity implicated in addiction.

METHODS:

Rats were given limited (1 hour/session) or extended access (6 hours/session) to self-administered cocaine. Following a period of abstinence, rats were selected at random for assessment of their psychomotor response to cocaine or drug-seeking during extinction or for anatomic studies.

RESULTS:

When re-exposed to cocaine, rats allowed extended drug access showed greater drug-seeking behavior and were hypersensitive (sensitized) to the psychomotor activating effects of cocaine compared with rats given limited access. Extended access to cocaine was also associated with a greater increase in the density of dendritic spines on neurons specifically in the core of the nucleus accumbens (and not in the shell or medial or orbital frontal cortex).

CONCLUSIONS:

The transition from stable to escalated cocaine use, a hallmark of addiction, is associated with especially robust behavioral sensitization and synaptic reorganization in the core of the nucleus accumbens.

PMID:
16098484
[PubMed - indexed for MEDLINE]
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