As in their previous studies, the researchers found that amphetamine increased dendritic branching and spine density in the nucleus accumbens, and decreased spine density in the parietal cortex. Exposure to the complex environment also increased the dendritic branching and spine density in the nucleus accumbens, and, in contrast to amphetamine, increased dendritic branching and spine density in the parietal cortex as well. Remarkably, animals that had been given amphetamine and then placed in the complex environment did not show the same environmental-induced structural changes in the nucleus acccumbens and parietal cortex as did saline-treated animals in the complex environment.
The results for those animals treated with cocaine were similar, in that prior treatment with cocaine blocked the environment-induced changes in the medium spiny neurons of the nucleus accumbens (the only region examined).
Previous research has shown that cellular and molecular mechanisms responsible for changes in brain structure that occur with experience bear many similarities to those that occur with exposure to drugs of abuse. Certain cell types in some areas of the brain, e.g., the nucleus accumbens and the parietal cortex, have been shown in rats and monkeys to be particularly sensitive to either psychostimulant drugs or to life experiences such as housing conditions.
"The findings from this study indicate that at least some of the cognitiv
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Contact: Michelle Person
mperson@mail.nih.gov
301-443-6245
NIH/National Institute on Drug Abuse
25-Aug-2003