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. Author manuscript; available in PMC: 2013 Jul 24.
Published in final edited form as: Nat Rev Neurosci. 2011 Oct 5;12(11):685–700. doi: 10.1038/nrn3104

Figure 2. Morphine and cocaine have opposite effects on structural neuroplasticity in the NAc and mPFC.

Figure 2

a | Groups of rats were trained to self-administer morphine or cocaine intravenously for several weeks. The control groups were given daily intravenous infusions of vehicle for the same period of time. After 1 month of withdrawal from the drugs, the rats’ brains were processed using the Golgi staining procedure. Rats that were exposed to cocaine showed increased dendritic branching and increased spine density in both nucleus accumbens (NAc) medium spiny neurons and medial prefrontal cortex (mPFC) pyramidal neurons. By contrast, rats that were exposed to morphine had both reduced dendritic branching and reduced spine density in these brain regions. b | A summary of changes in spine density and dendritic branching that occur after exposure to cocaine or morphine relative to controls. A dissociation between the effects of cocaine and morphine was also observed in the orbital prefrontal cortex (oPFC) and in the primary somatosensory cortex (S1). Data from REF. 71.