• Travis E Brown, Melissa R Forquer, Joseph W Harding, John W Wright, and Barbara A Sorg.
• Department of Veterinary and Comparative Anatomy, Physiology and Pharmacology, Washington State University, Pullman, Washington 99164, USA.
• Synapse. 2008 Dec 1; 62 (12): 886-9.

AbstractRecently we have shown that inhibition of matrix metalloproteinase (MMP) activity suppresses the reinstatement of cocaine-primed conditioned place preference (CPP) in rats. Here we explored whether cocaine-primed reinstatement was associated with increased activity of the gelatinases, MMP-2 or MMP-9, in the medial prefrontal cortex (mPFC) or dorsal hippocampus. Male Sprague-Dawley rats underwent training for cocaine-CPP followed by extinction sessions and either saline- or cocaine-priming injections. Cocaine-induced reinstatement produced significant increases in mPFC MMP-9 activity at 1, 3 and 24 hr after injection compared with saline controls. No changes in MMP-9 occurred in the hippocampus or in MMP-2 activity in either brain region. Also, no changes in mPFC MMP-9 activity were observed 1 hr after reinstatement in animals given no extinction sessions but equivalent time off in the home cage. Finally, MMP-3 protein levels were not different in either brain region at any of the three time points assessed. These results suggest that an elevation in MMP-9 activity in the mPFC may contribute to synaptic remodeling important for the reactivation of a cocaine memory, or alternatively, for the modification of a competing extinction memory during reinstatement.(c) 2008 Wiley-Liss, Inc.

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