Synapse
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Comparative Study
Increase in matrix metalloproteinase-9 levels in the rat medial prefrontal cortex after cocaine reinstatement of conditioned place preference.
Recently 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. ⋯ 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.