The effects of muscimol and AMN082 injections into the medial prefrontal cortex on the expression and extinction of conditioned fear in mice.

The medial prefrontal cortex (mPFC), in particular its infralimbic part, is a key region in mediating the extinction of conditioned fear. There is some evidence that the metabotropic glutamate receptor 7 (mGluR7) may be involved in the mediation or modulation of extinction. The aim of present study was to assess the potential role of mGluR7 in the mPFC in the extinction of conditioned fear in mice by local injections of AMN082, a positive allosteric modulator of mGluR7. Furthermore, for comparison we injected the GABA-A receptor agonist muscimol, which should lead to a temporary inactivation of mPFC. We found impaired between-session extinction of conditioned fear for the muscimol group as well as a decrease in fear expression. However, local injections of AMN082 into the mPFC had no effects. Overall, the results of the experiment add to a growing body of evidence that mPFC, especially the infralimbic region, is crucial in the extinction of fear memory.