Lidocaine injections targeting IL but not the PL area of prefrontal cortex impairs extinction of auditory fear conditioning in rat

Introduction: Fear has a central role in organizing of defensive behaviors to threat and fear memory is essential to the organism’s survival. Fear learning studies in conscious animals have shown dissociable roles for mPFC and its subregions, PL and IL in mediating different memory processes. While PL is involved in the retrieval or expression of conditioned responses, the suppression and extinction of conditioned responding involve IL. Memory extinction is a new learning and consists of the learned inhibition of retrieval of previously acquired memories. Previous study indicated that many regions of brain especially infralimbic of prefrontal cortex play an essential role in the extinction of fear-based memory. Therefore, the aim of the present study is to examine the role of IL and PL areas in the extinction of auditory fear memory (AFM) by reversible inactivation with lidocaine in rats. Materials and methods: Rats with surgically implanted bilaterally cannula aimed at the IL and PL were trained and tested in an auditory fear condition task. After conditioning rats divided in 4 groups (N=10) were injected with either saline or lidocaine (40ng /0.5μl/side) in IL and PL areas 10 min before extinction training. Conditioned fear was assessed by measuring the percentage of freezing during 3 days, in 24 intervals. Results: Results indicated that inactivation of these areas with lidocaine increased or decreased freezing respectively. In other word IL inactivation impaired acquisition of extinction and extinction memory (P<0.0001). Conclusion: Our data suggest that IL but not the PL plays an important role in fear memory extinction

کلیدواژه ها:

Extinction ، Fear memory ، mPFC ، Lidocaine ، Rat