Vagus Nerve Stimulation Enhances Extinction of Conditioned Fear in Rats and Modulates Arc Protein, CaMKII, and GluN2B-Containing NMDA Receptors in the Basolateral Amygdala

Figure 4

Ifenprodil blocks extinction learning in VNS-extinction and EE rats. (a) Timeline of behavioral protocol. On days 1 and 2 rats were subjected to auditory fear conditioning (AFC) followed by a conditioned fear response test (CFRT) on day 3. On day 4 rats underwent extinction training (EXT) or extended-extinction (EE) training that was immediately followed by an i.p. injection of ifenprodil or vehicle. On day 5 rats underwent a second CFRT (CFRT 2). (b) VNS-extinction and EE rats given a vehicle injection immediately after extinction training show a significant decrease in freezing levels during the second conditioned fear response test (CFRT 2) compared to sham-vehicle rats (). VNS-vehicle rats show significantly lower freezing levels during CFRT 2 compared to VNS-ifenprodil rats ().

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