High-frequency stimulation of the infralimbic cortex, following behavioral suppression of PTSD-like symptoms, prevents symptom relapse in mice

Background: We have previously demonstrated, in mice, that antidepressant treatment can prevent relapse of PTSD-like behaviors (avoidance, hyperarousal, and anxiety) through increased activation in the infralimbic cortex (IL) of the medial prefrontal cortex. Objective: Here, we examined whether direct high-frequency stimulation (HFS) of the IL, provoking its heightened activation (i.e., long-term potentiation, LTP), would also prevent the return of PTSD-like symptoms. Methods: A 1.5-mA foot-shock was used to generate PTSD-like symptoms in Swiss mice. In Experiment 1, local field potentials were recorded in the IL to test whether normal IL LTP can be induced after the suppression of PTSD-like symptoms. In Experiment 2, IL HFS was applied after symptom suppression, but prior to the provocation of relapse, to test HFS effect on symptom return. Results: We observed that PTSD-like state was associated with impairment in IL HFS-induced IL LTP. However, IL LTP induction was near normal when PTSD-like symptoms were suppressed. We then found that IL HFS, applied after symptom suppression, prevented symptom return. Conclusions: Increased activation of the IL may be a key mechanism preventing PTSD relapse. Prefrontal cortex deep brain stimulation may, therefore, be relevant for preventing PTSD symptom return in remitted high-risk patients. (C) 2018 Elsevier Inc. All rights reserved.