PTSD is a debilitating and costly condition and currently available treatment options have risks and limitations that necessitate development of novel interventions. Collectively, the functional brain imaging reports suggest that patients with PTSD, especially those with the re-experiencing and hypervigilence phenotype, show ventromedial PFC hypoactivation and amygdala hyperactivation in response to symptom provocation, and that treatment, when successful is associated with reduced amygdala and increased ventromedial PFC activation. This project is guided by a neurocircuit model of PTSD dysfunction in which abnormalities in fronto-limbic imbalance, which diminishes capacity for fear extinction learning, and produces PTSD symptoms of re-experiencing and hyperarousal. Thus, our studies aim to bridge the translational gap between theoretical and neurobiological models of PTSD to implementation of clinical practice. The Target Engagement and Dosing Phase of this project, which is a pilot study, will demonstrate target engagement and its association with laboratory measures of PTSD-relevant neural processes.