Imaging the Neuroimmune System in PTSD

In this study, individuals with and without post-traumatic stress disorder (PTSD) will undergo one positron emission tomography (PET) scan using the radiotracer \[11C\]PBR28, which binds to the 18kDa translocator protein (TSPO). A subset of individuals who complete the first PET \[11C\]PBR28 scan will be invited to complete an inflammatory challenge and second PET \[11C\]PBR28 scan. Approximately 3 hours prior to the second \[11C\]PBR28 PET scan, lipopolysaccharide (LPS; endotoxin) will be administered to evoke a robust neuroimmune response. Subjects will also undergo behavioral and cognitive testing. Vital signs, subjective response, and peripheral biomarker levels will be assayed periodically throughout the experimental session. Specific aims: 1) Determine if individuals with PTSD exhibit neuroimmune system disruption relative to well-matched comparators at baseline. 2) Determine if individuals with PTSD exhibit a disrupted neuroimmune response after a classical immune stimulus relative to well-matched comparators. 3) Determine if LPS differentially alters cognitive function, subjective response, or physiological markers in individuals with PTSD compared to well-matched comparators. Hypothesis: Individuals with PTSD will exhibit a suppressed neuroimmune system at baseline and an attenuated neuroimmune response following LPS challenge, relative to matched trauma controls.