Reduced amygdala serotonin transporter binding in posttraumatic stress disorder

Area of Science:

• Neuroscience
• Psychiatry
• Radiochemistry

Background:

• The amygdala plays a crucial role in stress response regulation.
• Dysfunctional serotonin transporter (5-HTT) and amygdala activity are implicated in posttraumatic stress disorder (PTSD) pathophysiology.
• Previous studies have not evaluated 5-HTT in humans with PTSD.

Purpose of the Study:

• To investigate amygdala 5-HTT expression in individuals with PTSD using positron emission tomography (PET).
• To test the hypothesis that PTSD patients exhibit reduced amygdala 5-HTT availability.
• To explore the relationship between amygdala 5-HTT binding and anxiety/depression symptom severity.

Main Methods:

• PET scans were performed on 15 participants with PTSD and 15 healthy controls (HC).
• A selective 5-HTT radiotracer, [(11)C]AFM, was used to measure 5-HTT binding potential (BP(ND)).
• Resting-state scans were conducted to assess amygdala 5-HTT availability.

Main Results:

• PTSD group showed significantly reduced amygdala [(11)C]AFM BP(ND) compared to HC (16.3% reduction).
• The left amygdala exhibited a more pronounced reduction in [(11)C]AFM BP(ND) in the PTSD group (20.5% reduction).
• Amygdala [(11)C]AFM BP(ND) was inversely correlated with Hamilton Rating Scale for Anxiety and Montgomery-Åsberg Depression Rating Scale scores.

Conclusions:

• Reduced amygdala 5-HTT binding is observed in individuals with PTSD.
• These findings support a translational neurobiological model of PTSD.
• Dysregulated 5-HTT signaling in the amygdala may contribute to threat detection and fear learning deficits in PTSD.