1. ¹Research Centre—Military Mental Healthcare, Ministry of Defense, Utrecht, The Netherlands
2. ²Department of Psychiatry, Rudolf Magnus Institute of Neuroscience, Utrecht University Medical Centre, Utrecht, The Netherlands
3. ³Department of Nuclear Medicine & PET Research, VU University Medical Centre, Amsterdam, The Netherlands

Correspondence: Dr E Geuze, Research Centre—Military Mental Healthcare, Ministry of Defense, PO Box 90.000, 3509 AA Utrecht, The Netherlands. E-mail: s.g.geuze@umcutrecht.nl

Received 10 August 2006; Revised 2 May 2007; Accepted 7 May 2007; Published online 31 July 2007.

Abstract

-Aminobutyric acid (GABA_A) receptors are thought to play an important role in modulating the central nervous system in response to stress. Animal data have shown alterations in the GABA_A receptor complex by uncontrollable stressors. SPECT imaging with benzodiazepine ligands showed lower distribution volumes of the benzodiazepine-GABA_A receptor in the prefrontal cortex of patients with post-traumatic stress disorder (PTSD) in one, but not in another study. The objective of the present study was to assess differences in the benzodiazepine-GABA_A receptor complex in veterans with and without PTSD using [¹¹C]flumazenil and positron emission tomography (PET). Nine drug naive male Dutch veterans with deployment related PTSD and seven male Dutch veterans without PTSD were recruited, and matched for age, region and year of deployment. Each subject received a [¹¹C]flumazenil PET scan and a structural magnetic resonance imaging scan. Dynamic 3D PET scans with a total duration of 60 min were acquired, and binding in template based and manually defined regions of interest (ROI) was quantified using validated plasma input and reference tissue models. In addition, parametric binding potential images were compared on a voxel-by-voxel basis using statistical parametric mapping (SPM2). ROI analyses using both template based and manual ROIs showed significantly reduced [¹¹C]flumazenil binding in PTSD subjects throughout the cortex, hippocampus and thalamus. SPM analysis confirmed these results. The observed global reduction of [¹¹C]flumazenil binding in patients with PTSD provides circumstantial evidence for the role of the benzodiazepine-GABA_A receptor in the pathophysiology of PTSD and is consistent with previous animal research and clinical psychopharmacological studies.