SPECT [I-123]iomazenil measurement of the benzodiazepine receptor in panic disorder

Background: Alterations in benzodiazepine receptor function have long been hypothesized to play a role in anxiety. Animal models of anxiety involving exposure to chronic stress have shown a specific decrease in benzodiazepine receptor binding in frontal cortex and hippocampus. The purpose of this study was to examine benzodiazepine receptor binding patients with panic disorder and comparison subjects. Methods: A quantitative measure related to benzodiazepine receptor binding (Distribution Volume (DV)) was obtained with single photon emission computed tomography (SPECT) imaging of [ 123I]iomazenil and measurement of radioligand concentration in plasma in patients with panic disorder and healthy controls. DV image data were analyzed using statistical parametric mapping (spm96). Results: A decrease in measures of benzodiazepine receptor binding (DV) was found in left hippocampus and precuneus in panic disorder patients relative to controls. Panic disorder patients who had a panic attack compared to patients who did not have a panic attack at the time of the scan had a decrease in benzodiazepine receptor binding in prefrontal cortex. Conclusions: Findings of a decrease in left hippocampal and precuneus benzodiazepine receptor binding may be related to alterations in benzodiazepine receptor binding, or other factors including changes in GABAergic transmission or possible endogenous benzodiazepine compounds. Benzodiazepine receptor function in prefrontal cortex appears to be involved in changes in state-related panic anxiety.