[123I]Iomazenil SPECT benzodiazepine receptor imaging in schizophrenia

Area of Science:

• Neuroscience
• Psychiatry
• Radiology

Background:

• Postmortem studies suggest reduced gamma-aminobutyric acid (GABA) neurotransmission in schizophrenia.
• In vivo studies on GABA(A)-benzodiazepine receptor (BZR) distribution in schizophrenia have yielded conflicting results.
• Previous in vivo investigations utilized smaller sample sizes, limiting definitive conclusions.

Purpose of the Study:

• To investigate regional changes in GABA(A)-benzodiazepine receptor (BZR) distribution volume (V3-p) in schizophrenia using a larger cohort.
• To explore the relationship between BZR V3-p and clinical variables, including symptom severity and illness duration.

Main Methods:

• Single photon emission computed tomography (SPECT) with [123I]iomazenil was employed.
• A constant infusion paradigm measured BZR V3-p under sustained radiotracer equilibrium.
• Statistical parametric mapping (SPM96) analyzed differences between 25 schizophrenia patients and 24 healthy controls, and correlations with PANSS scores.

Main Results:

• No significant differences in absolute BZR V3-p were found between patients and controls.
• A global normalization procedure revealed significantly decreased relative BZR V3-p in the left precentral gyrus (BA 6) of patients.
• Relative BZR V3-p positively correlated with duration of illness in the superior occipital gyri (BA 19); no correlations with age or PANSS scores were observed.

Conclusions:

• A decrease in relative BZR V3-p in the left precentral gyrus suggests regional alterations in GABAergic neurotransmission in schizophrenia.
• The positive correlation with illness duration may indicate relative preservation of BZR-expressing neurons in certain cortical areas over time.
• Findings highlight the importance of normalization methods in detecting subtle regional differences in BZR availability in vivo.