Sex differences in [(11)C]ABP688 binding: a positron emission tomography study of mGlu5 receptors

PURPOSE: The purpose of this study was to assess, in a large sample of healthy young adults, sex differences in the binding potential of [(11)C]ABP688, a positron emission tomography (PET) tracer selective for the metabotropic glutamate type 5 (mGlu5) receptor. METHODS: High resolution [(11)C]ABP688 PET scans were acquired in 74 healthy volunteers (25 male, 49 female, mean age 20 ± 3.0). Mean binding potential (BP(ND) = f(ND) * (B(avail) / K(D))) values were calculated in the prefrontal cortex, striatum, and limbic regions using the simplified reference tissue model with cerebellar grey matter as the reference region. RESULTS: [(11)C]ABP688 BP(ND) was significantly higher in men compared to women in the prefrontal cortex (p < 0.01), striatum (p < 0.001), and hippocampus (p < 0.05). Whole-brain BP(ND) was 17% higher in men. BP(ND) was not related to menstrual phase in women. CONCLUSIONS: Binding availability of mGlu5 receptors as measured by PET [(11)C]ABP688 is higher in healthy men than women. This likely represents a source of variability in [(11)C]ABP688 studies and could have relevance for sex differences in cognitive-behavioral functions and neuropsychiatric disorders.