Serotonin 1A receptor availability in patients with schizophrenia and schizo-affective disorder: A positron emission tomography imaging study with [¹¹C]WAY 100635

Background: Postmortem and positron emission tomography (PET) studies have reported several alterations in serotonin 1A receptor (5-HT_1A) binding parameters in patients with schizophrenia. This study examines 5-HT _1A availability in vivo in individuals with schizophrenia and schizo-affective disorder. Materials and methods: Twenty-two medication-free individuals with schizophrenia or schizo-affective disorder and 18 healthy subjects underwent PET scans with [¹¹C]WAY 100635. Regional distribution volumes (V _T, in milliliters per gram) were derived using a two-tissue compartment kinetic model. Outcome measures for 5-HT _1A availability included binding potential (BP) and the specific to nonspecific equilibrium partition coefficient (V _3″). Eleven brain regions with high density of 5-HT_1A were included in the analysis. Results: No significant differences were observed in regional BP or V _3″ between patients and controls. No significant relationships were observed between regional 5-HT_1A availability and symptom severity. Conclusion: The postmortem literature reports increased 5-HT _1A binding in the prefrontal cortex in schizophrenia. This study did not detect differences in 5-HT_1A binding. Whereas in two recently published PET studies, one reports increased binding in the temporal lobe while the other reports decreased binding in the amygdala. These inconsistencies suggest that the alterations demonstrated in postmortem studies cannot be reliably detected at the resolution achieved with PET. This raises the question as to whether major changes in the level of expression of the 5-HT_1A receptor play a role in the pathophysiology of schizophrenia.