Rationale: Current perspectives on the pathophysiology of schizophrenia direct attention to serotonergic (serotonin, 5-HT) dysregulation in the prodrome or at-risk mental state (ARMS).
Objective: To study the cerebral 5-HT(2A) receptor (5-HT(2A)R) in the ARMS with [(18)F]altanserin positron emission tomography (PET) and a bolus-infusion paradigm.
Materials and methods: We quantified the spatial distribution of 5-HT(2A)R binding potential (BP(1)') in never-medicated subjects assigned to early (n = 6) and late (n = 8) prodromal states of schizophrenia relative to healthy controls (n = 21). Five single nucleotide polymorphisms (SNPs) in the 5-HT(2A)R-encoding gene (HTR2A; 13q14-21) were genotyped to control for a potential bias in BP(1)' due to between-group differences in genotype distributions.
Results: Group comparisons of partial-volume corrected PET data by statistical parametric mapping and confirmatory volume of interest analysis yielded a dissemination of BP(1)' decreases consistent with increasing levels of risk. An additional decrease in caudate BP(1)' was present in subjects who subsequently converted to first-episode psychosis (n = 5), but absent in non-converters (n = 9). Between-group differences were not confounded by a differential distribution of SNP genotypes.
Conclusion: These results suggest a progressive reduction of cortical 5-HT(2A)R density as a surrogate biological measure of increased risk for schizophrenia, irrespective of conversion. Progressive reductions of subcortical 5-HT(2A)R density could provide an indicator of illness activity and help to predict imminent conversion to schizophrenia. Moreover, our findings substantiate the rationale for establishing a phase-specific psychopharmacological intervention in the ARMS that addresses the serotonergic component of vulnerability to schizophrenia.