Chapter 27: Molecular imaging of serotonin synthesis in the brain

Abstract

Tracer kinetic analysis of 11 C-labeled alpha-methyl-tryptophan (AMT) allows quantitative assessment of serotonin synthesis using positron emission tomography (PET) imaging in human brain. The obtained K-complex represents an index of serotonin synthesis (termed serotonin synthesis capacity) that is well suited to study serotonergic mechanisms in the developing brain. Assessment of global and local developmental changes of serotonin synthesis capacity in brains of autistic children indicates impaired serotonin metabolism that affects neuronal differentiation of serotonergic neurons during critical developmental periods. Moreover, increased serotonin synthesis capacity in various supratentorial regions of children with alternating hemiplegia is observed during ictal and postictal periods, suggesting increased regional serotonergic activity associated with hemiplegic attacks in extended neural networks. Finally, children with Tourette syndrome show decreased serotonin synthesis capacity in the bilateral dorsolateral prefrontal cortex and increased serotonin synthesis capacity in the bilateral thalamus and caudate, suggesting abnormal tryptophan metabolism in the fronto-striato-thalamic circuits.