Neurotransmitter visualization in schizophrenia

Abstract

Background: Although the history, interview, and examination of the patient provide the foundation for the diagnosis of schizophrenia, nuclear neuroimaging investigations constitute promising tools to elucidate the pathophysiology of schizophrenia and other neuropsychiatric disorders. Imaging studies of neuroreceptors constitute research tools to investigate the role of dysfunction of the acetylcholinergic, dopaminergic, glutamatergic, serotonergic, cannabinoid, opioid, and nicotinic systems in the pathogenesis and pathophysiology of schizophrenia and related conditions. People with the phenotype of the clinical syndrome of schizophrenia likely represent multiple distinct genotypes with poorly characterized biological traits. Thus, the population of people manifesting the clinical syndrome of schizophrenia likely contains several heterogeneous biological subgroups yet to be specified. The dopamine hypothesis of schizophrenia proposes that the positive symptoms result from an excess of intrasynaptic dopamine, an excitatory neurotransmitter, and the negative symptoms result from a deficit of intrasynaptic dopamine. Accordingly, a group of people with schizophrenia likely have reduced intrasynaptic dopamine in the tonic, resting, basal state, and increased intrasynaptic dopamine in the excited, aroused, phasic state. Additionally, the glutamate hypothesis of schizophrenia suggests that dysfunction of glutamate, another excitatory neurotransmitter, in the prefrontal region results in excessive concentrations of dopamine in the striata resulting in the positive symptoms of schizophrenia. Methodology/Principal Findings: Published research about the nuclear neuroimaging techniques to identify neurotrans- mitters in people with schizophrenia are reviewed. Conclusions/Significance: Future research including neuronuclear imaging and genetic evaluations is needed to characterize the biological subgroups of people with the clinical syndrome of schizophrenia. Neuronuclear imaging studies will likely refine the measurement of neurotransmitters in the presynaptic, synaptic, and postsynaptic regions in people with schizophrenia and healthy people. Imaging studies of neuroreceptors during the administration of putative therapeutic agents for schizophrenia will help determine the optimal dose. In the future the research findings summarized in this article will likely be translated into clinical practice.