Measurement of Brain Gaba-Benzodiazepine Receptor Levels In Vivo Using Emission Tomography

Knowledge about the neurobiology of the brain is fundamental to our understanding of neuropsychiatric disorders. There are a number of different approaches that have been successfully used to investigate brain function in neuropsychiatric disorders and to inform development of treatment strategies. These have involved animal models, human postmortem studies, measures of neurotransmitters and their metabolite levels in blood, cerebrospinal fluid (CSF), or urine, and neuroendocrine or physiological challenges. All these have severe limitations, as they are surrogate measures. Animal models of human brain function and pathology are inevitably limited by phylogenetic differences. There are inherent problems in using post-mortem tissue, such as antemortem medical complications and tissue instability after death. It is also hard to disentangle whether any changes seen are primary or secondary to the disease or to the treatment received. Although the other three approaches are in vivo and overcome some of these difficulties, it can be problematic to interpret the results with regard to a single neurotransmitter system or to changes in a discrete neuroanatomical location.