Differentiation of Non-Pharmacological from Pharmacological Dopamine Release in the Living Human Brain

This review depicts characteristics of nuclear neuroimaging investigations of dopamine release in response to non-pharmacological stimuli. Investigations of dopamine release in response to pharmacological challenges have focused mainly on the striatum, a region with a relatively high density of dopamine D2/D3 receptors. Non-pharmacological stimuli likely elicit dopamine release in extrastriatal regions with a relatively low density of dopamine D2/D3 receptors. Several strategies will facilitate the optimal design of investigations of dopamine release in response to non-pharmacological stimuli. (1) Employ radioligands with relatively high affinities for dopamine D2/D3 receptors in extrastriatal regions, including [11C] FLB457 and [11C] fallypride. (2) Correct images for head movement during the scanning procedure. (3) Develop protocols to incorporate the influences of regional blood flow on scans of dopamine D2/D3 receptors in the striatum and in extrastriatal regions. (4) Recruit healthy adults aged 18 to 35 years to avoid the effects of ageing. (5) Identify the phase of the menstrual cycle for women to account for the normal alterations in dopamine release in the various hormonal stages. Utilization of novel techniques to quantitate the dopamine release in the appropriate extrastriatal regions will likely result in fruitful advances in knowledge about non-pharmacological alternative interventions including acupuncture, the external Qi of Yan Xin Qigong, and other therapies of traditional Chinese medicine. Neuroimaging investigations of dopamine release following these alternative treatments will likely facilitate the appropriate application of alternative treatments to a vast spectrum of nervous and mental diseases. Since the effects of dopamine release on drug and non-drug interventions are powerful tools to assess the pathophysiology and the treatment of neuropsychiatric disorders, we provide this review of the literature to guide future research.