Dopamine D-1 agonist activates temporal lobe structures in primates

Changes in the function of dopamine D-1-influenced neuronal pathways may be important to the pathophysiology of several human diseases. We recently de veloped methods for averaging functional imaging data across nonhuman prima te subjects; in this study, we apply this method for the first time to map brain responses to experimental dopamine agonists in vivo. Here we report t he use of positron emission tomography (PET) in seven normal baboons to mea sure the regional cerebral blood flow (rCBF) responses produced by an acute dose of the dopamine D-1 full agonist SKF82958. The most significant rCBF increases were in bilateral temporal lobe, including amygdala and superior temporal sulcus (6-17%, P< 0.001). Blood flow decreased in thalamus, pallid um, and pons (4-7%, P = 0.001). Furthermore the rCBF responses were dose-de pendent and had a half-life of similar to 30 min, similar to that reported for the drug's antiparkinsonian effects. Absolute whole-brain blood flow di d not change, suggesting that these local changes in rCBF reflect neuronal rather than direct vascular effects of the agonist. The prominent temporal lobe response to a D-1 agonist supports and extends our recent observations that levodopa produces prominent amygdala activation both in humans and in other primates. We speculate that levodopa may exert its known effects on mood in humans through increased amygdala activity, mediated in part by D-1 receptors.