Effect of pretreatment with various antagonists on the GP rCBF response to U91356a. In each graph, control experiments (mean ± SEM) are represented by filled circles and antagonist pretreatment experiments are represented by hollow squares. Top left, eticlopride (D2antagonist, 4 mg/kg); top right, SCH23390 (D1 antagonist, 1 mg/kg); bottom left, ketanserin (5HT2 antagonist, 0.6 mg/kg); bottom right, domperidone (peripheral D2 antagonist, 0.1 mg/kg).