DA receptor-mediated modulation is heterogeneous. Bubble plot of spatial distribution of varicosities and magnitude of DA receptor-mediated modulation in wild type and D2 and D3 KO mice. The distance of imaged varicosities from the soma is indicated along the x-axis. Bubble area is proportional to the magnitude of modulation. Facilitation is shown in red and inhibition in purple. In experiments two experiments, both SKF81297 and quinpirole were tested sequentially in the same cell (experiments 8 and 12). In experiment 8 (data shown in Figure 3), the majority of varicosities showed both D1 receptor-mediated facilitation and D2 receptor-mediated inhibition, but the magnitude of modulation varied strikingly among individual varicosities. In experiment 12, in a D3 KO mouse, the third varicosity showed both SKF81297-mediated facilitation and quinpirole-mediated inhibition, indicating colocalization of D1 and D2 receptors.