Cover legend: Striatal neurons, taken from BAC D₂-eGFP transgenic mice in order to identify those cells expressing the dopamine 1 or 2 receptor (D₁ or D₂), were filled with biocytin and reconstructed to examine dendritic branching patterns and total dendritic arbor. The red, pink, yellow, and orange neurons are D₁ medium spiny neurons, which have a larger dendritic arbor as compared to D₂ medium spiny neurons (blue, purple, teal, and light blue). These anatomical differences contribute to differences in excitability seen electrophysiologically. A GABAergic interneuron (white) is included for comparison. For more information, see the article by Gertler et al. in this issue (pages 10814–10824).