Immunoelectron microscopy demonstrating somatodendritic expression of DAGLα in spines, dendritic shafts, and somata of medium spiny neurons. Black arrows and arrowheads indicate asymmetrical or symmetrical synapses, respectively. A, B, Immunoperoxidase showing spotty labeling for DAGLα (open arrows) in spines (Sp), shaft dendrites (Dn), and perikarya (Pe) of presumed MS neurons. C–G, Silver-enhanced immunogold showing preferential cell surface distribution of DAGLα in spine head and neck, shaft dendrites, and somata of presumed MS neurons. H, The mean number of metal particles for DAGLα per 1 μm of the cell membrane. From very low density in nerve terminals, DAGLα is judged to be distributed selectively in somatodendritic compartments. Numbers in parentheses indicate the total length of measured cell membrane. NT, Nerve terminal; Nu, nucleus. Scale bars: A–C, F, G, 500 nm; D, E, 250 nm.