Figure 4.

A, B, Histograms showing tangential distribution of cell membrane-associated immunogold particles for mGluR5 (A) and M₁ (B) on the spine head of medium spiny neurons. Immunoreaction was performed by preembedding silver-enhanced immunogold. The edge of postsynaptic density is defined as 0 with the synaptic and extrasynaptic side to the left and right, respectively. Note that the very perisynaptic region (0–40 nm bin, black columns) is provided with the highest labeling for mGluR5 but the lowest labeling for M₁ on the spine head. The total number of immunogold particles analyzed is 82 particles for mGluR5 and 69 particles for M₁. The total length of measured cell membrane is 36.0 μm for mGluR5 and 46.5 μm for M₁.