Figure 5.

Distribution of DGL-α is highly compartmentalized on the head of the dendritic spines. A, B, Spatial distribution of immunogold particles representing DGL-α in relation to glutamate release sites on spine heads (n = 300) of hippocampal CA1 pyramidal cells in the stratum radiatum. The distance of immunogold particles from the edge of the synaptic junction (position 0, indicated by arrows) was measured along the plasma membrane, which was divided into 60 nm bins. Data are expressed as the percentage of immunogold particles in a given bin compared with all gold particles found in the spines. In A, the core dataset is illustrated, whereas in B, the same dataset was normalized to the frequency of given membrane compartments within the same spine population. The measurements demonstrate that DGL-α is preferentially targeted to a perisynaptic ring around the synaptic specialization but almost entirely excluded from the synapse itself. Besides a perisynaptic pool, the distribution of extrasynaptic DGL-α shows a clear gradient, decreasing toward the spine neck.