Ultrahistochemical demonstration of guanylate cyclase activity in the rat hippocampus.

Guanylate cyclase activity was demonstrated in the rat hippocampus at the electron microscopy level by a cerium precipitation technique. Enzymatic activity is localized in the granular cells of the dentate gyrus and in other, medium-sized neurons. The reaction product was found on the cytoplasmic membrane, in the cytoplasm, on the surface of endoplasmic reticulum and in postsynaptic densities. Glial cell processes and small dendritic processes were also stained. Besides the neurons, glial cells contained strong enzymatic activity, especially the perivascular glia and protoplasmatic glial cells neighbouring to neurons. Only little activity was detected in pyramidal cells and no activity was found in the endothelium cells of capillaries.