Electron microscopic cytochemistry of alkaline phosphatase in neurons of rats

Fine structural localization of alkaline phosphatase activity was studied in the neurons of the cerebral cortex and the optics and sciatic nerves of the rat by electron microscopic histochemistry with the lead citrate method. Most neurons in the cerebral cortex demonstrated alkaline phosphatase activity on the plasma membrane of the nerve cell body and dendritic processes, from the thick trunk to the terminal postsynaptic boutons. Alkaline phosphatase was also associated with the axolemma, but only at the terminal presynaptic boutons and at the nodal and paranodal region of the nodes of Ranvier. The axolemma covered by myelin sheaths did not show any activity. The alkaline phosphatase reaction of the Ranvier node could also be demonstrated in the optic and sciatic nerves.