Detection of sialic acid residues in the axonal reticulum of rat superior cervical ganglion cells by lectin-gold cytochemistry

Abstract

Highly glycosylated compounds have been demonstrated in the axonal reticulum elements of the superior cervical ganglion cells of the rat, and this is considered to suggest a connection of the reticulum with the trans Golgi side. In the present study, the axonal reticulum and the Golgi elements were further characterized by post-embedding methods of lectin-gold cytochemistry to determine their carbohydrate residues and to see, more specifically, if sialic acid residues could be detected in the axonal reticulum elements. Therefore, the affinity of neuronal cell structures for Limax flavus agglutinin (LFA), wheat germ agglutinin (WGA), and Ricinus communis agglutinin I (RCA-I) was tested in ultra-thin sections of glycolmethacrylate-embedded material, counterstained with phosphotungstic acid (PTA) at low pH. The trans Golgi network, the Golgi-associated axonal reticulum, the reticulum within axons, the large dense-cored vesicles, and the plasma membranes were reactive for all three lectins used. We conclude that the axonal reticulum elements carry sialic acid residues, relating them to the trans Golgi network. The present results support the concept that the axonal reticulum is an extension of the trans network of the Golgi apparatus specialized for neurosecretion.