The main function of Nissl bodies within neurons is to aid in the production and dispersal of chemical substances such as proteins and peptides, as illustrated by Richard F. Thompson in his book "The Brain: A Neuroscience Primer." The structure of Nissl bodies makes them particularly adept at protein synthesis, an essential cellular process within a neuron.
The structure of Nissl bodies consists of a granular and concentrated section of the endoplasmic reticulum. The Nissl substance that creates the bodies is made up of RNA, proteins, lipids and acid polysaccharides that aid in the creation of proteins. It is believed that the majority of proteins created by Nissl bodies are used intercellularly.
Since Nissl bodies are found only in the soma and dendrites of a neuron and do not appear in the axon, the proteins they create are likely carried to the axon by axontransmitters. Nissl bodies are essential to the well-being of a neuron; a decrease in the number of Nissl bodies in a neuron indicates neural degeneration.
These structures change abruptly in the case of inflammatory disease, oxygen deprivation or trauma to the nervous system. They are named after the German scientist, F. Nissl, who first developed the technique of staining and identifying the structures with methylene blue.