Research and exploration of the human brain and the structures that are part of it have been constant since antiquity. The neuron as the basic unit of the nervous system has been specially investigated, employing strategies such as the use of different stains to observe its structure.

The German neurologist Franz Nissl elaborated a stain based on dyes such as toluidine blue or cresyl violet, and before its application he could observe how this substance clearly showed the existence of different structures in the neuronal cytoplasm. What we know today as corpuscles or Nissl bodies had been discovered.

Nissl’s bodies: what are they?

The Nissl or ergastoplasmic bodies are small structures in the form of corpuscles or granules present in the neurons of the nervous system. These structures are found in the cytoplasm of the cell, and are located in specific parts of the neuron. They can be found especially in the soma or nucleus of the neuron and also in dendrites, not being found in the neuronal axon.

Nissl bodies are considered clusters of rough endoplasmic reticulum . In other words, they are structures formed by parallel cisterns with ribosomes (enzymatic structures made of ribosomal RNA) attached in a spiral, in which free polyribosomes can also be seen. These bodies only appear in eukaryotic cells, i.e. those that have a nucleus like neurons, and have the function of secreting proteins.

They are also basophilic structures, characterized by the affinity and ease of staining by dyes. In these structures there is a high concentration of both ribosomal and messenger RNA , with the active ribosomes being linked to the latter.

They can be of different sizes and come in different quantities depending on the type of neuron. Those in the ganglia of the autonomic nervous system tend to be small, while other large neurons tend to have larger Nissl bodies.

Function of these structures

The Nissl bodies, as clusters of rugged endoplasmic reticulum in which ribosomes are observed and in which both ribosomal and messenger RNA can be found, have as their main function the synthesis and transport of proteins inside the cell. Specifically, the part of the Nissl bodies that are most active in generating proteins for use inside the cell are the free polyribosomes.

The proteins secreted by these bodies are essential for transmitting nerve impulses between neurons , as well as participating in the generation of neurotransmitters.

In addition, the Nissl body plays an important role in maintaining the health of the cell by allowing the regeneration of structures damaged by the neuron’s own activity or by external factors.

Chromatolysis as a defense to neuronal damage

Nissl bodies can be damaged by possible injuries or pathologies. Neural damage such as that caused by trauma and disease can lead to damage to the axon.

The presence of damage to the axon causes the neuron to react by swelling and moving the nucleus away from the injury. It also acts by giving a response called chromatolysis, in which Nissl bodies move from the neuronal cytoplasm to the injured area in order to repair it. Reorganization and regeneration of the axon is allowed, so that the neuron’s functionality is recovered, but while this occurs the Nissl bodies dissolve . Fortunately, if the recovery of the neuron is achieved, chromatolysis ceases and the cytoplasm can recover and form new bodies.

This reaction can appear as we have said in injuries caused by trauma, but it has also been observed in various disorders. It is common to observe its appearance in neurodegenerative processes such as dementia due to Pick’s disease or Alzheimer’s (in fact, the changes in cytoplasm that cause this event are usually considered as a sign of neuronal degeneration, so its occurrence may be a possible sign of danger), in Wernicke’s encephalopathy of Wernicke-Korsakoff syndrome, diseases such as porphyria or some infectious diseases. It can also be observed in normative aging or in situations of great continuous stress for the individual.

Bibliographic references:

  • Gómez, M. (2012). Psychobiology. Manual CEDE de Preparación PIR.12. CEDE: Madrid-
  • Ramón y Cajal, S. (2007). Histology of the nervous system of man and vertebrates. Volume i. Ministry of Health and Consumer Affairs. Madrid.