Pain is not just a Matter of Nerves

There are a few different types of glia in the brain: oligodendrocytes, microglia, and astrocytes. Each is needed to optimize brain function. Oligodendrocytes are specialized cells that wrap tightly around axons to form the myelin sheath. These cells speed up the electrical signals (action potentials) that travel down an axon. Without oligodendrocytes, an action potential would travel down an axon 30 times slower!

The sensation of pain occurs when neural pathways conduct excitation generated by tissue damage to the spinal cord, where the nociceptive information is pre-processed. From there, the information is transmitted to the brain, where the sensation of “pain” is finally created. This is the general belief. However, researchers from the Division of Neurophysiology at MedUni Vienna’s Center for Brain Research have now discovered that pain is not just a matter of nerves but that non-neuronal cells, the glial cells, are also involved in clinically relevant pain models and their activation is sufficient to amplify pain.

Glial cells are the commonest type of cells in the human brain and spinal cord. They surround neurons but are distinct from them and play an important supporting role – eg in material transport and metabolism or the fluid balance in the brain and spinal cord. At the same time, however, when they are activated – by pain processes, for example – glial cells are themselves able to release inflammatory cytokines etc. Glial cells therefore have two modes: a protective and a pro-inflammatory mode. “The activation of glial cells results in a pain-amplifying effect, as well as spreading the pain to previously unaffected parts of the body. For the very first time, our study provides a biological explanation for this and for other hitherto unexplained pain phenomena in medicine,” says Jürgen Sandkühler, Head of the Division of Neurophysiology at MedUni Vienna’s Center for Brain Research.

Over-activation of glial cells in the spinal cord can, for example, be caused by strong pain stimuli from a wound or surgical intervention, or even by opiates. Sandkühler: “This could also explain why opiates are initially very good at relieving pain but then often cease to be effective. Another example is the phenomenon of “withdrawal” in drug addicts, where activated glial cells cause severe pain throughout the body.”

Neuroinflammatory diseases of the brain, environmental factors and even the person’s own lifestyle can lead to activation of glial cells. Eg depression, anxiety disorders and chronic stress, MS or Alzheimer’s and diabetes, as well as lack of exercise and poor diet. Improvements in a person’s lifestyle could have a beneficial impact upon this system and ensure that they generally suffer less pain or “minor niggles,” says Sandkühler: “It is therefore in our own hands: 30 minutes of moderate exercise three or four times a week, a healthy diet and avoiding putting on excess weight can make a huge difference.” http://www.alphagalileo.org/ViewItem.aspx?ItemId=169847&CultureCode=en