What are glia? An what have they got to do with pain?
To put it simply glia are connective cells that line and modulate your central nervous system. The central nervous system comprises of all the cells of our brain and spinal cord. Within the central nervous system, trillions of neurons (nerve cells) communicate messages between each other. These messages are always responding to our external environment and say 'all is well' or 'something is off, protect'!
Of course, being the body, this is all done chemically, both through the release of messenger proteins (neurotransmitters) and signalling molecules (neuropeptides).
And it is this heightened neural communication system occurring within our brains that creates the output of pain.
Ok great you might be thinking. But where do glia fit into all of this?
There are three primary types of glia associated with the central nervous system (where pain sensations are produced)
Microglia = Located throughout the central nervous system, comprising 10-15% of all cells. They modulate efficiency of communication between neurons by releasing another kind of signalling protein called cytokines.
Astrocytes = wrap around the space in which neurons communicate via neurotransmitters
Oligodendrocytes = wrap around the axons (communication strands) of neurons
We can think about these cells as insulating our neurons. Letting them know whether they need to increase or decrease signalling in response to overall threat level.
Glia seem to respond to any prolonged state of emotional or psychological threat we might be detecting, releasing their own set of messenger proteins . Those proteins then activate receptors on neurons which in turn amplifies or tunes down the danger messages being sent to the brain.
The takeaway is that glial cells respond to threat or chronic stress, releasing peptides that stimulate our central nervous system. This creates increases in signal transmission and danger perception.
I think glia will be an even more hot topic in the next 20 years or so and rightly so.
Bolton et al. 2023. Stressed Microglia: Neuroendocrine–Neuroimmune Interactions in the Stress Response. Endocrinology. 164 ://academic.oup.com/endo/article/164/7/bqad088/7190275?login=false
Jauregui-Huerta, F. et al. (2010). Responses of Glial Cells to Stress and Glucocorticoids. Current immunology reviews. 6. 195-204. 10.2174/157339510791823790.
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