The endogenous opioid system refers to a network in our bodies that house occurring opioids, like endorphins (known as the “feel-good” chemical) and enkephalins (needed to maintain balanced brain function), alongside their receptors. The body naturally produces them in order to manage many physiological processes, like stress response, mood balancing, immune function, and more.
Components of this system contain the opioids themselves, their receptors, which help transfer their emitted signals to the brain. Enzymes are another component, and they are primarily needed to either break down active opioids or change molecules into active opioids (synthesis, or degradation). To tie everything together, the system is maintained by multiple “feedback” systems in order to comply with homeostasis. An example of feedback can include desensitizing opioid receptors if exposure to opioids is lengthy.
It’s important to have a basic understanding of the system in order to comprehend the role it plays into certain diseases. The endogenous opioid system is crucial to regulate pain perception, alongside other physiological processes. Therefore, it’s clear to see how dysfunction or deregulation of the system can result in inflammation and other medical conditions, thus being linked to multiple sclerosis. A study done by the departments of pharmacology, neuroscience and mental health, and anesthesiology at the University of Alberta further demonstrate this.
Glial cells, for instance microglia and astrocytes, are activated when chronically exposed to morphine, which can lead to increased regulation of proinflammatory cytokines and purinergic receptors (which moderate the stiffness of smooth muscles, like tracts). Instability of the endogenous opioid system in multiple sclerosis is particular through dead, build up-like concentration of opioid peptides, especially in human patient and animal models.
The study, alongside other preclinical studies, exhibits how small doses of naltrexone therapy can regulate immune responses, and improve symptoms of those with multiple sclerosis (clinical evidence is a bit mixed, however). By targeting the kappa receptors, which specifically are associated with dysphoria and stress response, remyelination in M.S. patients can be promoted. Dysfunction of the opioid system is usually the culprit of many common symptoms, including depression, chronic pain, and negative affect.
Opioid analgesics can provide relief, but it’s often inadequate as it depends on tolerance levels, which are varied amongst everyone. But ultimately targeting and understanding mechanisms relating to the endogenous opioid system can result in various new possibilities for therapies for disease progression within M.S.
Citations
Dworsky-Fried, Zoë, et al. “Multiple Sclerosis and the Endogenous Opioid System.” Frontiers in Neuroscience, vol. 15, Sept. 2021, https://doi.org/10.3389/fnins.2021.741503.
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