Scientists have recently discovered that psilocybin, the active ingredient in “magic mushrooms,” can significantly reduce chronic pain in rats. Notably, this pain relief was related to pain from touch, but not pain from heat. The study was published in Current Biology.
Psychedelic drugs have recently gained attention for their potential to treat various psychiatric disorders. Psilocybin, in particular, has been the subject of research for its therapeutic effects on treatment-resistant depression as well as alcohol and tobacco abuse.
Led by Nicholas Kolbman, researchers from the University of Michigan set out to explore the possibility of psilocybin as a treatment for chronic pain, an area that had not been systematically studied before despite the growing evidence for it.
The team utilized a rat model where chronic pain was induced using intravenous formalin injections, which is a compound known to cause long-lasting pain sensitivity. In this study, two types of pain responses were analyzed.
Mechanical hypersensitivity, which is increased sensitivity to pain from physical touch that wouldn’t normally be painful, was measured in the rats using a device known as von Frey filaments. These tools contained thin, flexible hairs of different thicknesses that were pressed against the rats’ paws until they were bent.
Thermal hyperalgesia was also measured, which occurs when intense pain is experienced from warm temperatures that would not usually be painful. This pain response was determined by measuring how quickly the rats withdrew their paw after being placed on a hot surface (126.5°F/52.5°C).
Kolbman and colleagues then administered different doses of psilocybin to the rats and then observed the effects on pain sensitivity.
13 rats (6 male, 7 female) were provided saline solution, 14 rats (6 male, 8 female) were given a low psilocybin dose of 1 mg/kg, and 12 rats (6 male, 6 female) were provided a high psilocybin dose of 10 mg/kg.
Pain responses to the touch and heat stimuli were measured a few hours after formalin infusion, every second day during the first week, and then weekly over the next three weeks.
The study found that both the low and high doses of psilocybin significantly reduced mechanical hypersensitivity for all testing days, up to 28 days.
However, the drug had a limited effect on thermal hyperalgesia. The low dose only reduced pain on days 3, 5, and 21, and the high dose also briefly reduced pain on the day of administration and on day 5.
Kolbman’s team concluded, “Psilocybin could act via neuroplastic effects produced by psychedelics … psilocybin-induced attenuation of mechanical hypersensitivity outlasted the half-life of psilocybin (~2 h post intravenous administration), which suggests a centrally mediated mechanism of action.”
In other words, the pain relief lasted much longer than the time psilocybin stays in the body (the substance itself only lasts for about two hours after administration). This long-lasting effect implies that psilocybin is working through a central mechanism in the brain, not just at the local site of pain.
The researchers noted that this finding holds significance because many chronic pain conditions are believed to be due to changes in the brain and spinal cord, and psilocybin may help ‘rewire’ certain brain circuits involved in pain, providing relief that goes beyond the temporary effects of traditional pain medication.
While the study presents promising results, it also acknowledges limitations. The model used represents pain from chemical inflammation, which may not cover all types of chronic pain. Additionally, the study was not designed to compare the effects of psilocybin between male and female rats conclusively.
The study, “Intravenous psilocybin attenuates mechanical hypersensitivity in a rat model of chronic pain,” was authored by Nicholas Kolbman, Tiecheng Liu, Peter Guzzo, Jim Gilligan, George A. Mashour, Giancarlo Vanini, and Dinesh Pal.