According to a new study published by the journal Cannabis and Cannabinoids Research, and published online by the National Institute of Health, topically-applied cannabinoids are effective in reducing corneal hyperalgesia (defined as a state of nociceptive sensitization caused by exposure to opioids) and inflammation.
“Corneal injury can result in dysfunction of corneal nociceptive signaling and corneal sensitization”, begins the study’s abstract. “Activation of the endocannabinoid system has been reported to be analgesic and anti-inflammatory.” The purpose of this research “was to investigate the antinociceptive and anti-inflammatory effects of cannabinoids with reported actions at cannabinoid 1 (CB1R) and cannabinoid 2 (CB2R) receptors and/or noncannabinoid receptors in an experimental model of corneal hyperalgesia.”
Below describes the methods used for this study:
Corneal hyperalgesia (increased pain response) was generated using chemical cauterization of the corneal epithelium in wild-type (WT) and CB2R knockout (CB2R-/-) mice. Cauterized eyes were treated topically with the phytocannabinoids Δ8-tetrahydrocannabinol (Δ8THC) or cannabidiol (CBD), or the CBD derivative HU-308, in the presence or absence of the CB1R antagonist AM251 (2.0 mg/kg i.p.), or the 5-HT1A receptor antagonist WAY100635 (1 mg/kg i.p.). Behavioral pain responses to a topical capsaicin challenge at 6 h postinjury were quantified from video recordings. Mice were euthanized at 6 and 12 h postcorneal injury for immunohistochemical analysis to quantify corneal neutrophil infiltration.
After conducting the study, researchers found that; “Topical cannabinoids reduce corneal hyperalgesia and inflammation. The antinociceptive and anti-inflammatory effects of Δ8THC are mediated primarily via CB1R, whereas that of the cannabinoids CBD and HU-308, involve activation of 5-HT1Areceptors and CB2Rs, respectively.”
The study concludes by stating that; “Cannabinoids could be a novel clinical therapy for corneal pain and inflammation resulting from ocular surface injury.”