The Effect of Cannabidiol on Nociceptive Behaviour and the Endocannabinoid System in an Incisional Wound Model

TL;DR

This study shows that cannabidiol (CBD) can reduce wound-related pain in rats, but its effects are limited and do not involve major changes in the endocannabinoid system.

Contribution

The study provides new evidence for CBD's antinociceptive effects in an incisional wound model and identifies specific brain region changes.

Findings

CBD (3 mg/kg) partially reduced primary mechanical hypersensitivity in the dorsum.

CBD did not affect secondary mechanical hypersensitivity or endocannabinoid levels in plasma or most brain regions.

CBD altered 2-AG and AEA levels in specific brain regions, suggesting localized effects.

Abstract

Background/Objectives: Wound-related pain is a common, yet inadequately managed condition, and new therapeutic strategies are warranted. Limited data suggests that phytocannabinoids and cannabis may alleviate wound-related pain; however, further studies are required. This study investigated the effects of systemic administration of cannabidiol (CBD) on nociceptive behaviour following dorsum incision and on the endocannabinoid system. Methods: Male Sprague-Dawley rats (150–200 g on arrival, n = 9/group) underwent a 1.2 cm incision on the hairy skin of the dorsum or sham procedure. Back and hind paw mechanical withdrawal thresholds were assessed at baseline and post-surgery/sham days (PSDs) 1, 4, 7, and 8 using manual and electronic von Frey tests, respectively. On PSD 8, the effect of a single acute administration of CBD (3, 10, or 30 mg/kg, i.p.) on mechanical hypersensitivity in the dorsum and hind paws was assessed. The levels of endocannabinoids and N-acylethanolamines in the plasma and discrete brain regions following CBD administration were analysed. Results: Robust mechanical hypersensitivity was evident in the dorsum and hind paws following the incision. CBD (3 mg/kg) partially attenuated primary mechanical hypersensitivity in the dorsum, in a site- and dose-specific manner. CBD had no effect on secondary mechanical hypersensitivity. CBD did not alter the levels of endocannabinoids or N-acylethanolamines, but in rats that received CBD (3 mg/kg), levels of 2-AG were lower in the contralateral amygdala and levels of AEA were higher in the contralateral lumbar spinal cord, compared to the ipsilateral sides. Conclusions: These data provide evidence for antinociceptive effects of CBD in a model of incisional wound-related pain. Further research on CBD’s mechanism(s) of action is warranted. The potential antinociceptive effects of other phytocannabinoids in this model should also be investigated.

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