Abstract
Cannabidiol, a major non-psychoactive constituent of cannabis, has
generated interest as a novel therapeutic for managing several
pathological conditions including chronic pain and opioid use disorder.
Here, we evaluated the effects of cannabidiol (3.2 or 10.0 mg kg-1) on
the antinociceptive and the reward-related effects of the opioid
analgesic oxycodone (0.56 mg kg-1) in rats using an operant pain assay,
locomotor activity monitoring, and the conditioned place preference
paradigm. We also assessed pharmacokinetic and pharmacodynamic
interactions between cannabidiol and oxycodone in plasma and brain.
Cannabidiol enhanced the antinociceptive effect of oxycodone without
affecting oxycodone-induced behavioral sensitization, or the acquisition
and expression of oxycodone conditioned place preference. Cannabidiol
coadministration with oxycodone reduced levels of the oxycodone
metabolite noroxycodone in the plasma and increased levels of oxycodone
in the brain, while oxycodone coadministration increased levels of the
cannabidiol metabolite 7-carboxycannabidiol in plasma. Rats that
received oxycodone generally showed higher levels of biogenic amines
across the brain, whereas those administered cannabidiol alone or
oxycodone plus cannabidiol showed similarly lower levels. This indicates
coadministration of cannabidiol has central neurochemical actions
distinct from administration of oxycodone alone. Together, these
findings suggest that cannabidiol potentiates the analgesic effects of
oxycodone without affecting its reward-related properties, and this
dichotomy appears to be due to complex pharmacological interactions
between cannabidiol and oxycodone in the brain. As such, cannabidiol may
hold promise as an opioid sparing approach to managing pain.