“The role of the cannabinoid (CB) system in the tolerance to analgesic effect of opioid remains obscure. The aim of the present study was to evaluate the effects of the endocannabinoid nonselective receptor agonist anandamide (AEA) and CB1 receptor antagonist rimonabant (SR141716) on morphine analgesia and tolerance in rats.
The findings suggested that AEA in combination with morphine produced a significant increase in expression of analgesic tolerance to morphine.
Conversely, cannabinoid receptor antagonist SR141716 attenuated morphine analgesic tolerance.
In addition, administration of AEA with morphine increased morphine analgesia.
In conclusion, we observed that the cannabinoid receptor agonist anandamide and CB1 receptor antagonist SR141716 plays a significant role in the opioid analgesia and tolerance.”