Repeated Tetrahydrocannabinol Injections Induce Tolerance but Do Not Disrupt Ongoing Behaviour Upon Withdrawal in Male and Female Rats With Inflammatory Pain.
European journal of pain (London, England) May 1, 2026 Michael M Morgan, Christa M Hickey
Inflammatory pain, induced by CFA injection in rats, reduced wheel running. Twice-daily THC injections (3 mg/kg) further decreased running in both sexes, with tolerance developing more strongly in males. No spontaneous withdrawal was observed over six days, nor any effect on body weight. The absence of withdrawal contrasts with previous opioid findings where pain enhanced morphine withdrawal. Persistent inflammatory pain does not alter the effects of repeated THC in male or female rats; THC's use for pain is limited by side effects and tolerance but not by dependence-related withdrawal.