Assessment of Toxicity and Biological Effects of α-Pinene on Morphine Tolerance and Dependence in Mice

Background: Research shows that α-Pinene interacts with the opioidergic system. Objectives: This study aims to examine the toxicity and the effects of α-Pinene on morphine tolerance and dependence in mice. Methods: Guidelines No. 423 and No. 407 were used to investigate acute and sub-chronic toxicity, respectively. For sub-chronic toxicity analysis, the animals were sacrificed on day 28, and blood and tissue samples were collected. After inducing morphine tolerance or dependence, in both phases, animals received i.p. vehicle, diazepam (5 mg/kg), and α-Pinene (3.125, 6.25, and 12.5 mg/kg). Withdrawal signs were recorded for 30 minutes. Results: Only the acute dose of α-Pinene showed mortality in animals, but mild lesions were seen in the brain, liver, and kidneys in the mice receiving its subchronic dose. Moreover, ALT, AST, ALP, and TG levels increased (P < 0.05) in female mice. Besides, 6.25 and 12.5 mg/kg (P < 0.001) of α-Pinene and only its high dose (12.5 mg/kg) (P < 0.001) reduced the number of jumps in the tolerance and dependence phases, respectively. Diarrhea (P < 0.001), writhing (P < 0.001), rearing, and climbing (P < 0.05 and P < 0.001, respectively) behaviors decreased in the tolerance phase, and grooming, climbing, and teeth chattering declined in the dependence phase (P < 0.001). Conclusions: The LD50 of α-Pinene was lower than 2000 mg/kg, but its subchronic dose caused mild tissue toxicities and biochemical changes. Moreover, α-Pinene decreased morphine tolerance and dependence and possibly was useful for the treatment of opioid dependence after complimentary trials.