Figure 3: Reversal of the morphine-induced tolerance by LASSBio-981 or amitriptyline. Morphine was infused (2.5 mg/kg/d, i.p.) through an osmotic mini-pump during 30 days. LASSBio-981 (10 mg/kg), amitriptyline (10 mg/kg) or vehicle was administered daily by gavage during 14 days after development of morphine tolerance. (•) LASSBio-981, (Δ) amitriptyline, (♦) vehicle. A) Latency in response to thermal stimulation in rats submitted to SNL. B) Withdrawal threshold in response to mechanical stimulation applied to the paw of rats submitted to SNL. Data represent the mean ± SEM (n = 4). *P<0.05 versus day 0; #P<0.05 versus day 7.