Effective
pain relief in animals relies on the ability to discern
pain and assess its severity. However, few objective measures exist to assess the presence and severity of
pain in axolotls, and few resources are available regarding drugs and appropriate doses to provide
pain relief in this species. This study evaluated behavioral tools for cageside
pain assessment and validated a reproducible and reliable quantitative method to evaluate
analgesic efficacy in axolotls. Animals were divided into control and treatment groups (n = 6 per group); treatment groups received
buprenorphine through injection (50 mg/kg every 24 h for 48 h intracelomically) or
butorphanol immersion (0.50 or 0.75 mg/L every 24 h for 48 h). Qualitative behavioral tests, adapted from other amphibian studies, included tapping on the home tank, directing water jets or physically touching specific anatomic points on the animal, and placing a novel object in the home tank. Quantitative methods used to produce noxious stimuli were the
acetic acid test and von Frey aesthesiometers. Animals that were treated with
analgesics did not demonstrate a significant difference compared with controls during behavioral assessment at 1, 6, 12, 25, 30, and 48 h after
analgesia administration. The
acetic acid test revealed a reproducible, concentration-dependent
pain response. However, a significant difference in the AAT response was not observed between control and treated groups with the tested
analgesics and doses.