DEVELOPMENT OF A CLIMBING TEST IN MICE: A NOVEL APPROACH FOR ASSESSING PAIN-LIKE BEHAVIOUR

Introduction: Postoperative pain assessment in laboratory animals is crucial for securing their welfare, improving analgesic strategies, and<br/>developing novel compounds for pain treatment. This requires improved assessment techniques. This characterisation and validation study compared the<br/>von Frey test, a widely used assay for evaluating mechanical sensitivity, with a novel climbing test. The plantar incision model of postoperative pain was<br/>used to evaluate if a pain-related injury impairs climbing behaviour. For validation, the analgesic meloxicam was administered to revert surgery-induced<br/>behavioural changes.<br/>Materials and Methods: Ninety-six C57BL/6JRj mice (48 males, 48 females) were used. Climbing and von Frey tests were conducted before and after<br/>surgery. Climbing behaviour was quantified using EthoVision®. In the validation experiment, meloxicam (10 mg/kg) was administered subcutaneously<br/>every 12 hours.<br/>Results: The von Frey test demonstrated significant surgery-induced mechanical allodynia in both sexes, with no significant effect of meloxicam. The<br/>climbing test revealed reductions in distance travelled and the frequency of climbing in the top of the cylinder post-injury. Meloxicam-treated males<br/>significantly improved their climbing behaviour, while the effect in females was not significant.<br/>Conclusion: We successfully demonstrated the climbing test as a viable tool for holistic and objective assessment of pain-related behaviours. Interestingly,<br/>it detected a significant effect of analgesia in males’ climbing behaviour that was not found in the von Frey test. The reduced efficacy of meloxicam in<br/>females highlights potential gaps in sex-specific drug development and preclinical research. Further studies on analgesic sex differences and climbing<br/>behaviour of diverse pain models are warranted.