Evaluating pain behaviours: Widely used mechanical and thermal methods in rodents

• Published in: Behavioural brain research 2023-05, Vol.446, p.114417-114417, Article 114417
• Main Authors: Modi, Akshat D., Parekh, Anavi, Pancholi, Yajan N.
• Format: Article
• Language: English
• Subjects: Allodynia; Animals; Chronic Pain; Disease Models, Animal; Hot Temperature; Humans; Hyperalgesia; Hyperalgesia - drug therapy; Nociception; Pain assessment; Pain Measurement; Pain Threshold; Rats; Rats, Sprague-Dawley; Rodent; Rodentia; Sensitivity
• ISSN: 0166-4328; 1872-7549
• DOI: 10.1016/j.bbr.2023.114417

Globally, over 300 million surgical procedures are performed annually, with pain being one of the most common post-operative side effects. During the onset of injury, acute pain plays a protective role in alerting the individual to remove noxious stimuli, while long-lasting chronic pain without any physiological reason is detrimental to the recovery process. Hence, it created an urgent need to better understand the pain mechanism and explore therapeutic targets. Despite the hardship in performing human pain studies due to ethical considerations, clinically relevant rodent pain models provide an excellent opportunity to perform pain studies. Several neurobehavioural tests are used to assess the drug efficacy in rodents to determine avoidance behaviour latency and threshold. This review article provides a methodological overview of mechanical (i.e. von Frey, Mechanical Conflict System) and thermal (i.e. Hargreaves Assay, Hot and Cold Plate, Temperature Place Preference) tests to assess pain in clinically relevant pain rodent models. We further discussed the current modifications of those tests along with their use in literature, the impact of confounding variables, advantages and disadvantages. •Avoidance behaviour threshold and latency are key to evaluating rodent pain models.•Only the von Frey and thermal preference tests can measure cancer pain.•Animal’s biological age, sex, environment, and repeated testing alter pain outcome.•Combination of several mechanical and thermal tests would provide accurate outcomes.•Effective analgesics maintain the distinction between innocuous and noxious stimuli.