Dunbar, M. L., David, E. M., Aline, M. R. et al. 2014. Validation of a novel behavioral ethogram for identification of postoperative pain in the guinea pig (Cavia porcellus). American Association for Laboratory Animal Science [AALAS] Meeting Official Program, 538 (Abstract #PS48).
Although the guinea pig (Cavia porcellus) has been used in research for over a century and remains one of the most prevalent AWA covered species today, very little has been elucidated in the literature about recognition of clinical pain or analgesic efficacy in this species. Difficulty in recognizing pain in guinea pigs is primarily attributed to their innate "freeze" behavior in the presence of an observer. Classically, methods of evaluating pain in the guinea pig focus on measures of nociception (hyperalgesia and allodynia), but these lack practicality for clinical evaluation of spontaneous pain. We sought to assess pain in the guinea pig using a newer, potentially more clinically relevant, method that has been validated in other rodent species, the behavioral ethogram. In this study, 10 male guinea pigs were acclimated to novel behavioral observation cages where they were assessed by electronic von Frey measurements and their behavior recorded by remote video across 3 conditions (baseline, anesthesia only, and castration surgery) and at 3 different time points (2, 8, and 24 h post condition). The anesthesia-only condition served to control for the nonpainful, but potentially distressing components of the surgical experience. We hypothesized that at all 3 postsurgery time points there would be an increase in pain-associated behaviors via ethogram, corresponding to a decrease in nociceptive threshold measured by von Frey. When comparing postsurgery to post anesthesia-only conditions, behaviors associated with pain were significantly increased while nociceptive thresholds were significantly decreased at the 2- and 8-h time points. By 24 h, neither pain-associated behaviors nor nociceptive thresholds differed between the 2 conditions. By correlating ethogram scores with measures of nociception using electronic von Frey, we were able to validate behaviors as pain specific in the guinea pig. Thus, our novel ethogram may be used as a potential postsurgical pain assessment tool and serve as a platform for direct clinical application and future analgesia studies in this species.