Applications of Rat Grimace Scale Method in Postoperative Pain Management in Rats

Alexandra Iulia DREANCA, Lucia BEL, Bogdan SEVASTRE, Ioan MARCUS


Introduction: Nowadays, 3R (replacement, reduction, refinement) concept lies in the core of laboratory animals science, one of the most important refinement strategies being the pain control. Rat Grimace Scale (RGS) is an actual and effective method used to assess pain in laboratory animals.

Aims: The purpose of this study was to find the most effective post surgery analgesic protocol, by grading the changes in the animal’s facial expression.

Materials and methods: In the present study we used 5 Wistar rats, as a pain model, ovariectomy was performed on 4 of the rats. Tramadol was administrated subcutaneously as it follows: 1 rat in pre-surgery dose of 25 mg/kg, 2 rats in post-surgery a dose of 25 mg/kg and respectively 50 mg/kg. The evaluation of pain was done across at the time 0, 2, 4 and 6 hours post-surgery using the scores of 0, 1 and 2, 0 representing the absence of pain, 1 a moderate level of pain and 2 a high level of pain.

Results: The results of the study revealed that the spayed rat without Tramadol presented the highest level of pain (1.25 - 1.75). The pre-surgery analgesia enhanced the narcosis effect, but analgesia had a short term effect, with a moderate to high level of pain (1 - 1.5). To the animal treated with a dose of 25 mg/kg post-surgery, a moderate pain level was observed (0.5 - 1.25) and to the animal with the highest dose an optimal analgesia was determined (0.25).

Conclusion: The expected analgesic effect was put forward by the 50 mg/kg dose of Tramadol and the RGS method was found to be suitable for the assessment of animal suffering in surgical experimental procedures.


refinement, pain control, pain facial recognition

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