Correlation between Post-Laparotomy Weight Loss and Pain in BALB/c and C57BL/6 Mice

Post-Laparotomy Weight Loss and Pain in BALB/c and C57BL/6 Mice

Abstract

        The use of animal models in surgical research can induce significant pain, particularly in mammals, which respond to pain similarly to humans. Pain affects behavior, appetite, and weight loss after surgery. This study aimed to compare the effects of pain on pre- and post-operative weight in two strains of laboratory mice, BALB/c and C57BL/6, which received morphine for post-operative pain relief. The study also aimed to compare the level of pain expression through facial indicators (Facial Mouse Grimace Scale; fMGS) at various post-operative time points, relative to pre-operative conditions. The facial expressions of the mice were scored to assess changes corresponding to pain levels, and the correlation between weight loss and post-operative pain was evaluated. The results showed a 5% weight loss during the first 3–4 days post-surgery, followed by gradual weight gain thereafter. The findings indicated that while morphine alleviated pain, it did not provide complete relief. Furthermore, there was a correlation between pain and weight loss, with a coefficient of determination (R²) of 0.82 and p = 0.0125 for BALB/c mice, and R² of 0.97 and p = 0.0004 for C57BL/6 mice. The pain assessment using the facial mouse grimace scale revealed that pain persisted until day 5 post-surgery. Therefore, despite the administration of opioid analgesics, post-operative weight loss was observed following abdominal surgery. It is recommended that pain management should be considered for prolonged pain relief including other analgesics and anti-inflammatory drugs that act through different mechanisms to relieve pain more effectively.