Preemptive analgesia is used for postoperative pain management, providing pain relief with few adverse effects. In this study, the effect of a preemptive regime on rat behavior and c-fos expression in the spinal cord of the uterine surgical pain model was evaluated.
Method: It was a lab-based experimental study in which sixty female Sprague-Dawley rats; eight to ten weeks old, weighing 150-300 gm were used. The rats were divided into three main groups: i) Control group (CG), ii) superficial pain group (SG) (with skin incision only), iii) deep pain group (with skin and uterine incisions). Each group was further divided into three subgroups based on the type of preemptive analgesia administered i.e., "tramadol, buprenorphine, and saline subgroups." Pain behavior was evaluated using the "Rat Grimace Scale" (RGS) at 2, 4, 6, 9 and 24 hours post-surgery. Additionally, c-fos immunohistochemistry was performed on sections from the spinal dorsal horn (T12-L2), and its expression was evaluated using optical density and mean cell count two hours postoperatively.
Results: Significant reduction in the RGS was noted in both the superficial and deep pain groups within the tramadol and buprenorphine subgroups when compared to the saline subgroup (p≤0.05). There was a significant decrease in c-fos expression both in terms of number of c-fos positive cells and the optical density across the superficial laminae and lamina X of the spinal dorsal horn in both SD and DG (p≤0.05). In contrast, the saline group exhibited c-fos expression primarily in laminae I-II and III-IV for both superficial and deep pain groups and lamina X in the deep pain group only (p≤0.05).
Conclusion: A preemptive regimen results in significant suppression of both superficial and deep components of pain transmission. These findings provide compelling evidence of the analgesic efficacy of preemptive treatment in alleviating pain response associated with uterine surgery.
Keywords: Rat Grimace Scale; buprenorphine; c-fos expression; preemptive regimen; surgical pain model; tramadol.