Effects of Capsaicin Application to Peripheral Nerves in a Rat Model for Human Postoperative Pain

Kim, Tae Jung; Cheong, Chong Kwon; Han, Jung Uk; Lim, Hyun Kyung; Lee, Choon Soo; Lee, Hong Sik; Cha, Young Deog; Lee, Do Hyun; Lee, Sung Keun

Abstract

BACKGROUND: The interest in management of postoperative pain has increased with the development of medicine. The mechanism of postoperative pain should be understood first. Capsaicin has been proven to be a powerful agent acting selectively on nociceptive afferent fibers. This study was focused on how the perineural treatment of capsaicin affects pain after an incision in the rat model.
METHODS
Capsaicin was applied directly to sciatic nerve branches, on the are tibial, sural, and saphenous nerves. Pain behaviors to von Frey filaments, blunt probe stimulation, resting pain, and heat were evaluated on the incised feet. The grade of wound healing was assessed according to clinical findings of the wound 3 days postoperatively.
RESULTS
Capsaicin applied directly onto nerves elevated withdrawal latency to heat during the study. There were statistically significant increases of withdrawal latencies in the capsaicin group compared with the vehicle group. Capsaicin produced agreater increase of the withdrawal threshold to von Frey than the vehicle 2 days after the incision. Resting pain scores were lower in capsaicin - treated rats than in the vehicle group for 2 days. The grade of wound healing was poor in capsaicin - treated rats.
CONCLUSIONS
The perineural application of capsaicin appears to affect the pathway of transmission of postoperative pain. Current results suggest that capsaicin has a strong analgesic effect on thermal hyperalgesia and attenuates mechanical hyperalgesia by an incision. Capsaicin sensitive nerves could be involved in wound healing.