Protease-activated receptor 2 antagonist potentiates analgesic effects of systemic morphine in a rat model of bone cancer pain.

Abstract

Bone cancer pain affects the quality of life of cancer patients. This study was aimed at investigating the analgesic effects of combined therapies with an antagonist of proteinase-activated receptor (PAR) 2 and morphine on pain-related behaviors in a rat model of bone cancer pain. Female Wistar rats were inoculated intramedullarily with Walker 256 cells into their tibias. The analgesic effects of intraperitoneal treatment with morphine and/or intrathecal with the PAR2 antagonist, FSLLRY-NH2, on bone cancer pain-related behaviors in rats were examined. Treatment with morphine at 3 or 10 mg/kg significantly improved limb-use and weight-bearing scores and reduced the number of spontaneous flinches in rats. Treatment with FSLLRY-NH2 at 10 mmol/L also significantly improved limb use and weight bearing scores, and reduced the number of spontaneous flinches in rats. Combination a sub-analgesic dose of FSLLRY-NH2 (0.1 mmol/L) and morphine further elevated limb-use and weight-bearing scores and reduced the number of flinches compared with the effects of morphine alone in rats. Our data indicate that the combination of morphine and FSLLRY-NH2 has potent analgesic effects on bone cancer pain and our findings may aid in design of new strategies for the treatment of bone cancer pain.