Joint, muscle, and visceral pain: Non steroidal anti-inflammatory drugs are not effective on the referred hyperalgesia of visceral pain induced by intracolonic mustard oil in the mouse

Abstract

Visceral pain is characterized by its spontaneous pain and referred hyperalgesia. Our aim was to examine the inhibitory effects of various NSAIDs on the pain behaviors and plasma extravasation induced by intracolonic mustard oil in mice. Adult male ICR mice were injected 50mg/kg of evans blue via tail vein for subsequent determination of plasma extravasation. Control group animals were given subcutaneous saline and experimental groups were given one of the following drugs: 1,3,10mg/kg of morphine; 10, 100mg/kg of ketoprofen; 5, 50mg/kg of tarasyn; 2, 20mg/kg of DFU (cyclooxygenase-2 inhibitor).Visceral pain related behaviors were counted for 20 min after intracolonic administration of 50 ulof 1.5% mustard oil. in order to test referred hyperalgesia, before intracolonic administrtion and 20 min after, the frequency of withdrawal responses to the application of von Frey hairs to the abdomen, foot and tail was tested. The colon was removed post-mortem and evans blue content measured. Visceral pain related behaviors were significantly inhibited by 3, 10 mg/kg of morphine, 50mg/kg of tarasyn, 100mg/kg of ketoprofen and 20mg/kg of DFU (P < 0.05). Response frequencies to the application of von Frey hairs were decreased by 3, 10mg/kg of morphine (P < 0.05), but not any doses of tarasyn, ketoprofen and DFU. Evans blue content was decreased by 100mg/kg of ketoprofen and 20mg/kg DFU (P < 0.05), but not other groups. These results suggest that the analgesic effects of NSAIDs on visceral pain could be mainly mediated by peripheral mechanism, reflected by inhibition of the pain behavior and inflammation, but not referred hyperalgesia.