Effect of propofol on perception of pain in mice: study on the mechanism of action

ABSTRACT

Propofol is an intravenous anesthetic used clinically. The latencies of pain threshold of different subhypnotic doses [12.5, 25 and 50 mg kg-1] of propofol administrated intraperitoneally [ip] into mice were measured by using hot plate method technique. The possible mechanism of pain control by propofol was also investigated through blocking beta- endorphin receptors and measuring serum level of beta-endorphin. Morphine [1.5 mg kg-1, ip] was used as reference of reduction of pain sensation. The results showed that propofol in doses of 25 and 50 mg kg-1 increased significantly the latency of pain threshold, but the lower dose [12.5 mg kg-1] failed to produce any significant change. This indicated that propofol reduced pain sensation and this effect is dose-dependent. It was also observed that propofol prevents hyperalgesia produced by prostaglandin [PGE2] [0.5 mg kg-1, ip]. For investigating the mechanism of action of propofol, pretreatment with naloxone [1.0 mg kg-1, ip] abolished significantly the antinociceptive action of propofol. Furthermore, serum level of beta- endorphin was increased significantly after propofol injection particularly at the peak time of propofol action. Serum level of corticosterone was also increased significantly at the time of beta- endorphin release