Study Of The Antinociceptive Effect Of Propofol On Visceral Pain And Its Mechanism In Rats

Part I Antinociceptive Effect of Propofol on Chemical Visceral Pain in Rats. Objective To investigate the effect and duration of subhypnotic propofol on chemical visceral pain in rats. Methods Chemical visceral pain model created by intraperitoneal injection (ip) of 2% acetic-acid (3ml/kg) was established in male SD rats weighing 180-240g (n=50). Rats were randomly divided into emulsion (1 ml/kg) control group (group C, n=10), propofol 5mg/kg group (group P5, n=10), propofol 10mg/kg group (group P10, n=10), propofol 20mg/kg group (group P20, n=10) and thiopental sodium 5mg/kg group (group T5, n=10). All drugs were administered intraperitoneally 1 min after acetic-acid ip. The animals were then placed into an individual observation chamber to measure the writhing response. The numbers of writhes were counted in every 5 min in a duration of 30 min. Results All rats had writhing response after acetic-acid ip. The number of writhe was 24.1 5.7 in group C. Propofol at doses of 10mg/kg and 20mg/kg significantly (p<0.05 and p<0.01) reduced the number of writhe with average numbers of 16.7 2.9 and 10.8+4.6, respectively. Propofol at dose of 5mg/kg had no antinociceptive effect compared to that of emulsion. There were significant differences in the number of writhes among the groups of different doses of propofol. The mean writhing number in group T5 was 31.6 5.0, which was significantly (p<0.01) higher than that in group C. Conclusions These results suggest that propofol at subhypnotic doses have an antinociceptive effect on chemical visceral pain induced by aceptic-acid ip. The antinociception of propofol was dose-dependent. Thiopental sodium at equivalent dose of propofol 10mg/kg has no antinociceptive effect, but a hyperalgesic effect.