Comparison of the effect of propofol and that of pentobarbital on behavioral responses to somatic and visceral stimuli in rats

: The behavioral responses to tail-flick and colorectal distension after intraperitoneal administration of either small or large dose of propofol as well as of pentobarbital were studied in rats. Immediately after baseline testing, animals were randomly divided into four groups; propofol groups of 50 mg.kg-1 (n = 4) or 100 mg.kg-1 (n = 4) and pentobarbital groups of 10 mg.kg-1 (n = 4) or 20 mg.kg-1 (n = 4). Both tests were repeated every 10 minutes for 1 hour in each group. There were no changes in the thresholds of colorectal distension and tail-flick latencies in those animals receiving small doses of propofol and pentobarbital. The thresholds for colorectal distension following administration of large doses of propofol and pentobarbital had greatly increased at 10 minutes and this increase persisted for about 30 minutes although it declined gradually. In contrast, the state of high sensitivity to tail-flick test was seen in the large dose groups of both drugs. It is concluded that there are no pharmacological differences between propofol and pentobarbital in behavioral responses to somatic and visceral stimuli in rats.