Experimental Study On The Analgesic Effect And Mechanism Of Propofol

Objective: The experiment was performed to study the analgesic effect of propofol and its action sites.Methods: 1 . After administrations of different doses of propofol intraperitoneally, tail stimulation-vocalization tests were performed to assay its analgesic effects. Wistar Rats were randomly divided into three groups: normal saline (NS) group, propofol Img/kg group and 2mg/kg group. Basal squeak threshold and thresholds of 5 10 20 40 60 and 80 minutes were measured after i.p propofol, and then were written down. 2, To observe the analgesic action sites of propofol. Rats were randomly divided into six groups this time: intracerebroventricular antagonization group (i.c.v) subarachnoid space(intrathecal) antagonization group (i.t) both i.c.v and i.t antagonization group and three placebo-control groups. Three to five days before experiment, the rats were implanted cerebroventricular cannulae or/and inserted polyethylene catheters (PE-10). At the time of experiment ,0.15 u g bicuculline was pretreated intrathecally or intracerebroventricularly, 0.075 u g bicuculline was pretreated at the same time in the unified group, 10 minutes later, Img/kg of propofol was injected to the rat, then, the variations of squeak thresholds were measured and written down after 5 10 20 40 60 and 80 minutes. The placebo-control groups were pretreated bicuculline also ,but 10 minutes later , same volume of NS were injected i.p, squeak thresholds were measured and written down.Results: 1 The rat's squeak threshold values were greatly increased when Img/kg or 2mg/kg propofol was injected intraperitoneally. 2 Bothpretreatment with intrathecal bicuculline or/and intracerebroventricular bicuculline can significantly antagonize the analgesic effect produced by 1 mg/kg of propofol intraperitoneally . The percentage of increased squeak threshold rose up to sixty percent after i.p propofol five minutes. When the time went up, the percentage raised too. Eighty minutes later the percentage was about two hundred percent. There were no apparent differences between the three antagonization groups.Conclusion: Propofol has some analgesic effect, and its effect is mainly mediated by central y -Aminobutyric AcidA receptor(spinally and supraspinlly).The effect can be reversed by bicuculline-an GABAA receptor antagonist.