ABSTRACT
Objective To examine the effects of different doses of midazelam on ED50 of emulsified isoflurane and to determine the type of interaction between them for hypnosis by isobelographic analysis in rats. Methods One hundred and twenty-five adult male SD rats weighing 240-300 g were randomized into 5 groups (n=25 each): group Ⅰmidazolam (M); group Ⅱ emulsified isnflurane (Ⅰ); group Ⅲ ,Ⅳ ,Ⅴ, 1/4, 1/2 and 3/4 ED50 of midazelam for hypnosis + emulsified isoflurane (MI1 , MI2, MI3). Up-and-down sequential experiment was used to determine ED50of midazolam and emulsified isoflurane for loss of righting reflex in group Ⅰ -Ⅴ . The intial dose of midazolm was 17.3 mg/kg in group M. The initial doses of emulsified isoflurane (120 mg/ml) were 0.55 (in group Ⅰ, 0.22 (MI1), 0.19 (MI2) and 0.12 ml/kg (MI3) respectively. In group MI1-3 midazolam was injected over 15 seconds and after an interval of 2.5 min emulsified isoflurane was injected over 10 s. ED50 was calculated using Dixon-Mood method. Isebolographic and algebraic analyses were used to determine the type of interaction between midazolam and emulsified isoflurane. Results The five groups were comparable with respect to M/F sex ratio and body weight. The Edso of midazolam was 26.0 mg/kg in group M. Midazolam 6.5, 13.0 and 19.5 mg/kg were given in group MI1 , MI2 and MI3 respectively. The ED50 of emulsified isoflurane was 0.67 (ingroup Ⅰ), 0.30 (MI1), 0.22 (MI2) and 0.18 ml/kg (MI3) respectively. The isobolographic analysis indicated that with increasing doses of midazolam, the Edw of emulsified isoflurane decreased progressively in a non-linear fashion. The isobolographic and algebraic analyses demonstrated that the interaction between midazolam and emulsified isoflurane was synergistic for hypnosis. Conclusion The hypnosis is synergistic when midazolam 6.5,13 mg/kg are combined with emulsified isoflurane and additive when midazolam 19.5 mg/kg is combined with emulsified isoflurane.
ABSTRACT
OBJECTIVE:To investigate whether the magnesium sulfate injection(MSI)into cisterna magna in a rabbit with subarachnoid hemorrhage(SAH)can reverse the cerebral vasospasm and damage of brain tissues.METHODS:The single-hemorrhage SAH rabbit model was used.Thirty New Zealand white rabbits were randomly divided into the following three groups(n=10,in the each group):sham group,model group and MSI group.At 24 hours after SAH,the rabbits were injected with 0.1 mL?kg-1 of saline into cisterna magna in sham and model groups,while 0.1 mL?kg-1 of 4% magnesium sulfate was injected into cisterna magna of rabbits in MSI group.All animals were sacrificed at 48 hours after SAH.Basilar arteries and hippocampus were then removed for measurement of the cross-sectional areas of basilar arteries and the hippocampus normal neuron density of CA1 regions.RESULTS:The cross-sectional areas of basilar artery and the hippocampus normal neuron density of CA1 regions were smaller in model group than in the other two groups(P0.05).CONCLUSIONS:This study results indicate that injecting magnesium sulfate into cisterna magna can reverse the cerebral vasospasm and the following hippocampal neuron damage in rabbits with subarachnoid hemorrhage.