蝇蕈醇和荷苞牡丹碱对大鼠吸入异氟醚时脑环腺苷酸含量变化的影响

Effect of muscimol and bicuculline on brain cAMP content in rats undergoing isoflnrane anesthesia

目的 观察 GABAA受体激动剂蝇蕈醇和GABAA受体拮抗剂荷苞牡丹碱对大鼠吸入异氟醚时脑cAMP含量变化的影响。方法SD大鼠48只,随机分为对照组,异氟醚组,蝇蕈醇+异氟醚组,荷苞牡丹碱+异氟醚组,蝇蕈醇组和荷苞牡丹碱组。采用cAMP竞争蛋白结合分析法测定大鼠不同脑区cAMP含量。结果 与异氟醚组比较,蝇蕈醇+异氟醚组的翻正反射消失时间明显缩短(P<0.05),而荷苞牡丹碱+异氟醚组却明显延长(P<0.01)。异氟醚组的大脑皮层、脑干的cAMP含量较对照组明显升高(P<0.01)。蝇蕈醇+异氟醚组的大脑皮层、脑干的cAMP含量分别较对照组和异氟醚组升高131％、34％和83％、22％(P<0.05或0.01)。荷苞牡丹碱+异氟醚组的大脑皮层、脑干cAMP含量明显高于对照组,分别较对照组升高41％和60％(P<0.01),其两脑区的cAMP含量与异氟醚组比较却无明显不同。结论 大鼠吸入异氟醚的中枢抑制作用至少部分与GABA能神经元有关。

Objective To investigate the effects of GABAA receptor agonist-muscimol and GABAA receptor antagonist-bicuculline on brain cyclic adenosine monophosphate (cAMP) content in rats undergoing isoflurane anesthesia. Methods Forty-eight SD rats of both-sexes weighing 200-250g were randomly divided into 6 groups: group I received intraperitoneal (ip) normal saline (NS) 10ml.kg-1 (control group); group II in which animals inhaled 1.4% isoflurane for 30 min, 30 min after NS ip (isoflurane group);group IE in which animals inhaled 1.4% isoflurane for 30 min, 30 min after muscimol Img-kg ip (muscimol + isoflurane group); group IV in which animals inhaled 1.4% isoflurane for 30min, 30 min right after bicuculline 8 mg.kg-1 ip (bicuculline + isoflurane group); group V received muscimol lmg. kg-1 (muscimol group); group VI received bicuculline 8mg.kg (bicuculline group). The animals were decapitated 1h after 30min isoflurane inhalation or intraperitoneal NS or muscimol or 5min after bicuculline ip (rats developed convulsion within 7 min after bicuculline ip) . Brain was removed immediately for determination of cAMP content of cortex or brain stem. Loss of righting reflex was taken as sign of anesthesia. Brain cAMP content was measured by competitive protein binding assay. Results Muscimol shortened the time of loss of righting reflex induced by isoflurane (P < 0.05), while bicuculline prolonged the time (P<0.01) . 1.4% isoflurane inhalation significantly increased the cAMP content of cerebral cortex and brain stem and the effect was enhanced by muscimol. The cAMP content of cerebrocortex and brain stem increased by 131%, 34% and 83%, 22% in muscimol + isoflurane group as compared with that in control group and isoflurane group (P<0.01 or 0.05). The cerebrocortex and brain stem cAMP content significantly increased by 41% and 60% in bicuculline + isoflurane group as compared with that in control group (P<0.01) . There was no significant difference in the brain cAMP content betweenbicuculline + isoflurane group and isoflurane group. Conclusion 'I he depression of central nervous system by isoflurane may be medialed at least in part by GABA neurons in rats.