脑摄取平衡时丙泊酚对犬脑不同区域GAT-1 mRNA和GAD65 mRNA的影响

摘要

目的 探讨不同剂量丙泊酚恒速静注50 min时对犬脑不同区域γ-氨基丁酸浆膜转运体1(GAT-1)及谷氨酸脱羧酶65(GAD65)mRNA的影响.方法 18只12～18月健康杂种犬,雌雄不限,体质量10～12 kg,随机分为对照组(C组)、低剂量组(L组)和高剂量组(H组),每组6只.L组和H组分别以丙泊酚5.5 mg/kg和7.0 mg/kg静脉注射,续以55 mg/(kg.h)和70 mg/(kg.h)恒速静脉输注50 min,分别取颈内动、静脉血各2ml后,快速静脉注射10％ KC1注射液2mg/kg处死；采用高效液相色谱-紫外法(HPLC-UV)测动、静脉血浆丙泊酚浓度.C组不给予任何干预措施,快速静脉注射10％ KC1注射液2 mg/kg处死.3组均解剖获取下丘脑、底丘脑、背侧丘脑、海马、脑桥、顶叶、额叶组织,采用实时荧光定量PCR技术测脑组织中GAT-1 mRNA和GAD65mRNA的表达水平.结果 丙泊酚静脉输注50 min时,L组和H组丙泊酚血浆浓度(动脉-动脉,静脉-静脉比较)差异显著(P＜0.01),而两组颈内动脉和静脉丙泊酚血浆浓度比较差异均无统计学意义(P＞0.05).L组和H组下丘脑和海马GAT-1 mRNA的相对表达量均明显高于C组(P＜0.05,P＜0.01),两组之间差异无统计学意义(P＞0.05)；其他脑区GAT-1 mRNA的相对表达量3组均无显著差异.下丘脑和海马GAT-1 mRNA相对表达量的变化率,L组分别为(61.26±7.17)％和(79.34±39.95)％,差异无统计学意义(P＞0.05)；H组分别为(74.64±19.63)％和(97.12±32.31)％,差异无统计学意义(P＞0.05).背侧丘脑GAD65 mRNA的相对表达量,L组和H组均明显高于C组(P＜0.01)；其他脑区GAD65 mRNA的相对表达量3组均无显著差异.结论 丙泊酚恒速静注50 min,犬脑对丙泊酚的摄取处于平衡状态,此时,丙泊酚可明显上调下丘脑和海马GAT-1 mRNA以及背侧丘脑GAD65mRNA的表达,呈非剂量依赖性.%Objective To investigate the expressions of gamma aminobutyric acid transporter 1 (GAT-1) and glutamate decarboxylase 65 (GAD65) mRNA in different brain regions at brain propofol uptake equilibrium in dogs. Methods Eighteen 12- to 18-month-old healthy hybrid dogs were randomized equally into control group (group C), low dose group (group L), and high dose group (group H), In groups L and H, anesthesia was administered by intravenous injection of 5.5 and 7.0 mg/kg propofol followed by propofol infusion at a constant rate of 55 and 70 mg·kg-1· h-1 for 50 min, respectively Blood samples were taken from the internal carotid artery and jugular vein to measure plasma propofol concentrations, and the brain tissues of the hypothalamus, sub thalamus, dorsal thalamus, hippocampus, pons, parietal lobe and frontal lobe were examined for GAT-1 and GAD65 mRNA expressions using quantitative real-time PCR. Results In groups L and H, propofol infusion at a constant rate for 50 min resulted in comparable plasma propofol concentrations between the internal carotid artery and jugular vein (P> 0.05), but the concentrations differed significantly between the two groups (P<0.01). GAT-1 mRNA levels in the hypothalamus and hippocampus were significantly higher in groups L and H than in group C (P<0.05 and P<0.01), but comparable between the former two groups. The variations of GAT-1 mRNA levels between the hypothalamus and hippocampus were similar in both group L [(61.26±7.17)% and (79.34±39.95)%, P>0.05] and group H [(74.64±19.63)% and (97.12+32.31)%, P>0.05]. GAT-1 mRNA levels in other brain regions showed no significant difference among the 3 groups. GAD65 mRNA levels were similar between group L and group H, but both significantly higher than that in group C (P<0.01). GAD65 mRNA in other brain rnregions had no significant difference among the 3 groups. Conclusions GAT-1 mRNA in the hypothalamus and hippocampus and GAD65 mRNA in the dorsal thalamus are upregulated when propofol uptake reaches an equilibrium in the brain of dogs.