摘要
背景:稀土元素因其独特的理化性质,具有广泛的生物效应,并具有一定的神经毒性。研究已经发现某些稀土元素如镧、钆等对神经肌肉接头和交感神经节突触传递具有一定的影响,但钐对突触传递的影响及机制尚不明确。目的:观察氯化钐对大鼠交感神经节-颈上神经节烟碱型突触传递的影响,分析其可能作用途径。设计:以细胞为观察对象,对照实验。单位:广西医科大学药理教研室。材料:选用成年Wistar大鼠40只,雌雄不拘,体质量250～320g。氯化钐由氧化钐氯化处理后得到。氧化钐由广西医科大学刘达元教授赠送,纯度99.5%,相对分子质量348.7。氯化乙酰胆碱、氨甲酰胆碱均为美国Sigma公司产品。方法:实验于2001-09/2002-12在广西医科大学实验中心神经药理学实验室完成。①将大鼠急性放血处死后,迅速将颈上神经节连同节前神经干离体后固定在浴槽内,节前神经干置于吸引电极内供电刺激。用体积分数0.95的O2和体积分数0.05的CO2混合气饱和,pH为7.4±0.05,恒温(35±0.5)℃的克氏液持续灌流标本。用内充3mol/LKCl、尖端电阻30～60MΩ的玻璃微电极穿刺离体颈上神经节神经元进行细胞内生物电记录。单脉冲(频率0.2～0.5Hz;波宽0.5～1ms;刺激强度2～10V)刺激交感节前神经干,可在颈上神经节细胞内记录到快兴奋性突触后电位。用乙酰胆碱(0.1mmol/L)或氨甲酰胆碱(0.1mmol/L)灌流神经节30～60s可记录到颈上神经节细胞膜除极反应。②比较1×(10-7～10-4)mol/L氯化钐灌流对颈上神经节细胞快兴奋性突触后电位、膜电位、膜电阻和乙酰胆碱、氨甲酰胆碱膜除极发应的影响;在灌流高钙(10mmol/L)克氏液易化快兴奋性突触后电位后,继用含氯化钐的高钙克氏液灌流,观察氯化钐对高钙易化快兴奋性突触后电位作用的影响。实验中所用药物均用克氏液或改良克氏液配成相应浓度直接灌流神经节。③采用配对t检验比较灌流药物前后生物电差异。主要观察指标:①氯化钐对大鼠颈上神经节的快兴奋性突触后电位的影响。②对颈上神经节细胞膜电位和膜电阻的影响。③对乙酰胆碱和氨甲酰胆碱膜除极化反应的影响。④氯化钐对高钙(10mmol/L)易化快兴奋性突触后电位作用的影响。结果:①1×(10-7～10-4)mol/L的氯化钐能可逆性地抑制大鼠颈上神经节的快兴奋性突触后电位[1×10-4,1×10-5,1×10-6,1×107mol/L的氯化钐对大鼠颈上神经节细胞快兴奋性突触后电位幅度抑制百分率分别为(49.78±13.85)%(n=20),(39.05±4.05)%(n=10),(29.83±9.73)%(n=10),(16.30±2.16)%(n=10),P<0.05～0.01]。1×10-4mol/L的氯化钐可使顺行动作电位变成快兴奋性突触后电位(n=5)。②1×10-4mol/L的氯化钐灌流对乙酰胆碱(n=5)和氨甲酰胆碱(n=7)膜除极化反应无明显影响(P>0.05)。③1×(10-7～10-4)mol/L对颈上神经节细胞膜电位、膜电阻无明显影响(n=67,P>0.05)。④1×10-4mol/L氯化钐能拮抗高钙(10mmol/L)对快兴奋性突触后电位的易化作用(n=5,P<0.01)。结论:氯化钐通过突触前机制抑制大鼠交感神经节颈上神经节烟碱传递,可能与抑制突触前钙离子内流有关。
BACKGROUND： The rare earth elements （REs） have multiple bio-activities and some extent neurotoxicity, Because of their distinct physical and chemical properties.The studies on neuromuscular junction and sympathetic ganglia have shown that some REs, such as lanthanum（La）, gadolinium （Gd）,etc, exert considerable effects on synaptic transmission, but the effects and mechanism of Samarium on synaptic transmission are still unknown.
OBJECTIVE： To investigate the effects and impossible mechanism of Samarium Chloride （SmCl3） on the nicotinic transmission in the isolated sympathetic ganglia, superior cervical ganglion （SCG） of rats.
DESIGN： Controlled experimental study based on cells.
SETTING： Department of Pharmacology, Guangxi Medical University.
MATERIALS： Totally 40 adult Wistar rats （weighing 250-300 g） of either sex, provided by the Experimental Animal Center of Guangxi Medical University, were used in this study. SmCl3 was made by the chlorination of Samarium Oxide with purity 99.5% and relative molecule mass 348.7, presented by Professor Liu Da-yuan, Guangxi Medical University. Acetylcholine chloride （ACh） and carbachol （Carb） were purchased from Sigma.
METHODS： The experiment was completed at the neuropharmacology lab of the experimental center of Guangxi Medical University from September 2001 to December 2002. After sacrificing animals by acute exsanguination, SCG together with their preganglionic nerve trunks were isolated rapidly, then transferred to the recording chamber, the preganglionic nerve trunk was drawn into a suction electrode for orthodromic stimulation. The ganglia were snperfused continuously with a Krebs solution, saturated with 950 mL/L O2 and 5mL/L CO2, pH 7.4±0.05, （34±0.5） ℃.The fiber containing glass microelectrodes filled with 3 mol/L KCI （30-60 MΩ tip resistance） were used to impaled cells and do intracellular recording. The fast excitatory postsynaptic potentials （FEPSPs） were evoked in SCG neurons by single pulse stimulations （0.2-0.5 Hz, 0.5-1.0 ms, 2-10 V） on preganglionic nerve trunk. The remarkable membrane depolarization would be recorded in SCG neurons by superfusing ganglia with exogenous ACh （0.1 mmol/L） or Carb（0.1 mmol/L） for 30-60 s. The effects of 1×（10^-7-10^-4） mol/L SmCl3 on FEPSPs, membrane potentials, membrane resistance, exogenous ACh and Carb-induced membrane depolarization of SCG neurons were investigated in this experiment.The effects of SmCl3 on the facilitation of high Ca^2＋ （10 mmol/L ） on FEPSPs were also be observed, namely, first superfusing the ganglia with high Ca^2＋ （10 mmol/L） to facilitate FEPSPs, then superfusing the ganglia with Ca^2＋（10 mmol/L） contained Sml3. All the drugs were solved in Krebs solution or improved Krebs solution and applied to ganglia by superfusion in known concentration.The bioeleetricity difference before and after the drug superfusion were analyzed by paired Student＇s t test.
MAIN OUTCOME MESURES： ①Effects of SmCl3 on FEPSPs.②Effects of SmCl3 on membrane potentials and membrane resistances. ③Effects of SmCl3 on. exogenous ACh and Carb-induced membrane depolarization. ④Effects of SmCl3 on the facilitation of high Ca^2＋ （10 mmol/L ） on FEPSPs. RESULTS： ①1×（10^-7-10^-4）mol/L SmCl3 could reversibly depressed the FEPSPs of rats SCG neurons [the amplitude inhibitory percentage of FEPSPs of 1×10^-4, 1×10^-5, 1×10^-6, 1×10^7 mol/L SmCl3 was （49.78±13.85）% （n=20）,（39.05±4.05）%（n=10）,（29.83±9.73）%（n=10）and （16.30±2.16）%（n=10）respectively （P 〈 0.05-0.01）].1×10^-4 mol/L SmCl3 could chang APs into FEPSPs （n=5）.②The membrane depolarization induced by ACh （n=5） and Carb （n=7） were not significantly changed by 1×10^-4 mol/L SmCl3（P 〉 0.05）.③The membrane potential and membrane resistance were not significantly altered by 1×（10^-710^-4）mol/L SmCl3（n=67）, P 〉 0.05. ④1×10^-4 mol/L SmCl3 could antagonized the facilitation of high Ca^2＋ （10 mmol/L ） on FEPSPs （n=5）, P 〈 0.01.
CONCLUSION： SmCl3 can depresses nicotinic transmission in rats sympathetic ganglia by presynaptic mechanisms, perhaps due to its inhibition on Ca^2＋ influx.
出处
《中国临床康复》
CSCD
北大核心
2006年第18期190-192,共3页
Chinese Journal of Clinical Rehabilitation
基金
广西科技厅自然科学基金资助项目(桂科自9811005)
广西教育厅科研资助项目(桂教科研2002316)~~
