依托咪酯对大鼠海马脑片突触长时程增强的影响

Effect of etomidate on synaptic long-term potentiation in rat hippocampal slices

目的 评价依托咪酯对大鼠海马脑片突触长时程增强（LTP）的影响。方法 雄性SD大鼠，断头后取出海马组织，制备厚400μm的海马脑片。采用细胞外微电极记录技术，记录海马脑片CA1区细胞外群体峰电位（PS）。取42张脑片，随机分为6组（n=7）：用正常的人工脑脊液（ACSF）灌流海马脑片记录正常的PS，待其稳定后，对照组继续灌流ACSF，不同浓度依托咪酯组分别用含依托咪酯1μmol／L（依托咪酯1μmol／L组）、2μmol／L（依托咪酯2μmol／L组）、5μmol／L（依托咪酯5μmol／L组）、10μmol／L（依托咪酯10μmol／L组）、20μmol／L（依托咪酯20μmol／L组）的ACSF灌流，记录PS幅值。另取84张脑片，随机分为12组（n=7）：用正常ACSF灌流海马脑片，记录稳定正常的PS 30min，LTP组继续灌流ACSF，其余各组分别用含依托咪酯1μmol／L（LTP-依托咪酯1μmol／L组）、2μmol／L（LTP-依托咪酯2μmol／L组）、5μmol／L（LTP-依托咪酯5μmol／L组）、10μmol／L（LTP-依托咪酯10／μmol／L组）、20μmol／L（LTP-依托咪酯20μmol／L组）、印防己毒素50μmol／L（印防己毒素组）、荷包牡丹碱10μmol／L（荷包牡丹碱组）、CGP35348 5μmol／L（CGP35348组）、印防己毒素50μmol／L＋依托咪酯10μmol／L（印防己毒素＋依托咪酯组）、荷包牡丹碱10μmol／L＋依托咪酯10μmol／L（荷包牡丹碱＋依托咪酯组）、CGP353485μmol／L＋依托咪酯10μmol／L（CGP35348＋依托咪酯组）的ASCF灌流，记录PS30min后，施以100Hz的高频刺激（HFS），记录PS幅值。结果 与LTP组比较，LTP-依托咪酯2μmol／L组、LTP-依托咪酯5μmol／L组、LTP-依托咪酯10μmol／L组、LTP-依托咪酯20μmol／L组和CGP35348＋依托咪酯组HFS后PS幅值降低（P〈0．05或0．01），印防己毒素组、荷包牡丹碱组、CGP35348组HFS后PS幅值差异无统计学意义（P〉0．05）；与依托咪酯LTP10μmol／L组比较，印防己毒素＋依托咪酯组和荷包牡丹碱＋依托咪酯组HFS后PS幅值增加（P〈0．01）。结论 依托咪酯可通过激活大鼠海马GABA。受体抑制LTP的形成，从而影响学习和记忆功能。

[ Abstract] Objective To investigate the effect of etomidate on the synaptic long-term potentiation （LTP） in the CA1 region of rat hippocampal slices and the underlying mechanism. Methods Adult male SD rats aged 2 months weighing 200-250 g were anesthetized with ether and decapitated. Their brains were immediately removed and hippocampal slices （400 μm thick） were prepared. The slices were incubated in artificial cerebrospinal fluid （ACSF） at room temperature for at least 120 rain before use. The experiment was performed in 2 parts. Part Ⅰ forty-two slices were randomly divided into 6 groups （ n = 7 each） ： in group Ⅰ the slices were perfused with plain ACSF （control group） and in group Ⅱ ,Ⅲ, Ⅳ, V and Ⅵ the slices were perfused with ACSF containing etomidate 1, 2, 5, 10 and 20 μmol/L respectively to determine the effect of different concentrations of etomidate on the amplitude of evoked population spikes （PSs）. Part Ⅱ ： another 84 slices were randomly divided into 12 groups （n = 7 each）： the slices were perfused with plain ACSF in group Ⅰ （control group）; with ACSF containing etomidate 1, 2, 5, 10 and 20μmol/L respectively in group Ⅱ -Ⅵ ; with ACSF containing plcrotoxin 50μmol/L in group Ⅶ, or bicuculline 10μmol/L in group Ⅶ or CGP35348 5 μmol/L in group IX or picrotoxin 50 μmol/L ＋ etomidate 10μmol/L （group Ⅹ ） or bicuculline 10 μmol/L ＋ etomldate 10 μmol/L （group Ⅺ ） or CGP35348 5 μmol/L ＋ etomidate 10μmol/L （ group Ⅻ ）. Thirty minutes after PSs were recorded, high frequency stimulation （HFS） at 100 Hz was applied for 15 rain to induce LTP. If the amplitude increased by 〉 30% of the baseline value and maintained for more than 30 min, the induction of LTP was considered successful. Results In part etomidate 5, 10 and 20 μmol/L significantly decreased PS amplitude in group Ⅳ , Ⅴ and Ⅵ as compared with control group （ Ⅰ ）. In part ⅡPS amplitude was significantly increased by （52 ± 12） % after HFS as compared with the baseline value before HFS in control group （ Ⅰ ）. The amplitude of PS after HFS was significantly decreased after HFS in group LTP m , Ⅳ , Ⅴ and Ⅵ （etomidate 2, 5, 10, 20 μmol/L） as compared with group LTPⅠ （ control group）. The amplitude of PS was significantly increased after HFS as compared the baseline before HFS in picrotoxin, bicuculline and CGP35348 （Ⅵ ,Ⅷ , Ⅸ ） groups. The PS amplitude was significantly increased after HFS in picrotoxin ＋ etomidate grop and bicucullin ＋ etomidate group as compared with the baseline before HFS and LTP etomidate 10 μmol/L group. Conclusion Etomidate can inhibit LTP by activating GABAA receptor in hippocampus, thus affecting learning and memory function.