豚鼠耳蜗外毛细胞的急性分离及钾离子通道的研究

本文对豚鼠耳蜗离体外毛细胞的细胞活性及底侧膜处电压依赖性钾离子通道进行了研究,结果表明：（１）离体外毛细胞悬液保存在４℃时,可延长存活时间达７ｈ以上。（２）外毛细胞的静息电位：应用电流钳方法,在刚形成全细胞方式时其细胞内静息电位为－７３．７±６．９ｍＶ,２ｍｉｎ后为－９４．８±４．１ｍＶ（ｘ±ｓ,ｎ＝１０）。（３）全细胞方式记录到的电压依赖性外向Ｋ＋电流是由快钾电流和延迟整流钾电流两部分组成,快钾电流的激活电位为－６０～－５０ｍＶ,延迟整流钾电流的激活电位为－４０～－３０ｍＶ,电流－电压关系曲线呈“Ｓ形上升”趋势。外向Ｋ＋电流被ＴＥＡ（２０ｍｍｏｌ／Ｌ）阻断后,可观察到一种电压依赖性内向电流     

新生大鼠脊髓薄片中的运动神经元对腹外侧索刺激的反应

在新生大鼠脊髓薄片细胞内记录了２５个经送行刺激鉴定的运动神经元（ＭＮ）,发现腹外侧索刺激可在８０％的ＭＮ诱发去极化反应（ＥＰＳＰ）。在静息电位水平ＥＰＳＰ的潜伏期、达峰时间、幅度、半衰时间和时程分别为１．２±０．２ｍｓ,２．６±０．４ｍｓ,１３±３ｍＶ,５．３±１．６ｍｓ和３１±８ｍｓ。ＥＰＳＰ呈等级性和膜电位依赖性,平均翻转电位为－８ｍＶ,潜伏期在０．—５Ｈｚ频率的刺激时相对恒定,但刺激频率＞２０Ｈｚ时ＥＰＳＰ变小或被取消。ＥＰＳＰ在低钙高镁溶液中被阻抑叵在无镁溶液中增强。犬尿烯酸（０．５—１ｍｍｏｌ／Ｌ）可逆地阻断ＥＰＳＰ,但氯胺酮（５０—１００μｍｏｌ／Ｌ）仅部分抑制之。结果表明腹外侧索中的下行纤维可能释放兴奋性氨基酸而激活ＭＮ。     

豚鼠球囊毛细胞的分离及钾离子流的研究

目的：研究前庭毛细胞的细胞活性及膜上钾通道的类型。方法：用酶深化后机械法分离豚鼠球囊毛细胞,并用全细胞膜片钳观察豚鼠球囊Ⅱ型毛细胞侧膜上的钾通道电流。结果：①胶原酶Ⅳ浓度为０．３５ｍｇ／ｍｌ时,分离的毛细胞数量最多,存活时间最长;②当钳制电位为－１００ｍＶ,以１０ｍＶ的步距,从－７０ｍＶ至＋２０ｍＶ阶跃,随着膜 电位的去极化,可记录到一系列快速、瞬时的以Ａ型钾通道为主的外向电流,４－Ａｐ对其有特异     

丹皮酚对心肌细胞自律性和延迟后除极的影响

目的与方法：采用常规玻璃微电极技术研究丹皮酚对离体心肌细胞自律性（ＡＭ）、延迟后除极（ＤＡＤ） 及触发活动（ＴＡ）的影响。结果：１．８×１０－４ｍｏｌ／Ｌ丹皮酚灌流组,肾上腺素（Ａｄｒ）的阈浓度空白对照组为（１．２８±０．５７）μｍｏｌ／Ｌ,药后为（１．５６±０．５３）μｍｏｌ／Ｌ（ｎ＝９,Ｐ＞０．０５）;用（１．８×１０－ ３） ｍｏｌ／Ｌ丹皮酚（Ｐａｅ）灌流组,Ａｄｒ 浓度由空白对照组的（１．２２ ±０．６２）μｍｏｌ／Ｌ升高到（６．２２±２．１１）μｍｏｌ／Ｌ（ｎ＝９,Ｐ＜０．０１）。１．８×１０－３ｍｏｌ／Ｌ的Ｐａｅ 能明显抑制哇巴因（Ｏｕａ）诱发的ＤＡＤ的幅值,当基本刺激周长为５００,４００,３００ 和２００ ｍｓ 时,其ＤＡＤ幅值从（５．５±２．０）ｍＶ,（７．３±２．１）ｍＶ,（８．０ ±２．４）ｍＶ和（９．２±１．９）ｍＶ减小到（３．０±１．１）ｍＶ、（３．６±１．７）ｍＶ,（４．３±２．０） ｍＶ和（５．９ ±１．６） ｍＶ,Ｐ＜０．０１。当基本刺激周长为２００ ｍｓ时,ＴＡ 数目由５．５±１．０ 降至０．７±０．３（Ｐ＜０．０１）。结论：丹皮酚能抑制心肌细胞ＡＭ、ＤＡＤ及ＴＡ,具有抗心律失常作用     

β-淀粉样蛋白31-35片段对海马神经元分离膜片Ca~(2 )激活大电导钾通道的抑制

为了确定β－淀粉样蛋白（ＡβＰ）在影响神经元电生理特性并导致神经毒作用时的最短活性序列，实验采用膜片钳技术，在急性分离的大鼠海马ＣＡＩ区锥体细胞的“内面向外”式膜片上，观察了ＡβＰＲ的３１－３５和２５－３５片段对Ｃａ２＋激活大电导钾（ＢＫ）通道活动的影响。结果显示，浴液中给予 ５μｍｏｌ／Ｌ的ＡβＰ ３１－３５后，ＢＫ通道的平均开放概率（Ｐｏ）和开放频率在１～３ｍｉｎ内分别减少了８５．８％（Ｐ＜０．０１）和７２．１％（Ｐ＜０．０１）；平均开放时间减少了４１．１％（Ｐ＜０．０１）；平均电流幅度则无明显改变（Ｐ＞０．０５）；给子同样摩尔浓度的ＡβＰ　２５－３５后，ＢＫ通道平均Ｐｏ减少了８５．５％（Ｐ＜０．０１），平均开放时间减少了５１．４％，（Ｐ＜０．０５）。结果提示，两种ＡβＰ片段对海马神经元ＢＫ通道具有抑制作用，这可能与ＡβＰ的神经毒性作用有关；ＡβＰ３１－３５片段可能是ＡβＰ分子中影响细胞电生理特性的最小活性序列。     

α受体激动对绵羊心肌瞬时性内向离子流的影响

用乙酰毒毛旋花子甙元（ＡＳ）０．０５μｍｏｌ／Ｌ诱发绵羊心浦肯野纤维产生稳定的瞬时性内向离子流（Ｉｔｉ）,用普萘洛尔０．５μｍｏｌ／Ｌ阻断β受体,观察α受体激动剂苯肾上腺素（ＰＥ）０．３,１．０μｍｏｌ／Ｌ对Ｉｔｉ幅值与时程的影响。ＰＥ１．０μｍｏｌ／Ｌ灌流２０,５０ｍｉｎ时Ｉｔｉ幅值分别由对照值１２．８±１．９ｎＡ减小至１０．７±１．２ｎＡ（ｎ＝５,Ｐ＜０．０５）与９．６±１．９ｎＡ（ｎ＝５,Ｐ＜０．０１）;ＩｔｉＤ５０时程分别由对照值１４５±２４．４ｍｓ延长至１８３．３±２８．１ｍｓ（ｎ＝５,Ｐ＜０．０５）与２０７．５±３４．２ｍｓ（ｎ＝５,Ｐ＜０．０１）,ＰＥ对Ｉｔｉ的抑制作用呈剂量依赖性与时间依赖性。Ｉｔｉ到达峰值的时间和回复到基线的时间都延长,提示ＰＥ作用下Ｉｔｉ通道动力学发生了变化。如果在β受体激动剂异丙肾上腺素（ＩＳＯ）１．０μｍｏｌ／Ｌ增强Ｉｔｉ的基础上,ＰＥ１．０μｍｏｌ／Ｌ灌流１０ｍｉｎ,对Ｉｔｉ幅值的抑制及时程的延长作用更显著,Ｉｔｉ幅值由对照值１５．６±３．２ｎＡ减小到１０．３±２．２ｎＡ;ＩｔｉＤ５０由９２．５±１４．３ｍｓ延长到１３２．５±３６．０ｍｓ（ｎ＝５,Ｐ＜０．０１）。     

兔血管平滑肌延迟整流钾通道研究及其与克隆Kv1.5通道的电生理特性比较

本文用膜片箝全细胞技术比较了研究了单个兔肺动脉血管平滑肌细胞上延迟整流钾通道与克隆Ｋｖ１．５通道的电生理及药理学特性。将平滑肌细胞箝制在－４０ｍＶ,以１０ｍＶ的步跨阶跃去极化（０￣６０ｍＶ）可产生一系列快速上升的外向电流,几无衰减,其激活曲线的Ｖ１／２为２７．２ｍＶ。灌流液中加入１００ｍｍｏｌ／Ｌ和ＴＥＡ １ｍｍｏｌ／Ｌ ４ＡＰ,电流幅度均明显减小,细胞外Ｃａ＾２＋水平由１．５ｍｍｏｌ／Ｌ降至０．     

豚鼠主动脉前庭自发性慢反应电位去极离子流的初步分析

为研究主动脉前庭自发慢反应电位的去极离充性质,利用豚鼠的离体以及心脏,常规玻璃微电极细胞内记录方法和离子通道组断剂,观测最大舒张电位（ＭＤＰ）、０相除极幅度（ＡＰＡ）、０相最大除极速度（Ｖｍａｘ）、４个自动除极速度（ＶＤＤ）、复极５０％（ＡＰＤ５０）和９０％（ＡＰＤ９０）的时间以及自发放电频率（ＲＰＦ）。结果发现：⑴０．５μｍｏｌ／Ｌ尼索地平（Ｎｉｓ）可使该慢电位的ＡＰＡ、Ｖｍａｘ、ＶＤＤ明显减小     

血管紧张素Ⅱ对大鼠心肌肌浆网Ca~(2+),Mg~(2+)-ATPase基因转录调节的影响

观察血管紧张素Ⅱ（ＡｎｇⅡ）对心肌肌浆网Ｃａ２＋,Ｍｇ２＋－ＡＴＰａｓｅ基因（ＳＥＲＣＡ２ａ）转录调节的影响,评价ＤＭＰ８１１对此效应的干预作用．６周龄雄性ＳＤ大鼠随机分为３组,每组６只．组１：生理盐水输注;组２：ＡｎｇⅡ输注＋ＤＭＰ８１１管饲（３ｍｇ·ｄ－１·ｋｇ－１）;组３：ＡｎｇⅡ输注（２００ｎｇ·ｍｉｎ－１·ｋｇ－１．１周后称其体重,取心脏并称重,提取心脏总ＲＮＡ后采用Ｎｏｒｔｈｅｒｎｂｌｏｔ的方法检测ＳＥＲ－ＣＡ２ａ的转录水平,采用ＲＴ－ＰＣＲ检测ＡｎｇⅡ１型受体（ＡＴ１）ｍＲＮＡ水平．实验后,组３心重（ＣＷ）、心重／体重（Ｃ／Ｂ）、ＡＴ１受体转录水平均高于组１（分别增加４．７±０．４％,４．９±０．９％和２４．７±３．５％;Ｐ＜０．０１）,而ＳＥＲＣＡ２ａ基因转录水平显著低于组１（降低２０．１±３．０％,Ｐ＜０．０１）,并且ＳＥＲＣＡ２ａｍＲＮＡ水平与ＡＴ１受体ｍＲＮＡ水平呈负相关（ｒ＝－０．７４,Ｐ＜０．０１）．ＡｎｇⅡ导致的上述改变能被ＤＭＰ８１１完全阻断．ＡｎｇⅡ通过其Ⅰ型受体的介导,诱导了ＳＥＲＣＡ２ａ的转录下调     

α受体激动对绵羊心脏浦肯野纤维延迟后除极的影响

用乙酰毒毛旋花子成元０．２μｍｏｌ／Ｌ诱发绵羊心脏浦肯野纤维产生延迟后除极（ＤＡＤ）,采用细胞内微电极记录。在用普奈洛尔１．０μｍｏｌ／Ｌ阻断β受体条件下,苯肾上腺素１．０μｍｏｌ／Ｌ使ＤＡＤ幅值由８．１±２．２ｍＶ增至９．５±２．８ｍＶ,时程由２４０±４７ｍｓ延长到２７３±４７ｍｓ（ｎ＝１３,ＰＭ＜０．０１）,ＤＡＤ上升速率由０．０３９±０．０２３Ｖ／ｓ增至０．０５１±０．０２６Ｖ／ｓ（ｎ＝１３,Ｐ＜０．０５）,ＤＡＤ在动作电位后出现的时间提前了３０±４７ｍｓ（ｎ＝１３,Ｐ＜０．０５）。用去甲肾上腺素１．０μｍｏｌ／Ｌ增强ＤＡＤ引起触发活动时,酚妥０拉明１．８μｍｏｌ／Ｌ不能抑制触发活动,普奈洛尔１．０μｍｏｌ／Ｌ能抑制之。上述结果表明α受体激动对ＤＡＤ有轻度增强作用,但由ＤＡＤ引起的触发活动,α受体阻滞剂的抑制作用不如β受体阻滞剂有效。     

Potassium current activated by depolarization of dissociated neurons from adult guinea pig hippocampus

Currents were generated by depolarizing pulses in voltage-clamped, dissociated neurons from the CA1 region of adult guinea pig hippocampus in solutions containing 1 microm tetrodotoxin. When the extracellular potassium concentration was 100 mM, the currents reversed at -8.1 +/- 1.6 mV (n = 5), close to the calculated potassium equilibrium potential of -7 mV. The currents were depressed by 30 mM tetraethylammonium in the extracellular solution but were unaffected by 4-aminopyridine at concentrations of 0.5 or 1 mM. It was concluded that the currents were depolarization-activated potassium currents. Instantaneous current-voltage curves were nonlinear but could be fitted by a Goldman-Hodgkin-Katz equation with PNa/PK = 0.04. Conductance-voltage curves could be described by a Boltzmann-type equation: the average maximum conductance was 65.2 +/- 15.7 nS (n = 9) and the potential at which gK was half-maximal was -4.8 +/- 3.9 mV (mean +/- 1 SEM, n = 10). The relationship between the null potential and the extracellular potassium concentration was nonlinear and could be fitted by a Goldman-Hodgkin-Katz equation with PNa/PK = 0.04. The rising phase of potassium currents and the decay of tail currents could be fitted with exponentials with single time constants that varied with membrane potential. Potassium currents inactivated to a steady level with a time constant of approximately 450 ms that did not vary with potential. The currents were depressed by substituting cobalt or cadmium for extracellular calcium but similar effects were not obtained by substituting magnesium for calcium.     

Membrane potential of rat calvaria bone cells: dependence on temperature

The membrane potentials of bone cells derived from calvaria of new born rats was shown to be strongly dependent on temperature. When we lowered the temperature from 36 degrees C to 26 degrees C, cells with spontaneous resting membrane potentials (MP) of -80 to -50 mV depolarized (mean amplitude 8 mV; n = 33), and the membrane resistance increased by approximately 80% (n = 20). The temperature response depended on the actual MP, the reversal potential being in the range of -80 to -90 mV. With the application of ouabain (0.1-1 mmol/liter; n = 12), cells depolarized. Simultaneously, the reversal potential of the temperature response was shifted towards more positive values and approached the actual MP level of the cells. Consequently, the depolarization amplitudes induced by lowering temperature were reduced at spontaneous MP levels. The rise of the membrane resistance during cooling was unaffected. When the extracellular chloride concentration was reduced from 133 to 9 mmol/liter, temperature-dependent depolarizations persisted at spontaneous MP values (n = 5). The findings indicate that the marked effects of temperature changes on the MP of bone-derived cells are mainly determined by changes of the potassium conductance.     

Identification of the hyperpolarization-activated inward current in young embryonic chick heart myocytes

Whole-cell voltage-clamp experiments were performed to examine the underlying currents flowing during the pacemaker potential of spontaneously-beating embryonic chick ventricles. The holding potential was -30 mV. Long-duration (3 s) hyperpolarizing pulses were applied to -40 to -120 mV, in increments of 10 mV. A marked hyperpolarization-activated inward current (If) was produced. In cells from 3-day-old hearts, the threshold potential for the inward current was -50 to -60 mV. In 17-day-old cells, there was almost no If current. At -120 mV, the inward current was -93.8 +/- 6.3 pA (n = 5) in 3-day-old cells and -15.7 +/- 2.8 pA (n = 5) in 17-day-old cells. The average capacitances were 10.1 +/- 2.0 pF (n = 17) in 3-day-old cells, and 6.9 +/- 1.2 pF (n = 14) in 17-day-old cells. The reduction of If paralleled the decrease in spontaneous activity. In the presence of 3 mM CsCl, the inward current was blocked completely, and the tail current was reduced. In addition, 3 mM CsCl depressed the spontaneous action potentials and had a negative chronotropic effect. These results indicate that the hyperpolarization-activated inward If current exists in young embryonic chick heart cells, and decreases during development. This If current may contribute somewhat to the electrogenesis of the pacemaker potential.     

TRPC4 is an essential component of the nonselective cation channel activated by muscarinic stimulation in mouse visceral smooth muscle cells

Classical transient receptor potential channels (TRPCs) are thought to be candidates for the nonselective cation channels (NSCCs) involved in pacemaker activity and its neuromodulation in murine stomach smooth muscle. We aimed to determine the role of TRPC4 in the formation of NSCCs and in the generation of slow waves. At a holding potential of -60 mV, 50 mM carbachol (CCh) induced INSCC of amplitude [500.8+/-161.8 pA (n=8)] at -60 mV in mouse gastric smooth muscle cells. We investigated the effects of commercially available antibodies to TRPC4 on recombinant TRPC4 expressed in HEK cells and CCh-induced NSCCs in gastric smooth muscle cells. TRPC4 currents in HEK cells were reduced from 1525.6+/-414.4 pA (n=8) to 146.4+/-83.3 pA (n=10) by anti-TRPC4 antibody and INSCC amplitudes were reduced from 230.9+/-36.3 pA (n=15) to 49.8+/-11.8 pA (n=9). Furthermore, INSCC in the gastric smooth muscle cells of TRPC4 knockout mice was only 34.4+/-10.4 pA (n=8) at -60 mV. However, slow waves were still present in the knockout mice. Our data suggest that TRPC4 is an essential component of the NSCC activated by muscarinic stimulation in the murine stomach.     

Glucose depolarizes villous but not crypt cell apical membrane potential difference: a micropuncture study of crypt-villus heterogeneity in the rat

Brush-border membrane potentials and fractional resistances have been recorded from enterocytes at different points along the crypt-villus axis of rat ileum in vitro. Microelectrode impalements were obtained under visual control and brush-border membrane potentials were higher in crypt than in villous cells (-57 +/- 1.6 against -50 +/- 1.6 mV referred to the mucosal side). Replacing mannitol with D-glucose in the mucosal perfusate resulted in a rise in transmural potential difference (0.5 +/- 0.17 to 1.0 +/- 0.21 mV (n = 37)) and apical membrane potential was depolarized. This occurred consistently only in the upper two-thirds of the villus (-54 +/- 1.7 to -47 +/- 2.3 mV (n = 17)) and not in crypt cells (-56 +/- 2.6 to -57 +/- 2.4 mV (n = 10) or at the crypt-villus junction. The glucose-induced apical membrane depolarization in villous enterocytes was blocked by phlorizin, a competitive inhibitor of sodium-dependent glucose uptake (-50 +/- 2.1 to -53 +/- 2.8 mV (n = 9) in the presence of phlorizin and glucose). Transmural resistance, Rt, and fractional resistance, FR, were unaltered by glucose (61 +/- 3.4 to 61 +/- 3.5 omega X cm2 (n = 50] and (0.60 +/- 0.06 to 0.57 +/- 0.06 (n = 17]. This micro-puncture technique provides direct evidence for functional differentiation along the crypt-villus axis and indicates that active electrogenic accumulation of glucose is confined to villous epithelium.     

A packed Cytodex microbead array for three-dimensional cell-based biosensing

A packed Cytodex 3 microbead array was fabricated as a simple three-dimensional (3-D) cell-based biosensing format. Resting membrane potentials and voltage-gated calcium channel (VGCC) function of SH-SY5Y human neuroblastoma cells cultured on the microbead array versus collagen-coated flat (2-D) substrates were evaluated by confocal microscopy with a potentiometric dye, tetramethylrhodamine methyl ester, and a calcium fluorescent indicator, Calcium Green-1. SH-SY5Y cells, differentiated with 1mM dibutyryl cAMP and 2.5 microM 5-bromodeoxyuridine, showed significant resting membrane potential establishment on the topographical scaffolds in a period of 13 days into differentiation, in contrast to the previously reported insignificant resting membrane potential establishment of the same cells within collagen hydrogels. On days 2, 8 and 13 into differentiation, cells on collagen-coated flat substrates developed resting membrane potentials of -6.0+/-19.5 mV (n=198), -30.5+/-19.9 mV (n=191) and -21.7+/-18.9 mV (n=308), in contrast to values for cells on 3-D scaffolds of -25.8+/-14.7 mV (n=112), -37.6+/-13.1 mV (n=120) and -28.7+/-12.2 mV (n=158), respectively. The development of VGCC function, as measured by percentage of cells responsive to 50 mM high K(+) depolarization, was significantly slower for cells on 3-D scaffolds (20.0% on day 13 into differentiation) than for cells on 2-D substrates (30.7% on day 8 into differentiation). The exaggerated 2-D cell calcium dynamics, in comparison with those of 3-D cells, is consistent with previous 2-D/3-D comparative studies. This study established the rationale and feasibility of the microbead array format for 3-D cell-based biosensing.     

Transmembrane electrical characteristics of cultured human skeletal muscle cells

Skeletal muscle explants from normal subjects were established from biopsy material on collagen. Cellular outgrowth appeared within 3-4 days, and fusion of myoblasts was observed in 5-10 days. Multinucleated myotubes were impaled under high optical magnification, at 37 degrees C, with conventional glass microelectrodes. The mean resting potential was -44.4 mV +/- 2.4 (n = 399); -33 +/- 2.3 mV at 9 days (n = 10) vs -48 +/- 2.5 mV (n = 15) at 27 days. The average input resistance (Rin) was 9.7 M omega (n = 83). Action potentials could be elicited by electrical stimulation and had a mean amplitude of 55.9 +/- 2.1 mV with a mean maximum rate of rise (Vmax) of 72.1 +/- 7.5 V/s. The mean overshoot was 13.9 +/- 2.3 mV, and the action potential duration determined at 50% of repolarization (APD50) was 8.0 msec (n = 7). The resting membrane potential showed a depolarization of 23 mV/decade for extracellular potassium ion concentration ([K]o) between 4.5-100 mM. Thus, we have established the normal resting potential and maximum rate of rise of the action potential for human myotubes in culture. We have shown that the values for these are less than those previously reported in cultured avian and rodent cells. In addition, we have shown that the response in our system of the resting potential to change in extracellular potassium concentration is blunted compared to studies using isolated muscle, suggesting an increase in ratio of sodium to potassium permeability. Cultured human muscle cells depolarized in the presence of ouabain.     

Rescaled range analysis applied to the study delayed rectifier potassium channel kinetics

The gating of ion channels has widely been modeled by assuming that the transitions between open and closed states are a memoryless process. Nevertheless, analysis of records of unitary current events suggests that the kinetic process presents long lags (antipersistent correlation). Here, using the patch-voltage clamp technique and the rescaled range method, activity of single-channel delayed rectifier K(+) channels was studied. The experiment result showed that reversal potential was -73.3 mV in cell-attached mode. For the sequences of alternating open and shut time intervals, the Hurst coefficients were calculated for four different pipette potentials in rat dorsal root ganglion neurons. H=0.34169+/-0.00672 (n=4) for V=-30 mV; H=0.34632+/-0.0142 (n=3) for V=-40 mV; H=0.39237+/-0.0113 (n=4) for V=-50 mV; H=0.3954+/-0.0012 (n=4) for V=-60 mV. When the Hurst method was applied to the results from a simulated four-state Markovian model, it showed that it had different experimental data H coefficient, the distribution of the data values had no correlations between them, in particular, H=0.2531+/-0.00403 (n=50) for V=-40 mV. This indicates that open-dwell times and closed-dwell times are long lag (namely, antipersistent correlation) and do not change with the pipette potential applied to the patch.     

乙酰胆碱对蟾蜍背根神经节神经元膜电位的影响及离子机制

在离体灌流的蟾蜍背根神经节(DRG)标本上,用微电极进行胞内记录。在73个神经元中,依神经纤维的传导速度将神经元分为 A 型及 C 型,其中 A 型细胞67个,C 型6个,静息膜电位为-67.5±1.3mV((?)±SE)。当加4×10~(-4)—6×10~(-4)mol/L 乙酰胆碱(ACh),可观察到如下四种膜电位变化:1.超极化:幅值9.1±3.0mV((?)±SE,n=23);(2)去极化:幅值12.9±2.2mV((?)+SE,n=20);(3)双相反应(n=24):先超极化,后去极化,超极化幅值8.0±2.4mV((?)+SE),去极化幅值10.9±3.1mV((?)±SE);(4)无反应(n=6)。用阿托品(1.3×10~(-5)mol/L,n=23),或同时应用筒箭毒与六甲双铵(浓度均为1.4×10~(-5)mol/L,n=8)灌流,能分别阻断 ACh 引起的膜的超极化或去极化。ACh 引起超极化反应时膜电导平均增加13.8%,翻转电位值大约-96mV。四乙铵(TEA,20mmol/L)能使 ACh 的去极化幅值增加48.2±3.2%((?)±SE,n=6),超极化幅值减小79.4±4.3%((?)±SE,n=8)。MnCl_2(4mmol/L)使 ACh 的去极化及超极化幅值分别减小54.2±7.2%((?)±SE,n=5)及69.2±6.4%((?)±SE,n=14)。以上结果提示:ACh 引起的 DRG 神经细胞膜去极化反应由 N 型乙酰胆碱受体介导,而超极化反应由 Μ 型乙酰胆碱受体介导,前者可能包含了多种离子电导的改变,后者则可能与钾电导增加有关。     

血小板活化因子对豚鼠心室肌细胞动作电位和钾通道的影响

应用全细胞膜片钳技术研究了血小板活化因子(platelet activatingfactor,PAF)对豚鼠心室肌细胞动作电位和钾电流的影响.结果发现,当电极内液ATP浓度为5 mmol/L(模拟正常条件)时,1 μmol/L PAF使APD90由对照的225.8±23.3 ms延长至352.8±29.8ms(n=5,P＜0.05);使IK尾电流在指令电压 30 mV由对照的173.5±16.7 pA降至152.1±11.5 pA(P＜0.05,n=4);使Ikl在指令电压为-120 mV时由对照组的-6.1±1.3 nA降至-5.6±1.1 nA(P＜0.05,n=5);但PAF在生理膜电位范围(-90mV～ 20mV)对IK1没有影响.当电极内液ATP浓度为0mmol/L时,IK·ATP开放(模拟缺血条件),1 μmol/LPAF却显著缩短APD90,由对照的153±24.6 ms缩短至88.2±19.4 ms(n=5,P＜0.01).而用1 μmol/L格列本脲(IK·ATP的特异阻断剂)预处理后,恢复了PAF可显著延长动作电位时程的作用.结果提示,PAF可能扩大缺血心肌和正常心肌细胞动作电位时程的不均一性,是缺血/再灌注性心律失常发生的重要原因.