胃肠道平滑肌起搏电流产生机制的研究进展

越来越多的研究结果表明,Cajal间质细胞是胃肠道平滑肌慢波电位和自发性节律性收缩活动的起搏细胞.关于Cajal间质细胞起搏电流产生机制的研究近来进展很快,但仍存在一些分歧.本文就目前关于起搏电流的产生及传播机制的研究进展作一综述.     

Effects of alkaloids from Corydalis decumbens on contraction and electrophysiology of cardiac myocytes

The chloroform extract of Corydalis decumbens significantly increased the beating amplitude of cultured myocardial cell sheets. Chemical analysis led to the isolation of isoquinoline and protopine alkaloids. Of these isolated alkaloids, corlumidine and (+)-adlumidine increased the beating amplitude, but (+)-egenine decreased the beating rate and beating amplitude while protopine did not show any activity. We also studied the effects of (+)-egenine and corlumidine on contractile responses and Ca²⁺ currents in single bullfrog atrial cells using the voltage-clamp method. (+)-Egenine inhibited Ca²⁺ current by 68% of the control in single cell of bullfrog atrium, while corlumidine increased Ca²⁺ current to 60% at a concentration of 0.03 mM.     

芍药苷对心脏钾通道电生理功能的影响

目的研究芍药苷对内向整流钾电流(IK1)、瞬时外向钾电流(Ito)以及延迟整流钾电流(IKs和IKr)的作用。方法用全细胞膜片钳技术记录大鼠心室肌细胞的Ito和IK1电流。而IKs和IKr电流在转染相应质粒的HEK293细胞上记录。对比芍药苷使用前后的电流图,观察芍药苷对各种离子通道电流的影响。结果在-100mV测试电压下,100μmol/L的芍药苷能使IK1峰值密度从(-25.26±8.21)pA/pF降至(-17.65±6.52)pA/pF,平均抑制率为30.13%(n=6,P<0.05),但对其反转电位以及内向整流特性无影响。此外,100μmol/L芍药苷对Ito、IKs和IKr电流无明显作用。结论芍药苷对IK1电流具有明显的抑制作用,而对Ito、IKs及IKr无明显作用。     

Spontaneous transient inward currents and rhythmicity in canine and guinea-pig tracheal smooth muscle cells

Spontaneous transient inward currents (STICs) were recorded in canine and guinea-pig tracheal myocytes held at negative membrane potentials. STICs were Cl^– selective since their reversal potential was dependent on the Cl^– gradient and they were blocked by the Cl^– channel blocker niflumic acid. STICs were insensitive to Cs⁺, charybdotoxin, and nifedipine. Ca²⁺-activated K⁺ currents often preceded STICs, suggesting that the STICs are Ca²⁺ dependent. In support of this suggestion, we found the Cl^– currents were: (1) abolished by depleting intracellular Ca²⁺ stores using caffeine, acetylcholine, histamine, or substance P; (2) enhanced by increasing external concentrations of Ca²⁺; (3) evoked by voltage-dependent Ca²⁺ influx. The channels responsible for this Cl^– current are of small unitary conductance (<20 pS). Decay of the STICs was described by a single exponential with a time constant of 94±9 ms at –70 mV; the time constant increased considerably at more positive potentials. Using Ca²⁺-dependent Cl^– currents and contractions as indices of internal levels of Ca²⁺, we found that isolated tracheal cells are capable of exhibiting rhythmic behaviour: bursts of currents and contractions with a periodicity of less than 0.1 Hz and which continued for more than 20 min. These rhythmic events were recorded at negative membrane potentials, suggesting that cyclical release of internally sequestered Ca²⁺ is responsible. We conclude that spontaneous release of Ca²⁺ from intracellular stores in tracheal muscle cells leads to transient currents in some cases accompanied by rhythmic contractions. Our studies provide evidence for a cellular mechanism that could underly myogenic oscillations of membrane potential in smooth muscle.     

Ionic currents in cultured supraoptic neurons: Actions of peptides and transmitters

The hypothalamo-neurohypophysial system has proved an excellent model for peptidergic neurons in the central nervous system. Electrophysiological studies using in vivo and in vitro preparations with extracellular and intracellular recording techniques have determined some of the intrinsic and extrinsic mechanisms that generate the striking firing patterns that the neurons exhibit. We have developed a dissociated cell preparation of these neurons and used patch clamp recording techniques to enable detailed studies of membrane properties underlying such activities. Cultured neonatal supraoptic neurons fired spontaneous action potentials which in some cells were distinctively patterned. Under voltage clamp, voltage-activated Na⁺, K⁺, and Ca²⁺ currents were recorded. K⁺ and Ca²⁺ currents were modulated by application of -adrenergic agonists, and Ca²⁺ currents were also modulated by κ-opioid agonists. The neurons were also sensitive to γ-aminobutyric acid which acted directly on Cl-channels. Spontaneous, patterned activity, the presence of functional receptors for neurotransmitters and the ability to study the neurons under voltage clamp suggest that this is an excellent model system for studying these peptidergic neurons.     

Potentiation of PIEZO2 mechanically-activated currents in sensory neurons mediates vincristine-induced mechanical hypersensitivity

Vincristine,a widely used chemotherapeutic agent for treating different cancer,often induces severe peripheral neuropathic pain.A common symptom of vincristine-induced peripheral neuropathic pain is mechanical allodynia and hyperalgesia.However,mechanisms underlying vincristine-induced mechanical allodynia and hyperalgesia are not well understood.In the present study,we show with behavioral assessment in rats that vincristine induces mechanical allodynia and hyperalgesia in a PIEZO2channel-depen...     

肌膜与线粒体ATP敏感性钾离子通道对缺血预适应小鼠心肌保护的对比研究

目的:对比研究心肌肌膜和线粒体ATP敏感性钾通道(KA TP)在缺血预适应(IP)对小鼠体外心脏缺血/再灌注(I/R)损伤后梗死范围、心律失常和心功能的影响。方法:采用改良的Langendorff小鼠心脏灌注系统同步记录C57BL/6小鼠心脏心电图、左心室发展压和左心室压发展速率。选用特异性心肌肌膜KA TP阻断剂HMR109830μmol/L和特异性心肌线粒体KA TP阻断剂5HD500μmol/L。分对照组、IP组、IP加HMR1098组和IP加5HD组。IP组稳定16min后,行2个循环的IP,缺血2min和再灌注5min;然后缺血20min和再灌注45min,对照组无IP。在45min再灌注结束后,测定心肌梗死范围。结果:与对照组相比,IP组能显著降低心肌梗死范围,分别为(38·1±1·82)%和(29·4±2·71)%(P<0·05),但对心律失常积分和心功能恢复无明显影响。与IP组相比,IP加HMR1098组和IP加5HD组能显著增加心肌梗死范围和降低心功能,心肌梗死范围分别为(45·6±4·7)%和(51·1±5·2)%,但2组间差异无统计学意义。结论:IP对小鼠体外心脏I/R损伤具有保护作用,心肌肌膜和线粒体KA TP在IP后I/R损伤过程中均起重要作用。心肌梗死范围可作为IP保护心肌的可靠指标,但要慎重对待心律失常和心功能的变化。     

七氟醚麻醉对大鼠脑ATP酶的动态影响

目的 观察七氟醚吸入麻醉不同时期大鼠各脑区Na~ 、K~ -ATP酶和Ca~(2 )-ATP酶活性动态变化规律,以了解脑ATP酶活性变化在七氟醚麻醉效应中的地位。方法 40只SD大鼠随机均分为对照组、诱导期组、麻醉期组、恢复期组和清醒期组。分光光度法测定不同时期大脑皮质、脑干、海马Na~ 、K~ -ATP酶和Ca~(2 )-ATP酶活性变化。结果 与对照组比较,大鼠大脑皮质、脑干、海马Na~ 、K~ -ATP酶活性在诱导期分别降低21.9％、10.5％、19.3％(P<0.05),麻醉期分别降低37.2％、33.5％、38.9％(P均<0.01),恢复期又开始回升,但仍低于对照组水平(P<0.05或P<0.01),而清醒期基本恢复至对照组水平(P>0.05);大脑皮质、脑干、海马Ca~(2 )-ATP酶活性在诱导期分别降低34.3％、44.3％、25.5％(P<0.05 or P<0.01),麻醉期分别降低39.6％、60.4％、57.6％(P均<0.01),恢复期开始回升,清醒期基本恢复至对照组水平(P>0.05)。结论七氟醚对大鼠大脑皮质、脑干、海马Na~ 、K~ -ATP酶和Ca~(2 )-ATP酶活性的抑制程度与麻醉时相相对应,ATP酶活性与麻醉深度具有相同的变化趋势,表明上述脑区ATP酶可能是七氟醚的作用靶点,与七氟醚的麻醉效应有关。     

氯胺酮对离体大鼠心室肌细胞瞬时外向钾电流的影响

目的研究氯胺酮对大鼠心室肌细胞瞬时外向钾电流(Ito)的影响。方法酶解法分离大鼠心室肌细胞,采用全细胞膜片钳技术记录Ito,观察50μmol/L氯胺酮对Ito电流-电压曲线以及不同浓度氯胺酮对Ito的影响,并研究氯胺酮对Ito通道动力学的影响。结果钳制电压-40mV,刺激电压 70mV条件下,临床相关浓度的氯胺酮50μmol/L使Ito的电流峰值降低23·4%(P<0·01),冲洗后,Ito能够完全恢复。5、10、50、100、500、1000、5000μmol/L的氯胺酮抑制Ito呈浓度依赖性,电流抑制率分别为(13·8±9·7)%、(17·5±6·7)%、(23·4±8·8)%、(31·5±6·7)%、(63·3±5·5)%、(79·7±2·7)%、(88·9±4·4)%,其半数有效浓度(IC50)为299μmol/L。100μmol/L的氯胺酮对激活曲线没有影响;使Ito的失活曲线明显右移,半数失活电压(V1/2)在给药前后数值分别为(-28·27±0·20)mV和(-25·34±0·27)mV(P<0·01),斜率因子(k)值分别为(3·23±0·46)mV和(3·40±0·55)mV(P>0·05)。结论氯胺酮可明显阻滞大鼠心室肌的Ito,这是氯胺酮延长大鼠心室肌动作电位的机理之一,同时氯胺酮使Ito的失活曲线右移。     

Potassium channel subtypes as molecular targets for overactive bladder and other urological disorders

Potassium channels have re-emerged as attractive targets for overactive bladder and other urological diseases in recent years, in part due to an enhanced understanding of their molecular heterogeneity, tissue distribution, functional roles and regulation in physiological and pathological states. Cloning and heterologous expression analysis, coupled with the advancement of improved high-throughput screening techniques, have enabled expeditious identification of selective small-molecule openers and blockers for ATP-sensitive K⁺ channels, Ca²⁺-activated K⁺ channels and voltage-dependent K⁺ channel-KQT-like subfamily (KCNQ) members, and has paved the way in the assessment of efficacy and adverse effects in preclinical models. This review focuses on the rationale for molecular targeting of K⁺ channels, the current status of target validation, including preclinical proof-of-concept studies, and provides perspectives on the limitations and hurdles to be overcome in realising the potential of these targets for diverse urological indications such as overactive bladder, erectile dysfunction and prostate diseases.