豚鼠离体腹腔神经节神经元自发f-EPSP和AP

应用细胞内生物电记录技术观察豚鼠腹腔神经节(CG)神经元自发快兴奋性突触后电位(f-EPSP)和动作电位(AP)的特征,分析其形成的可能机制。发现在豚鼠离体CG上存在自发f-EPSP和AP,发放频率不同。自发f-EPSP的幅度(5.67±2.66)mV(n=26),明显低于刺激内脏大神经诱发f-EPSP的幅度(13.26±6.74)mV(n=34,P<0.01),而自发的AP后超极化幅度(AHPA)(13.86±4.24)mV(n=30),明显高于刺激内脏大神经诱发的AHPA(8.99±2.79)mV(n=54,P<0.01)。六烃季铵或低Ca2 /高Mg2 Krebs液能完全阻断自发的AP,但自发的f-EPSP则不被完全阻断。结果提示豚鼠离体CG神经元有自发性电活动,这除与突触前膜ACh的随机释放有关以外,可能还有对Ca2 不敏感的其他递质介导。     

新生大鼠脊髓切片运动神经元的电生理参数测定

用微电极技术对新生大鼠脊髓横切薄片运动神经元(MN)进行细胞内记录,测得静息电位为-62±4mV(n=26),膜电阻为67±31MΩ,时间常数3.8±1.6ms,动作电位幅度68±7mV(n=26),阈电位-50±8mV,超射值6±4mV。灌流谷氨酸(1～30mmol/L)诱导伴膜电阻降低的缓慢去极化反应,5-羟色胺(50μmol/L)介导伴膜电导降低的电压依赖性内向电流。结果表明新生大鼠脊髓切片MN的细胞内生物电记录是一种稳定可靠的电生理学和药理学研究方法。     

豚鼠冠状动脉微动脉细胞静息膜电位的分布特性及机制

目的:观察冠状动脉微动脉细胞静息膜电位(RP)的分布特性及形成机制.方法:离体豚鼠冠状动脉微动脉(直径小于100 μm)上,应用细胞内微电极技术记录细胞RP.结果:①成功记录到112个细胞,细胞平均RP为(-65±4.2)mV,应用高斯函数拟合后细胞RP呈双峰状分布,两个峰值分别为-43和-74 mV,分别称为高和低R...     

大鼠背根节神经元后超极化中Ca2+激活 K+电流的蜂毒明肽敏感成分ⅠAHP

为了明确大鼠背根节(DRG)神经元中存在慢的Ca2+激活K+电流成分,本实验在新鲜分散的DRG神经元胞体上,采用全细胞电压箝技术,给予DRG神经元一定强度的去极化刺激,记录刺激结束后30 ms时的尾电流幅度.结果发现:(1)随着去极化时间从1 ms延长至180 ms时,尾电流幅度由9.3±2.8 pA逐渐增大至64.1±3.4 pA(P＜0.001);(2)当去极化结束后的复极化电位降低时,尾电流幅度先逐渐下降到零,然后改变方向,逆转电位约为-63 mV;(3)细胞外施加500μmol/L Cd2+或细胞内液中施加11 mmol/L EGYA时尾电流明显减小甚至完全消失;(4)尾电流中慢成分的幅度在细胞外给与200 nmol/L蜂毒明肽后,减小了约26.32±3.9%(P＜0.01);(5)细胞外施加10 mmol/L TEA,可明显降低尾电流中的快成分.结果提示,在DRG神经元后超极化中存在Ca2+激活K+电流的蜂毒明肽敏感成分--ⅠAiHP.     

低镁和缺镁对离体豚鼠右心室肌单细胞动作电位的效应

取豚鼠右心室肌,在改良 Krebs 溶液灌注下,用微电极记录动作电位(AP)12只豚鼠72次心肌单细胞 AP 有关参数的平均值为:静息电位(RP)-76±9mV;动作电位振幅(APA)107±7mV;动作电位时程(APD)_(_30mv)为254±123ms;APD_(100)为312±133ms。当灌注液中镁离子浓度减低到0.6mol/L 时,72次 AP 的 APD_(_30mv)和APD_(100)分別为对照值的80.7%和83%;在无镁溶液中,改变更为显著,分别为对照值的70.9%和76.7%;RP 和 APA 则变化均不大。实验提示:低镁可使 APD 缩短,从而可能影响体表心电图 T 波的第3位相;此外,APD 的缩短意味着不应期相对缩短,这或许是低镁症时出现室性早搏的因素。     

大鼠背根节神经元后超极化中Ca~(2 )激活K~ 电流的蜂毒明肽敏感成分I_(AHP)

为了明确大鼠背根节（DRG）神经元中存在慢的Ca2 激活K 电流成分,本实验在新鲜分散的DRG神经元胞体上,采用全细胞电压箝技术,给予DRG神经元一定强度的去极化刺激,记录刺激结束后30ms时的尾电流幅度。结果发现：（1）随着去极化时间从1ms延长至180ms时,尾电流幅度由9．3±2．8pA逐渐增大至64.1±3．4pA（P＜0．001）;（2）当去极化结束后的复极化电位降低时,尾电流幅度先逐渐下降到零,然后改变方向,逆转电位约为-63mV;（3）细胞外施加500μmol／LCd2 或细胞内液中施加11mmol／LEGTA时尾电流明显减小甚至完全消失;（4）尾电流中慢成分的幅度在细胞外给与200nmol／L蜂毒明肽后,减小了约26.32±3。9％（P＜0。01）;（5）细胞外施加10mmol／LTEA,可明显降低尾电流中的快成分。结果提示,在DRG神经元启超极化中存在Ca2 激活K 电流的蜂毒明肽敏感成分──IAHP。     

大鼠背根节神经元后超极化中Ca^2＋激活K^＋电流的蜂毒明肽敏感成分 …

为了明确大鼠背根节(DRG)神经元中存在慢的Ca2+激活K+电流成分,本实验在新鲜分散的DRG神经元胞体上,采用全细胞电压箝技术,给予DRG神经元一定强度的去极化刺激,记录刺激结束后30 ms时的尾电流幅度.结果发现:(1)随着去极化时间从1 ms延长至180 ms时,尾电流幅度由9.3±2.8 pA逐渐增大至64.1±3.4 pA(P＜0.001);(2)当去极化结束后的复极化电位降低时,尾电流幅度先逐渐下降到零,然后改变方向,逆转电位约为-63 mV;(3)细胞外施加500μmol/L Cd2+或细胞内液中施加11 mmol/L EGYA时尾电流明显减小甚至完全消失;(4)尾电流中慢成分的幅度在细胞外给与200 nmol/L蜂毒明肽后,减小了约26.32±3.9%(P＜0.01);(5)细胞外施加10 mmol/L TEA,可明显降低尾电流中的快成分.结果提示,在DRG神经元后超极化中存在Ca2+激活K+电流的蜂毒明肽敏感成分--ⅠAiHP.     

三叉神经中脑核神经元膜的电学特性

用大鼠脑干脑片,给三叉神经中脑核79个神经元作了细胞内记录,测算了20个神经元膜的电学特性:静息电位-60.3±5.6mV;输入阻抗为10.5±5.4MΩ;时间常数1.3±0.5ms。电刺激可诱发动作电位,测算32个神经元的有关参数:阈电位-50—-55mV;波幅69.5±6.1mV;超射11.9±3.6mV;波宽0.8±0.2ms。TTX(0.3μmol/L)或无钠使之消失。通以长时程矩形波电流可引起200—250Hz的2—15个重复放电,但在通电停止前终止,TEA或4-AP可延长放电。膜电位-60—-55mV时在动作电位之后可看到阈下电位波动,它不受TTX的影响,无钙时消失,TEA或4-AP使波幅增大。静息电位去极化可使45个神经元中的40个发生外向整流作用,并被TEA,4-AP或无钙抑制,超极化则发生内向整流作用,Cs或无钠抑制之。灌流液中加入各种钾通道阻断药时神经元的稳态I-V曲线发生相应变化,提示I_(DR),l_A,I_(K(Ca))及I_Q可能都与静息时的膜电导有关。     

大鼠下丘脑薄片视上核神经元的细胞内生物电记录

从成年Ｓｐｒａｇｕｅ－Ｄａｗｌｅｙ大鼠用振动切片机制备含有视上核的下丘脑冠状薄片（５００μｍ厚）,并对视上核神经元（ｎ＝１７）进行常规细胞内生物电记录。测得静息电位－６０±８ｍＶ,膜输入电阻１７３±５８ＭΩ,时间常数１０．２±３．９ｍｓ,动作电位幅度６５±１２ｍＶ,阈电位－４４±７ｍＶ,由Ｉ─Ｖ曲线测得斜率电阻１５８±６２ＭΩ,大部分细胞还显示内向整流特性。在静息电位状态下,５７％细胞保持静息,４３％有自发锋电位发放。细胞的锋电位发放模式７８％为时相型,２２％为持续型。外源性去甲肾上腺素（ｎ＝７）或谷氨酸钠（ｎ＝５）可引起伴有膜电阻减小的去极化反应,并可导致锋电位的串发放。     

去甲肾上腺素引起蟾蜍背根神经节神经细胞膜电位变化的离子机制

本文应用细胞内记录方法,对去甲肾上腺素(NA)引起蟾蜍背根神经节(DRG)神经细胞膜电位去极化或超极化反应时的膜电导及翻转电位值进行了测量,并观察了钾和钙离子通道阻断剂灌流DRG对NA引起膜电位反应的影响。当NA引起去极化反应时,15个细胞的膜电导减小32.6％。少数细胞膜电导开始增加,继而减小(n=4)。NA超极化反应时膜电导增加13.2％(n=8)。NA去极化反应的翻转电位值为-88.5±0.9mV((?)±SE,n=4),NA超极化反应在膜电位处于-89至-92mV时消失。 钾通道阻断剂四乙铵可使NA去极化幅值增加73.7±11.9％((?)±SE,n=7),并使NA超极化幅值减小40.5％(n=4)。细胞内注入氯化铯使苯肾上腺素去极化幅值增加34.5％(n=4)。钙通道阻断剂氯化锰使NA去极化及超极化反应分别减小50.5±9.9％((?)±SE,n=10)和89.5±4.9％((?)±SE,n=7)。结果提示,NA引起DRG神经细胞膜电位的去极化或超极化反应,可能与膜的钾及钙通道活动的改变有关。     

Augmentation and suppression of action potentials by estradiol in the myometrium of pregnant rat.

The purpose of this study was to investigate the actions of estradiol on spontaneous and evoked action potentials in the isolated longitudinal smooth muscle cells of the pregnant rat. Single cells were obtained by enzymatic digestion from pregnant rat longitudinal myometrium. Action potentials and currents were recorded by whole-cell current-clamp and voltage-clamp methods, respectively. The acute effects of 17beta-estradiol on action potentials and inward and outward currents were investigated. The following results were obtained. The average resting membrane potential of single myometrial cells was -54 mV (n = 40). In many cells, an electrical stimulation evoked a membrane depolarization, and action potentials were superimposed on the depolarization. In some cells, spontaneous action potentials were observed. Estradiol (30 microM) slightly depolarized the membrane (ca. 5 mV) and attenuated the generation of action potentials by reducing the frequency and amplitude of the spikes. Afterhyperpolarization was also attenuated by estradiol (30 microM). On the other hand, in 5 of 35 cells, estradiol increased the first spike amplitude and action potential duration, while frequency of the spike generation and afterhyperpolarization were inhibited. In voltage-clamped muscle cells, estradiol inhibited both inward and outward currents. Acute inhibition or augmentation of spike generation by estradiol is due to the balance of inhibition of inward and outward currents. Inhibition of both currents also prevented afterhyperpolarization, causing potential-dependent block of Ca spikes.     

Basic electrophysiological parameters and frequency sensitivity of the ventricular myocardium of human embryos

The basic electrophysiological manifestations of the ventricular myocardium of twelve 7- to 12-week human embryos were measured with a glass electrode and a programmed stimulation technique. The resting membrane potential value was 79.37 +/- 0.34 mV and the overshoot 32.7 +/- 0.57 mV; the action potential (AP) duration at 1 Hz stimulation frequency was 120.0 +/- 5.7 ms at AP plateau phase levels and 258 +/- 17 ms at the level corresponding to 95% repolarization. The duration of the AP was a function of the stimulation frequency. i.e. it altered in correlation to the stimulation programme fully developed frequency sensitivity). In stimulation with different frequencies the duration of the steady state AP was in an inverse relation to the stimulation frequency, the maximum changes being found in the terminal repolarization zone. An interpolated extrasystole mainly affected the duration of the plateau phase.     

Electrical properties of neurons recorded from the rat supraoptic nucleus in vitro

The electrical properties of neurons in the supraoptic nucleus (so.n.) have been studied in the hypothalamic slice preparation by intracellular and extracellular recording techniques, with Lucifer Yellow CH dye injection to mark the recording site as being the so.n. Intracellular recordings from so.n. neurons revealed them to have an average membrane potential of -67 +/- 0.8 mV (mean +/- s.e.m.), membrane resistance of 145 +/- 9 M omega with linear current-voltage relations from 40 mV in the hyperpolarizing direction to the level of spike threshold in the depolarizing direction. Average cell time constant was 14 +/- 2.2 ms. So.n. action potentials ranged in amplitude from 55 to 95 mV, with a mean of 76 +/- 2 mV, and a spike width of 2.6 +/- 0.5 ms at 30% of maximal spike height. Both single spikes and trains of spikes were followed by a strong, long-lasting hyperpolarization with a decay fitted by a single exponential having a time constant of 8.6 +/- 1.8 ms. Action potentials could be blocked by 10(-6) M tetrodotoxin. Spontaneously active so.n. neurons were characterized by synaptic input in the form of excitatory and inhibitory postsynaptic potentials, the latter being apparently blocked when 4 M KCl electrodes were used. Both forms of synaptic activity were blocked by application of divalent cations such as Mg2+, Mn2+ or Co2+. 74% of so.n. neurons fired spontaneously at rates exceeding 0.1 spikes per second, with a mean for all cells of 2.9 +/- 0.2 s-1. Of these cells, 21% fired slowly and continuously at 0.1 - 1.0 s-1, 45% fired continuously at greater than 1 Hz, and the remaining 34% fired phasically in bursts of activity followed by silence or low frequency firing. Spontaneously firing phasic cells showed a mean burst length of 16.7 +/- 4.5 s and a silent period of 28.2 +/- 4.2 s. Intracellular recordings revealed the presence of slow variations in membrane potential which modified the neuron's proximity to spike threshold, and controlled phasic firing. Variations in synaptic input were not observed to influence firing in phasic cells.     

Role of Ca2+-activated Cl- channels and MLCK in slow IJP in opossum esophageal smooth muscle

The possible contribution of Ca2+-activated Cl- channel [I(Cl(Ca))] and myosin light-chain kinase (MLCK) to nonadrenergic, noncholinergic slow inhibitory junction potentials (sIJP) was studied using conventional intracellular microelectrode recordings in circular smooth muscle of opossum esophageal body and guinea pig ileum perfused with Krebs solution containing atropine (3 microM), guanethidine (3 microM), and substance P (1 microM). In opossum esophageal circular smooth muscle, resting membrane potential (MP) was -51.9 +/- 0.7 mV (n = 89) with MP fluctuations of 1-3 mV. A single square-wave nerve stimulation of 0.5 ms duration and 80 V induced a sIJP with amplitude of 6.3 +/- 0.2 mV, half-amplitude duration of 635 +/- 19 ms, and rebound depolarization amplitude of 2.4 +/- 0.1 mV (n = 89). 9-Anthroic acid (A-9-C), niflumic acid (NFA), wortmannin, and 1-(5-chloronaphthalene-1-sulfonyl)-1H-hexahydro-1,4-diazepine (ML-9) abolished MP fluctuations, sIJP, and rebound depolarization in a concentration-dependent manner. A-9-C and NFA but not wortmannin and ML-9 hyperpolarized MP. In guinea pig ileal circular smooth muscle, nerve stimulation elicited an IJP composed of both fast (fIJP) and slow (sIJP) components, followed by rebound depolarization. NFA (200 microM) abolished sIJP and rebound depolarization but left the fIJP intact. These data suggest that in the tissues studied, activation of I(Cl(Ca)), which requires MLCK, contributes to resting MP, and that closing of I(Cl(Ca)) is responsible for sIJP.     

Electrophysiological control of ciliary motor responses in the ctenophorePleurobrachia

Prey capture by a tentacle of the ctenophore Pleurobrachia elicits a reversal of beat direction and increase in beat frequency of comb plates in rows adjacent to the catching tentacle (Tamm and Moss 1985). These ciliary motor responses were elicited in intact animals by repetitive electrical stimulation of a tentacle or the midsubtentacular body surface with a suction electrode. An isolated split-comb row preparation allowed stable intracellular recording from comb plate cells during electrically stimulated motor responses of the comb plates, which were imaged by high-speed video microscopy. During normal beating in the absence of electrical stimulation, comb plate cells showed no changes in the resting membrane potential, which was typically about -60 mV. Trains of electrical impulses (5/s, 5 ms duration, at 5-15 V) delivered by an extracellular suction electrode elicited summing facilitating synaptic potentials which gave rise to graded regenerative responses. High K+ artificial seawater caused progressive depolarization of the polster cells which led to volleys of action potentials. Current injection (depolarizing or release from hyperpolarizing current) also elicited regenerative responses; the rate of rise and the peak amplitude were graded with intensity of stimulus current beyond a threshold value of about -40 mV. Increasing levels of subthreshold depolarization were correlated with increasing rates of beating in the normal direction. Action potentials were accompanied by laydown (upward curvature of nonbeating plates), reversed beating at high frequency, and intermediate beat patterns. TEA increased the summed depolarization elicited by pulse train stimulation, as well as the size and duration of the action potentials. TEA-enhanced single action potentials evoked a sudden arrest, laydown and brief bout of reversed beating. Dual electrode impalements showed that cells in the same comb plate ridge experienced similar but not identical electrical activity, even though all of their cilia beat synchronously. The large number of cells making up a comb plate, their highly asymmetric shape, and their complex innervation and electrical characteristics present interesting features of bioelectric control not found in other cilia.     

Acute actions of marine toxin latrunculin A on the electrophysiological properties of cultured dorsal root ganglion neurones

The effects of latrunculin A, isolated from the nudibranch Chromodoris sp., on the excitability of neonatal rat cultured dorsal root ganglion neurones were investigated using patch-clamp recording and Ca(2+) imaging techniques. Under current-clamp conditions, acute application of latrunculin A (100 microM) reversibly induced multiple action potential firing and significantly increased action potential duration. No significant effects on action potential peak amplitude, threshold of action potential firing, resting membrane potential and input resistance were observed. Under voltage-clamp conditions, significant and dose-dependent suppression of K(+) current was seen with 10-100 microM latrunculin A. Additionally, a significant difference between inhibition of the current measured at the peak and the end of a 100 ms voltage step was seen with 100 microM latrunculin A. Fura-2 fluorescence Ca(2+) imaging revealed that latrunculin A (100 microM) significantly inhibited Ca(2+) transients evoked by KCl-induced depolarisation in all neurones. In 36% of DRG neurones, latrunculin A alone had no effect on intracellular Ca(2+). In 64% of neurones, latrunculin A alone evoked a transient rise in intracellular Ca(2+). Moreover, latrunculin A (10-100 microM) significantly inhibited the mean high voltage-activated Ca(2+) current. The effects of latrunculin A on action potential firing and K(+) currents were attenuated by intracellular phalloidin, an indication that these effects are mediated through actin disruption.     

Glial potentials in hippocampus

In rats under urethane anaesthesia, intracellular recordings were made from 36 cells, mainly in CA1, that had all the characteristics of glia: unusually high and stable resting potentials (-79.6 +/- 6.0 mV, mean +/- SD) and total absence of spikes or synaptic potentials. They were exceptionally sensitive to surrounding neuronal activity, being readily depolarized by very low frequency stimulation (0.5-2 Hz) of the fimbria. In the range 0.5-2 Hz, the mean peak depolarizations increased linearly with frequency of fimbrial stimulation (9.1 +/- 0.53 mV/Hz). At frequencies of 5 Hz or more, the depolarizations were highly variable, sometimes reaching a maximum of 25-30 mV, but the overall mean was not significantly greater than for 2 Hz stimulation. The depolarizations decayed slowly, with a half-time of 4.2 +/- 1.22 s and were often followed by a prolonged undershoot (lasting over 1 min). Alvear and especially septal stimulation were much less effective in evoking glial depolarizations. One cell that initially had all the characteristics of a glia, during very prolonged stable recording, developed responses, such as synaptic potentials and 20-40 mV action potentials evoked by fimbrial or alvear stimulation, consistent with strong electrical coupling to at least one neighbouring neuron.     

Cav1.2 calcium channels modulate the spiking pattern of hippocampal pyramidal cells

Ca(v)1.2 L-type calcium channels support hippocampal synaptic plasticity, likely by facilitating dendritic Ca2+ influx evoked by action potentials (AP) back-propagated from the soma. Ca2+ influx into hippocampal neurons during somatic APs is sufficient to activate signalling pathways associated with late phase LTP. Thus, mechanisms controlling AP firing of hippocampal neurons are of major functional relevance. We examined the excitability of CA1 pyramidal cells using somatic current-clamp recordings in brain slices from control type mice and mice with the Ca(v)1.2 gene inactivated in principal hippocampal neurons. Lack of the Ca(v)1.2 protein did not affect either affect basic characteristics, such as resting membrane potential and input resistance, or parameters of single action potentials (AP) induced by 5 ms depolarising current pulses. However, CA1 hippocampal neurons from control and mutant mice differed in their patterns of AP firing during 500 ms depolarising current pulses: threshold voltage for repetitive firing was shifted significantly by about 5 mV to more depolarised potentials in the mutant mice (p<0.01), and the latency until firing of the first AP was prolonged (73.2+/-6.6 ms versus 48.1+/- 7.8 ms in control; p<0.05). CA1 pyramidal cells from the mutant mice also showed a lowered initial spiking frequency within an AP train. In control cells, isradipine had matching effects, while BayK 8644 facilitated spiking. Our data demonstrate that Ca(v)1.2 channels are involved in regulating the intrinsic excitability of CA1 pyramidal neurons. This cellular mechanism may contribute to the known function of Ca(v)1.2 channels in supporting synaptic plasticity and memory.     

大鼠前庭内侧核在前庭—交感反应中的作用

实验在氯醛糖和尿酯混合麻醉的大鼠上进行。在内脏大神经上记录刺激同侧前庭神经进入脑干处的交感反应。电刺激前庭神经可在同侧内脏大神经引出—明确的叠加反应,其平均潜伏期为45.8±6.98ms,时程为55.21±5.35ms。增加刺激强度,反应幅度也增加,但潜伏期不变。用前庭内侧核(NVM)的片层场电位作为指标并选择其相位倒转处作刺激点,可在同侧内脏大神经记录到潜伏期为32ms 的叠加反应,而同一动物刺激前庭神经入脑处时内脏大神经反应的潜伏期为43ms。在 NVM 头端损毁后,此前庭-交感反应明显减小,再损毁尾端 NVM 后,此反应消失。损毁 Deiters 核对前庭-交感反应无影响。这些结果表明 NVM在内脏大神经记录到的前庭-交感反应中是一重要的中继站。