不同剂量甘丙肽拮抗剂M35在中枢引致的相反效应

目的:在三叉神经主核(ＰｒＶ)上检测不同剂量甘丙肽拮抗剂Ｍ３５的中枢效应。方法:运用全细胞膜片钳技术。结果:运用Ｍ３５ ０．０１μｍｏｌ·Ｌ－１、０．０３μｍｏｌ·Ｌ－１及０．１μｍｏｌ·Ｌ－１时,甘丙肽引发的外向性电流分别抑制 ３２．８%、７０．７%及７７．６%,Ｍ３５１ μｍｏｌ·Ｌ－１及３ μｍｏｌ·Ｌ－１使甘丙肽外向性电流分别增大 ２８．４%及 ４９．１%。结论:Ｍ３５低浓度为甘丙肽拮抗剂,Ｍ３５高浓度有甘丙肽激动剂作用,ＰｒＶ同一神经元上可能存在不同甘丙肽亚型受体。     

甘丙肽与学习记忆

甘丙肽是1983年发现的一种脑肠肽，与认知情感和内稳态的调节密切相关。本文着重综述了甘丙肽对多种学习记忆功能的抑制及调节学习记忆功能的机制：甘丙肽的过度表达破坏了学习记忆相关部位去甲肾上腺素、5-羟色胺和乙酰胆碱的平衡，使学习记忆功能处于病理状态；兴奋胆碱能M2突触前受体，反馈性减少乙酰胆碱释放；引起神经细胞膜超极化及外向性钾离子流，产生抑制性突触后电位，抑制乙酰胆碱释放；降低突触前膜兴奋性谷氨酸释放，损伤突触可塑性；甘丙肽受体是G蛋白偶联受体，甘丙肽在受体活化下游抑制腺苷酸化环化酶及转录因子CREB结合启动子，影响新的基因和蛋白表达，从而阻断短时记忆转入长时记忆。临床上在阿尔茨海默病和Down’s综合征等神经变性性疾病中，围绕Meynert基底核和斜角带核胆碱能神经元周围甘丙肽纤维和终末数量大大增加，提示使用甘丙肽拮抗剂治疗的可能。     

老龄房颤犬模型静脉肌袖细胞分离及起搏电流记录

背景：电生理改变是老化心脏表现的主要特征之一。 目的：构建老龄房颤犬模型，观察静脉肌袖细胞动作电位和起搏电流的特征。 设计、时间及地点：分组对照动物实验，于2005-03/2007-12在解放军总医院实验动物中心和老年心血管病研究所完成。 材料：7~9岁健康杂种老龄犬12只，体质量15~20 kg，雌雄兼有。台氏液成分(mmol/L)：NaCl 135, KCl 5.4, CaCl2 1.8, MgCl2 1, NaH2PO4 0.33, HEPES 10, 葡萄糖10, pH 用NaOH 调至 7.4。 方法：取老龄犬6只，快速起搏8周制备房颤模型，余6只犬未经快速起搏处理作对照。分离静脉肌袖细胞，利用全细胞膜片钳在电流钳模式下记录动作电位，在电压钳模式下记录起搏电流。 主要观察指标：老龄犬肺静脉肌袖细胞动作电位的特征、起搏电流、起搏电流的Ⅰ~Ⅴ曲线及起搏电流稳态激活的特征。 结果：约82.6％的老龄犬静脉肌袖细胞记录到自动除极和自发性动作电位，而未经快速起搏处理犬的细胞约有40%记录到工作心肌动作电位特征。在-120 mV时，房颤模型细胞起搏电流的电流密度为(-2.66±0.4) pA/pF，而对照组细胞的电流密度为(-1.24±0.21) pA/pF。从Ⅰ~Ⅴ曲线可见，起搏电流的电流密度具有电压依赖性特征，且病理模型犬的肺静脉肌袖细胞起搏电流电流随超极化电位增加更为明显。在-120 mV时，房颤犬静脉肌袖细胞电流的半激活电压为(-84.3±4.9)mV，激活曲线斜率为(+12.1±2.6) mV，而未处理细胞的半激活电压为(-98.0±7.2) mV，激活曲线斜率为(+9.5±1.8) mV，明显向更正的电位方向移动，提示老龄房颤犬静脉肌袖起搏电流更易激活。 结论：老龄房颤犬静脉肌袖细胞更易出现自动除极电位，起搏电流的密度更高，起搏电流激活也更容易，提示起搏电流可能参与老年房颤异位起搏的发生。     

星形胶质细胞诱导成年大鼠骨髓基质细胞分化前后的电生理功能鉴定

目的 探讨骨髓基质细胞向神经元方向分化后是否具备神经元的电生理功能。方法 应用膜片钳技术,釆用全细胞记录方式.对由星形胶质细胞诱导的分化前、分化3d、分化7d的成年大鼠骨髓基质细胞进行电生理功能测定。结果分化前后的骨髓基质细胞未记录到内向Na~+电流,但成功记录到了静息膜电位,分別为:(-12.71±3.25)mV(n=7)、(-26.29±10.34)mV(n=7)、(-45.0±8.46)mV(n=6);刺激脉冲为40 mV时三组的外向延迟整流K~+电流分別为:(0.31±0.17)nA(n=7)、(1.34±0.59)nA(n=8)、(1.99±0.97)nA(n=7);刺激脉冲为-40 mV时的内向整流K~+电流为:(79±58)pA(n=7)、(260±150)pA(n=8)、(420±120)pA(n=7),伴随着分化时间的逐渐延长,两种K~+电流及膜电位逐渐增高。结论(1)骨髓基质细胞表达弱的外向延迟整流K~+电流及内向整流K~+电流可能是其特征性的电生理指标。(2)骨髓基质细胞经过星形胶质细胞的诱导能够向功能性神经元方向分化。     

硬脑膜传入神经末梢敏化对初级感觉神经元电压门控型钙电流的影响

目的 探讨化学刺激硬脑膜传入神经末梢对大鼠三叉神经节神经元的高电压激活钙电流(HVA-ICa)的调控效应. 方法 雄性SD大鼠16只按随机数字表法分为生理盐水(NS)组和致炎剂(IS)+释放降钙素基因相关肽(CGRP)组(n=8),大鼠上矢状窦处脑膜给药造模1h后急性分离大鼠三叉神经节中小神经元,采用全细胞膜片钳技术记录电压门控钙离子通道(VGCC)电流. 结果 与NS组钙电流峰电流[(-49.5±5.18)pA/pF]比较,IS+CGRP组[(-80.48±4.43) pA/pF]增高,差异有统计学意义(P＜0.05);IS+CGRP组神经元钙电流激活曲线的半数激活电压Val/2为(-20.9±0.4)mV,较NS组[(-16.2±0.5)mV]向超级化方向移动了4.7 mV,差异有统计学意义(P＜0.05); IS+CGRP组神经元钙电流的半数失活电压V1/2为(-12.4±0.2) mV,较NS组[(-22.5±0.3)mY]向去极化方向移动了10.1 mV,差异有统计学意义(P＜0.05). 结论 激活硬脑膜传入神经末梢诱导初级感觉神经元的外周敏化过程,突出表现为钙电流的增高.     

双分离法记录Wistar大鼠神经元的全细胞电流

背景：细胞培养与通道电流记录是全细胞膜片钳实验的主要难点。 目的：介绍一种简单可行的降低全细胞膜片钳实验方法，将细胞急性分离与电流的分离技术结合起来，以提高工作效率，缩短实验的时间，从根本上降低膜片钳实验的难度。 方法：SPF级出生4~7 d的wistar大鼠40只，雌雄不限。采用改良的急性分离的方法制备Wistar大鼠脑皮质细胞，将大鼠脑皮质切成400~600 μm厚度的薄片，在人工脑脊液中通混合气静止1 h，并通以氧气。将脑组织块放入含有16 u/mL( type X )和2 u/mL(type XIV) 蛋白水解酶的人工脑脊液中，孵育60 min，清除消化酶。在全细胞电压钳制模式下，保持电位 -80 mV，给予-60 mV到60 mV的去极化脉冲刺激，步阶为+10 mV，刺激波宽160 ms。记录到跨膜总电流，在全细胞电极液里面加入70 mmol/LCsCl，70 mmol/L CsF；在外液中先后加入11 μmol/L 阻断剂河豚毒素、30 mmol/L的氯化四乙胺、1 mmol/L的4-AP。分别记录内向钠电流，瞬时外向钾电流和延迟整流钾电流，结果用clampfit分析处理。主要观察：①细胞的形态学观察。②全细胞电流的记录。③内向钠电流的记录。④外向钾电流的记录。 结果与结论：细胞空间立体结构强，表面光滑，有完整的树突或者轴突，且细胞的活性可以在25 ℃室温下维持8~10 h。在外液中加入1 μmol/L的河豚毒素基本上可以阻断钠电流；30 mmol/L的氯化四乙胺和1 mmol/L的4-AP可以阻断外向钾电流。结果表明，改良的细胞急性分离方法细胞功能完好。通过电流分离技术，不改变细胞外液和电极液，仅需添加特异阻断剂，可记录到内向钠电流，瞬时外向钾电流以及延迟整流钾电流，较之传统方法可显著提高工作效率。     

大鼠伏隔核神经元膜特性及乙醇对其影响

目的 :观察伏隔核神经元的膜特性及致醉剂量的乙醇 (44mmol L)对其影响。 方法 :在大鼠伏隔核脑片上 ,采用细胞内电流钳记录技术。结果 :所观察到的神经元包括五种类型 ,神经元的静息膜电位 (mV)为 - 79.1± 2 .4 ,输入阻抗 (MΩ)为 4 8.4± 2 .3,锋电位的幅度 (mV)平均为 98.5± 4 .1;致醉剂量的乙醇 (44mmol L)对大部分伏隔核神经元的膜电位、输入阻抗及I V曲线无明显影响。 结论 :在伏隔核内 ,存在多种膜特性类型的神经元 ;致醉剂量的乙醇对大鼠伏隔核神经元的膜特性无明显影响 ,说明乙醇对伏隔核神经元的抑制作用主要并不是通过影响膜特性来实现的。     

离体成年非洲爪蟾视顶盖区突触后电流的研究

用盲法对成年非洲爪蟾视顶盖区的自发微突触后电流（mRSCs)进行全细胞膜片钳记录,观察至了突触后膜有分别由ＡＭＰＡ受体和ＧＡＢＡ受体介导的微兴奋性突触后电流(mEPSCs)和微抑制性突触后电流（mIPSCs),mIPSＣ的发放频率远高于mEPSC,ＧＡＢＡ受体的阻断剂荷包牡丹碱（bicuculline,BM）却能使mEPSC的振幅增加。可能是由于成年期ＡＭＰＡ受体介导的兴奋性活动受到同处于突触后膜的抑制性ＧＡＢＡ受体的制约。尽管因ＮＭＤＡ受体的效能大大下降而记录不到自发电流中的ＮＭＤＡ成分,但远高于生理浓度的外源性ＮＭＤＡ可以诱发去极化的宏电流,说明突触后膜的确仍有ＮＭＤＡ受体存在。而muscimol则能诱发超极化宏电流,这也表明突触后膜上有ＧＡＢＡ受体存在。估计各种受体的一系列变化,使关键期特有的可塑性随神经系统的成熟逐渐降低。     

硬脑膜炎性刺激对三叉神经节小直径神经元电压门控钾电流的影响

目的通过炎性介质(IM)和降钙素基因相关肽(CGRP)诱发偏头痛反复发作,运用全细胞膜片钳的方法观察大鼠三叉神经节小直径神经元电压门控性钾电流的变化。方法雄性SD大鼠15只,分为空白组(不做任何干预)、生理盐水组和IM+CGRP组(大鼠硬脑膜上埋置PE-10管,连续7 d给予等量生理盐水和IM+CGRP)。用Von Frey毛测定大鼠眶周皮肤机械痛阈。在急性分离的三叉神经节小直径神经元上,通过全细胞膜片钳方法记录延迟外向钾电流(IK)和瞬时外向钾电流(IA)的变化。结果给药7 d后,IM+CGRP组大鼠的眶周机械痛阈明显降低,生理盐水组眶周机械痛阈无明显改变。生理盐水组三叉神经节神经元膜上总钾电流、IK、IA与空白组比较无明显差异;IM+CGRP组三叉神经节神经元膜上总钾电流、IK、IA与空白组和生理盐水组比较明显减小。结论 IM和CGRP诱发偏头痛反复发作模型大鼠的三叉神经节中急性分离神经元的IK和IA明显降低,提示电压门控性钾通道可能参与了外周机械痛阈的降低。     

下丘脑神经元NMDA受体通道特性研究

目的通过对正常和缺氧条件下N-甲基-D-天冬氨酸(NMDA)受体通道特性进行研究,探讨下丘脑神经元缺氧损伤的机理,为临床防治脑缺血/缺氧损伤提供实验依据。方法取材于新生SD大鼠下丘脑视前区/下丘脑前区(PO/AH)神经元,应用膜片钳单通道记录技术对缺氧和非缺氧两种状态下NMDA受体特性进行研究,观察其在缺氧和非缺氧条件下的翻转电位、电流幅度、电导特性的变化。结果神经元缺氧后其通道内向电流幅值由平均(4.501±0.980) pA(n=20,40 mV)上升为(6.000±1.750) pA(n=16,40 mV),优势电导由非缺氧组的(45.693±1.850) pS (n=16)上升为(60.206±1.750) pS(n=10),而翻电位极为接近。结论缺氧是使NMDA受体通道过度激活和Ca2+大量内流的一外因条件。神经元缺氧时,同一钳制电压下其内向电流幅度明显高于对照组,优势电导也有明显上升,可以解释为缺氧引起了神经元Ca2+超载,从而介导了细胞的损伤和死亡。     

Ionic basis of the membrane potential responses of rat dorsal vagal motoneurones to HEPES buffer

The effects of 10 mM HEPES (N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid) buffered artificial cerebrospinal fluid (aCSF) on membrane potential and the action potential were studied in 93 dorsal vagal motoneurones (DVMs) using an in vitro slice preparation of the rat medulla. Changing from bicarbonate/CO₂ aCSF to HEPES aCSF resulted in a depolarisation of 6.0 ± 0.6 V and an increase in input resistance (R_In; N = 61). In the presence of 5 mM 4-AP, HEPES either had little effect (n = 9) or hyperpolarised the membrane (n = 10). Mn²⁺ (3 mM) or Ni²⁺ (200 μm) abolished the hyperpolarisation and its associated increase in R_In. In voltage-clamp studies 5 mM 4-AP eliminated a transient outward current and Ni²⁺ blocked an inactivating inward current. It is concluded that HEPES buffer reduces the contribution of the A current to resting membrane potential and also reduces a Ni²⁺-sensitive transient I_Ca.     

Intrinsic membrane potential oscillations in hippocampal neurons in vitro

Membrane potential oscillations (MPOs) of 2-10 Hz and up to 6 mV were found in almost all stable hippocampal CA1 and CA3 neurons in the in vitro slice preparation. MPOs were prominent for pyramidal cells but less pronounced in putative interneurons. MPOs were activated at threshold depolarizations that evoked a spike and the frequency of the MPOs increased with the level of depolarization. MPOs were distinct from and seemed to regulate spiking, with a spike often riding near the top of a depolarizing MPO wave. Analysis of the periodicity of the oscillations indicate that the period of MPOs did not depend on the afterhyperpolarization (AHP) following a single spike. MPOs persisted in low (0-0.1 mM) Ca2+ medium, with or without Cd2+ (0.2 mM), when synaptic transmission was blocked. Choline-substituted low-Na+ (0-26 mM) medium, 3 microM tetrodotoxin (TTX) or intracellular injection of QX-314 reduced or abolished the fast Na(+)-spike and reduced inward anomalous rectification. About 40% of CA1 neurons had no MPOs after Na+ currents were blocked, suggesting that these MPOs were Na(+)-dependent. In about 60% of the cells, a large depolarization activated Ca(2+)-dependent MPOs and slow spikes. MPOs were not critically affected by extracellular Ba2+ or Cs2+, or by 0.2 mM 4-aminopyridine, with or without 2 mM tetraethylammonium (TEA). However, in 5-10 mM TEA medium, MPOs were mostly replaced by 0.2-3 Hz spontaneous bursts of wide-duration spikes followed by large AHPs. Low Ca2+, Cd2+ medium greatly reduced the spike width but not the spike-bursts. In conclusion, each cycle of an MPO in normal medium probably consists of a depolarization phase mediated by Na+ currents, possibly mixed with Ca2+ currents activated at a higher depolarization. The repolarization/hyperpolarization phase may be mediated by Na+/Ca2+ current inactivation and partly by TEA-sensitive, possibly the delayed rectifier, K+ currents. The presence of prominent intrinsic, low-threshold MPOs in all hippocampal pyramidal neurons suggests that MPOs may play an important role in information processing in the hippocampus.     

Effects of trifluoperazine on synaptically evoked potentials and membrane properties of CA1 pyramidal neurons of rat hippocampus in situ and in vitro

The effects of trifluoperazine (TFP), a phenothiazine antipsychotic, on hippocampal activity were studied in the CA1 subfield, both in situ and in slices. In the extracellular studies in situ and in vitro, both somatic population spikes and dendritic excitatory postsynaptic potentials (EPSP) fields were depressed reversibly by TFP, applied by microiontophoresis or in the bath (50-100 μM). Similar effects were also seen during iontophoretic applications of sphingosine in situ. Like TFP (at micromolar concentrations) sphingosine is a dual Ca²⁺/calmodulin-dependent kinase and protein kinase C (PKC) inhibitor. In intracellular recordings from slices, 50-100 μM TFP induced a slow depolarization and a decrease in input resistance (R_N), probably through a β-aminobutyric acid (GABA)-mediated increase in Cl^? conductance (G_Cl). TFP also reduced the slow afterhyperpolarization (AHP) as well as electrically evoked inhibitory postsynaptic potentials (IPSPs), but EPSPs were augmented in both amplitude and duration. When CA1 neurons were voltage clamped, TFP elicited a corresponding inward current (consistent with depolarization), increased the leak conductance, and enhanced excitatory synaptic currents; whereas inhibitory synaptic currents and high-threshold Ca²⁺ currents were reduced. In conclusion, these effects of TFP–which cannot be readily explained by its potent antidopamine action–are in keeping with other evidence that both Ca²⁺/calmodulin-dependent kinase and PKC can modulate G_Cl-conductance and high-threshold Ca²⁺ -conductance, as well as inhibitory and excitatory postsynaptic currents. © 1993 Wiley-Liss, Inc.     

Voltage-dependent membrane currents of cultured human neurofibromatosis type 2 Schwann cells

Previous experimental observations indicate that inhibition of voltage-dependent K⁺ currents suppresses proliferation of normal Schwann cells. In the present study we tested the opposite relationship, i.e., whether Schwann cells from tumors with abnormally high rates of proliferation would have an increase in membrane K⁺ currents. Whole-cell membrane currents were studied in cultured cells from schwannomas of two neurofibromatosis type 2 (NF2) patients (n = 53), one patient with a sporadic schwannoma (n = 22), and two control subjects (n = 41). Five different types of voltage-dependent membrane currents were found in all of the Schwann cells tested. Membrane depolarization activated outward K⁺ and Cl⁻ currents; quinidine was found to block the K⁺ current (IC₅₀ ≈ 1 μM), and NPPB reduced the Cl⁻ current. Ba²⁺-sensitive inward rectifier K⁺ currents, fast Na⁺ currents, and a transient, inactivating K⁺ current were less frequently observed. On average, NF2 cells were found to have statistically significant higher membrane potential and larger non-inactivating K⁺ outward current as compared to controls. Electrophysiological parameters of Schwann cells from a sporadic schwannoma showed a tendency for larger outward currents; however, the difference did not reach statistical significance. Together the data support the suggestion of a possible link between K⁺ outward current and proliferation of Schwann cells. GLIA 24:313–322, 1998. © 1998 Wiley-Liss, Inc.     

Slow oscillation of membrane currents mediated by glutamatergic inputs of rat somatosensory cortical neurons: in vivo patch-clamp analysis

Using in vivo patch-clamp technique, the slow oscillation of membrane currents was characterized by its synaptic nature, correlation with electroencephalogram (EEG) and responses to different anesthetic agents, in primary somatosensory cortex (SI) neurons in urethane-anesthetized rats. In more than 90% of the SI neurons, the slow oscillation of the inward currents (0.1-2.5 Hz) with the duration of several hundreds of a millisecond was observed at the holding membrane potential of -70 mV. The reversal potential of the inward currents was approximately 0 mV and was suppressed by application of an alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) receptor antagonist. In most cases (> 90%) the inward current was synchronized with positive wave of the surface EEG recorded from ipsilateral and even contralateral cortical regions. The frequency as well as duration of the slow oscillation decreased by a volatile anesthetic agent, isoflurane (1.5-5.0%), and excitatory postsynaptic currents (EPSCs) were almost abolished at the highest concentration. Intraperitoneal injection of pentobarbital (25 mg/kg) also decreased the frequency of the slow oscillation without affecting short EPSCs. When gamma-aminobutyric acid A (GABA(A)) receptors were activated by local microinjection of muscimol (3 x 10(-3) m, 1-10 microL) into the thalamus, the frequency of the slow oscillation markedly decreased, but was not abolished completely. These findings suggest that the slow oscillation of the inward currents is generated by the summation of glutamatergic EPSCs, and affected by isoflurane and pentobarbital differently. In addition, GABAergic system in the thalamus can affect the frequency, but is not essentially implicated in the genesis of the slow oscillation.     

Firing pattern of neurons in the nucleus tractus solitarius: modulation by membrane hyperpolarization

Neurons in the ventral region of the nucleus tractus solitarius (NTS) of guinea pigs were studied using an in vitro brainstem slice preparation. One group of neurons was characterized electrophysiologically by a delay between the onset of a depolarizing stimulus and the first spike. This delay could be as large as 760 ms and was modulated by the membrane potential level preceding the stimulus. The firing rate during the depolarizing stimulus was also modulated by the preceding membrane potential level. A fast transient outward current, similar to A-current in molluscan neurons, appeared to be responsible for the delay in firing while a slower calcium-activated potassium current affected the firing rate. These data suggest that intrinsic membrane properties may play an important role in determining the firing pattern of NTS neurons. In vivo, inhibitory synaptic inputs could modulate the expression of these intrinsic properties during subsequent excitation.     

Effect of agonist concentration on the lifetime of GABA-activated membrane channels in spinal cord neurons

The inhibitory neurotransmitter gamma-aminobutyric acid (GABA) hyperpolarizes spinal neurons by activating bicuculline sensitive GABAA receptors coupled to chloride permeable ionic channels in the cell membrane. Single channel measurements using outside-out membrane patches from cultured mouse spinal neurons showed that there is a large excess of brief openings of these channels, compared to the number predicted from a simple, two-state model of channel function. The cumulative open time distributions for channel openings were well fit by the sum of two exponential terms, a fast component with amplitude Nf and time constant TAUf, and a slow term with amplitude Ns and time constant TAUs. These kinetics could arise if monoliganded GABAA receptors triggered an open state less stable than that induced by the biliganded receptor. A prediction of this hypothesis is that the ratio Nf/Ns should decline in an approximately linear fashion with increasing doses of GABA. This was found to be the case, as Nf/Ns declined by a factor of 4.8 on increasing the GABA dose from 0.5 microM to 5 microM. Application of 1.25 microM GABA produced an intermediate value of Nf/Ns, as predicted. In contrast the parameters TAUf and TAUs were not significantly influenced by GABA concentration. Spontaneous, bicuculline sensitive currents were seen in some patches. These events resembled currents triggered by low doses of exogenous GABA, with regard to the values of Nf/Ns, TAUf and TAUs. These results suggest that the spontaneous currents are triggered by endogenous GABA molecules, present in the culture environment at a concentration of 0.5 microM or less.     

Distribution and intrinsic membrane properties of basal forebrain GABAergic and parvalbumin neurons in the mouse

The basal forebrain (BF) strongly regulates cortical activation, sleep homeostasis, and attention. Many BF neurons involved in these processes are GABAergic, including a subpopulation of projection neurons containing the calcium‐binding protein, parvalbumin (PV). However, technical difficulties in identification have prevented a precise mapping of the distribution of GABAergic and GABA/PV+ neurons in the mouse or a determination of their intrinsic membrane properties. Here we used mice expressing fluorescent proteins in GABAergic (GAD67‐GFP knock‐in mice) or PV+ neurons (PV‐Tomato mice) to study these neurons. Immunohistochemical staining for GABA in GAD67‐GFP mice confirmed that GFP selectively labeled BF GABAergic neurons. GFP+ neurons and fibers were distributed throughout the BF, with the highest density in the magnocellular preoptic area (MCPO). Immunohistochemistry for PV indicated that the majority of PV+ neurons in the BF were large (>20 μm) or medium‐sized (15–20 μm) GFP+ neurons. Most medium and large‐sized BF GFP+ neurons, including those retrogradely labeled from the neocortex, were fast‐firing and spontaneously active in vitro. They exhibited prominent hyperpolarization‐activated inward currents and subthreshold “spikelets,” suggestive of electrical coupling. PV+ neurons recorded in PV‐Tomato mice had similar properties but had significantly narrower action potentials and a higher maximal firing frequency. Another population of smaller GFP+ neurons had properties similar to striatal projection neurons. The fast firing and electrical coupling of BF GABA/PV+ neurons, together with their projections to cortical interneurons and the thalamic reticular nucleus, suggest a strong and synchronous control of the neocortical fast rhythms typical of wakefulness and REM sleep. J. Comp. Neurol., 521:1225–1250, 2013. © 2012 Wiley Periodicals, Inc.     

Automatic control of potential and agonist-induced current across the endplate membrane by drug electrophoresis

Two techniques are described that are designed to elicit long and constant postsynaptic depolarizations or agonist-induced currents by the electrophoretic application of agonists to endplate membranes. In the first technique, which can be described as a “pharmacologic voltage clamp,” the current flowing through the agonist pipette is controlled by the potential across the endplate membrane. Sustained depolarizations of constant amplitude can be obtained in this manner, while the agonist current needed to produce and maintain the response is recorded. The second technique uses a signal proportional to the current flowing across a voltage-clamped endplate membrane to control the delivery of agonist. This allows control of the intensity of the agonist-induced current. The possible application of these techniques in studying receptor desensitization and obtaining samples of post-synaptic current noise for spectral analysis is discussed.     

Effects of ginsenosides on Ca channels and membrane capacitance in rat adrenal chromaffin cells

We investigated the effects of ginseng total saponins (GTS) and five ginsenosides on voltage-dependent Ca²⁺ channels and membrane capacitance using rat adrenal chromaffin cells. In this study, cells were voltage-clamped in a whole-cell recording mode and a perforated patch-clamp technique was used. The inward Ca²⁺ currents (I_Ca) was elicited by depolarization and the change in cell membrane capacitance (ΔC_m) was monitored. The application of GTS (100 μg/ml) induced rapid and reversible inhibition of the Ca²⁺ current by 38.8 ± 3.6% (n = 16). To identify the particular single component that seems to be responsible for Ca²⁺ current inhibition, the effects of five ginsenosides (ginsenoside Rb₁, Rc, Re, Rf, and Rg₁) on the Ca²⁺ current were examined. The inhibitions to the Ca²⁺ current by Rb₁, Rc, Re, Rf, and Rg₁ were 15.3 ± 2.2% (n = 5); 36.9 ± 2.4% (n = 7); 28.1 ± 1.9% (n = 12); 19.0 ± 2.5% (n = 10); and 16.3 ± 1.6% (n = 15), respectively. The order of inhibitory potency (100 μM) was Rc > Re > Rf > Rg₁ > Rb₁. A software based phase detector technique was used to monitor membrane capacitance change (ΔC_m). The application of GTS (100 μg/ml) induced inhibitory effects on ΔC_m by 60.8 ± 9.7% (n = 10). The inhibitions of membrane capacitance by Rb₁, Rc, Re, Rf, and Rg₁ were 35.3 ± 5.5% (n = 7); 41.8 ± 7.0% (n = 8); 40.5 ± 5.9% (n = 9); 51.2 ± 7.6% (n = 9); and 35.9 ± 5.1% (n = 10), respectively. The inhibitory potencies of the ginsenosides on ΔC_m were Rf > Rc > Re > Rg₁ > Rb₁. Therefore, we found that GTS and ginsenosides exerted inhibitory effects on both Ca²⁺ currents and ΔC_m in rat adrenal chromaffin cells. These results suggest that ginseng saponins regulate catecholamine secretion from adrenal chromaffin cells and this regulation could be the cellular basis of antistress effects induced by ginseng.