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...     

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。     

Sciatic nerve conditioned medium depleted of pro-NGF modulates sodium currents and neurite outgrowth in PC12 cells

Excitability and axon/dendrite specification are the most distinctive features in the establishment of neuronal polarization. Conditioned medium from rat sciatic nerve (CM) induced a neuronal-like morphology in PC12 cells. Here we show that CM neuritogenic activity is limited to the induction of dendrites in PC12 cells. However, treatment of these cells with CM in combination with a generic inhibitor for tyrosine kinase receptors (k252a) promoted the enhancement of neurite length, development of axons and induction of sodium currents. On the other hand, specific inhibition of TrkA and p75^NTR receptors in CM-treated cells reduced the neurite length in comparison with cells treated only with CM, although the effect over the induction of sodium currents was continuously observed. These results suggested that CM had some components that, even though are able to start the morphological cell differentiation and produce short neurites (likely acting through TrkA and p75^NTR), can restrain further neurite extension. Depletion of pro-NGF isoforms from CM produced a similar effect as the exerted by k252a, TrkA and p75^NTR receptor inhibitors in CM-treated cells, inducing the elicitation of sodium currents. These results suggested that the effect of CM might be mediated through pro-NGF. The difference between the results obtained with the generic inhibitor for Trk receptors and the specific inhibitors for TrkA and p75^NTR receptors in CM-treated cells, suggested that alternative pathways could be used to regulate neurite elongation, axon specification and sodium currents in PC12 cells. These findings represent important clues to improve the understanding of the initiation of neuronal polarity.     

Modulation of neuronal dynamic range using two different adaptation mechanisms

The capability of neurons to discriminate between intensity of external stimulus is measured by its dynamic range. A larger dynamic range indicates a greater probability of neuronal survival. In this study, the potential roles of adaptation mechanisms (ion currents) in modulating neuronal dynamic range were numerically investigated. Based on the adaptive exponential integrate-and-fire model, which includes two different adaptation mechanisms, i.e. subthreshold and suprathreshold (spike-triggered) adaptation, our results reveal that the two adapta-tion mechanisms exhibit rather different roles in regulating neuronal dynamic range. Specifically, subthreshold adaptation acts as a negative factor that observably decreases the neuronal dynamic range, while suprathreshold adaptation has little influence on the neuronal dynamic range. Moreover, when stochastic noise was introduced into the adaptation mechanisms, the dynamic range was apparently enhanced, re-gardless of what state the neuron was in, e.g. adaptive or non-adaptive. Our model results suggested that the neuronal dynamic range can be differentially modulated by different adaptation mechanisms. Additionally, noise was a non-ignorable factor, which could effectively modulate the neuronal dynamic range.     

Practical model description of peripheral neural excitation in cochlear implant recipients: 3. ECAP during bursts and loudness as function of burst duration

In this, the third paper of the series, the loudness of low-rate bursts of electrical pulses was measured as a function of the burst duration, in subjects implanted with the Nucleus^® 24 cochlear implant system (three with straight and two with Contour™ electrode arrays). In order to help distinguish between the contributions of peripheral and more central effects, the ECAP was recorded to the individual pulses comprising the bursts, using the Neural Response Telemetry™ (NRT™) system. At a pulse rate of 250 pulses/s, the ECAP amplitude did not decrease greatly during the bursts: the mean reduction factor was 0.89. The time-constant for summation of the loudness contributions from the pulses comprising a burst was found to be larger than that associated with normal hearing. In addition, the first pulse of a pulse train was found to contribute much more to the overall loudness than did the subsequent pulses, although a corresponding difference was not observed in the ECAP recordings. These results establish a necessary connection between the essentially single-pulse model, developed in the fourth and fifth papers of the series, and the psychophysical data for pulse bursts, but they also have broader implications.     

孤啡肽对大鼠顶叶皮层神经元延迟整流钾电流的抑制作用

目的研究孤啡肽(orphanin FQ/nociceptin,OFQ/N)对大鼠顶叶皮层神经元延迟整流钾电流(IK)的影响,初步探讨其干扰学习记忆过程的离子机制。方法采用全细胞膜片钳技术,观察OFQ/N对急性分离的大鼠顶叶皮层神经元IK的作用。结果①OFQ/N明显抑制IK,并呈剂量依赖性(P<0.05)。②0.1μmol.L-1OFQ/N使IK的电流-电压(I-V)曲线降低(n=8,P<0.01)。③0.1μmol.L-1OFQ/N使IK激活曲线的半数激活电压(V1/2)和斜率因子(k)分别由给药前的(-43.4±6.1)mV和(11.5±1.1)mV变为给药后的(-19.1±4.6)mV和(17.3±3.2)mV(n=8,P<0.01)。④0.1μmol.L-1OFQ/N使IK失活曲线的半数失活电压(V1/2)和斜率因子(k)分别由给药前的(-68.8±2.6)mV和(16.5±1.7)mV变为给药后的(-76.8±2.8)mV(n=5,P<0.01)和(15.7±3.1)mV(n=5,P>0.05)。结论OFQ/N可抑制大鼠顶叶皮层神经元IK,使IK激活曲线右移,失活曲线左移。     

听觉剥夺延缓大鼠上外橄榄核神经元抑制性突触的发育

目的在出生后2周,大鼠上外橄榄核(LSO)神经元所接受的抑制性神经递质投射从以γ-氨基丁酸(GABA)为主逐渐转变为以甘氨酸为主,探讨听觉剥夺对该转变的影响。方法利用电压固定膜片钳技术,观察生后13~15d听觉剥夺大鼠和正常发育大鼠LSO神经元中GABA和甘氨酸受体电流的构成比率。结果在出生后4~6dLSO神经元,GABA和甘氨酸受体电流成分分别为(65.7±5.3)%和(34.3±5.3)%,出生后13~15d正常发育大鼠为(14.9±5.1)%和(84.1±5.1)%;出生后13~15d听觉剥夺大鼠为(38.7±5.9)%和(61.3±5.9)%。与正常发育组相比,听觉剥夺大鼠LSO神经元接受较多的GABA能投射(P<0.001)和较少的甘氨酸受体电流(P<0.001)。结论听觉剥夺大鼠LSO神经元的抑制性神经递质转换现象出现部分受阻,听觉信号刺激与听觉中枢通路的发育相关。     

Patch-clamp recording of Müller glial cells after cryopreservation

Human and other primate retinal Müller cells display dominating K⁺ currents as well as other membrane conductances that may change in cases of retinal pathology. Because the use of human and primate tissue is limited by reasons of availability, a method for long-term storage of these cells is desirable. We describe a cryopreservation method in which isolated Müller cells are stored in liquid nitrogen. After thawing, the cells can be used for patch-clamp experiments immediately, without culturing. We show that the main electrophysiological properties are not altered by this method and that voltage- and ligand-gated currents can be recorded from cryopreserved cells even after 2-years storage.     

硝普钠对豚鼠单离耳蜗外毛细胞全细胞电流的影响

目的研究并探讨硝普钠(sodium nitroprusside,SNP)对豚鼠耳蜗外毛细胞(outer hair cells,OHC)全细胞电流的影响及其作用机制.方法利用急性分离的OHC和特异性的离子通道阻断剂作为工具药,通过膜片钳电压钳记录技术观察了SNP对豚鼠耳蜗OHC全细胞电流的影响,结果①在以 40mV的指令电压刺激时,10-3mol/L的SNP抑制15.34±6.59%的细胞电流(n=5);②SNP对全细胞电流的抑制作用有电压依赖性,在刺激高于0mV时作用明显,10-2mol/L的SNP在 10mV时抑制率为4.97±1.74%,而在 40mV时的抑制率为33.82±1.61%;③SNP对全细胞电流的抑制呈量效关系,在浓度大于10-3mol/L时,抑制作用逐渐明显,10-1mol/L的SNP时接近达到最大抑制效应;④分离离子电流成分后,SNP仅对Ca2 电流有抑制作用.结论SNP对豚鼠耳蜗外毛细胞的全细胞电流的抑制作用,主要通过抑制细胞外Ca2 的内流,进而影响Ca2 依赖性K 通道而实现.     

Inward current responses to urinary substances in rat vomeronasal sensory neurons

No study has yet demonstrated an inward current in response to pheromonal substances in vomeronasal sensory neurons. Using female rat vomeronasal sensory neurons, we here successfully recorded inward currents in response to urine from various sources. Of the neurons that responded to urine, 77% responded to only one type of urine. Male Wistar urine induced responses preferentially in the apical layer of the sensory epithelium, whilst male Donryu and female Wistar urine induced responses mainly in the basal layer of the epithelium. The amplitude of inward currents induced by application of male Wistar urine was voltage-dependent with average amplitude of -47.1+/-6.2 pA at -74 mV. The average reversal potential for male Wistar urine was -9.3 +/-6.1 mV, which was not apparently different from the reversal potentials for urine from different species. It is likely that the urine-induced inward currents in response to different types of urine are mediated via a similar channel. The simultaneous removal of Na+ and Ca2+ from extracellular solution eliminated the response. The magnitude of the urine-induced inward current in Cl--free external solution was similar to that in normal solution, suggesting that the urine-induced current is cation selective. Removal of external Ca2+ enhanced the amplitude of the urine-induced current and prolonged the response. Application of the constant-field equation indicated a very high permeability coefficient for Ca2+. This study first demonstrated that substances contained in urine elicited inward currents, which induce an excitatory response in vomeronasal sensory neurons, through cation-selective channels.