柴胡桂枝汤对离体蟾蜍坐骨神经动作电位的影响

目的:研究柴胡桂枝汤对蟾蜍离体坐骨神经干动作电位传导阻滞作用。方法:观察柴胡桂枝汤对蟾蜍离体坐骨神经复合动作电位的振幅和传导速度的影响。结果:柴胡桂枝汤作用0min、2min、4min、6min、8min、10min后均使坐骨神经干复合动作电位的振幅变小(P0.01),传导速度变慢(P0.01)并最终使坐骨神经动作电位消失。结论:柴胡桂枝汤能阻滞神经动作电位的传导。     

分析探讨神经干复合动作电位

目的：讨论分析蛙神经干动作电位，为电生理实验课教学提供一些创新思路。方法：制备蛙的坐骨神经标本，在原有教学实验设计的基础上，就记录距离。麻药阻滞对神经干复合动作电位的波形、幅度、潜伏期及时程的影响，传导速度的计算方法等问题进行深入分析。结果：增大两记录电极距离，在一定范围内第一相峰值逐渐升高，持续时间延长，第二相峰值逐渐减小，电位持续时间逐渐延长，记录两点间滴加麻药，动作电位的波形第一相峰值逐步加大，第二相逐渐变小，直至消失形成单相动作电位；利用顶点所测速度与起点法测量值不相等。结论：讨论分析该实验结果能更好地使学生理解神经干复合动作电位的原理，牢固掌握基本的电生理知识。     

四数九里香挥发油对离体蟾蜍坐骨神经动作电位的影响

目的:研究四数九里香挥发油对离体蟾蜍坐骨神经动作电位的传导阻滞作用。方法:采用水蒸气蒸馏法提取四数九里香挥发油,观察四数九里香挥发油对离体蟾蜍坐骨神经复合动作电位的振幅和传导速度的影响。结果:四数九里香挥发油使坐骨神经复合动作电位的振幅变小(P0.01),传导速度变慢(P0.01),并最终使坐骨神经动作电位消失。结论:四数九里香挥发油能阻滞神经动作电位的传导。     

蛇床子提取液对离体蟾蜍坐骨神经动作电位的影响

目的:研究蛇床子提取液对蟾蜍离体坐骨神经动作电位传导阻滞作用。方法:观察3种浓度蛇床子提取液(1g·ml-1、0.5g·ml-1、0.2g·ml-1)对蟾蜍离体坐骨神经复合动作电位的振幅和传导速度的影响。结果:3种浓度的蛇床子提取液均可使坐骨神经复合动作电位的振幅变小(P0.01),传导速度变慢(P0.01)并最终使坐骨神经动作电位消失。结论:蛇床子提取液能阻滞神经动作电位的传导。     

利用医院设备创造人体机能实验条件

根据我校实际,利用临床仪器开设人体机能实验是从具体情况出发,完善和改进实验教学的一点努力。现在已开设出如“人正中神经动作电位活动观察”,“神经干动作电位传导速度测定”,“神经干阈值测定”,“肌电活动观察”等部份电生理实验和“人心脏内部活动观察”及与心电,电音同步观察示教等,此外还开设了”时间肺活量测     

芍药甘草汤对蟾蜍坐骨神经动作电位的影响

目的:观察芍药甘草汤对蟾蜍离体坐骨神经动作电位阈刺激、不应期及传导速度的影响,研究其对坐骨神经电生理特性的作用。方法:将制备的蟾蜍坐骨神经干分为阈刺激、不应期、传导速度3组,引导神经干动作电位,分别测其正常时与加药后的阈刺激、不应期、传导速度的变化。结果:芍药甘草汤能够提高蟾蜍离体坐骨神经阈刺激,延长不应期,与对照组比有显著性差异(P<0.01);减慢传导速度,与对照组比有显著性差异(P<0.01)。结论:芍药甘草汤对蟾蜍坐骨神经动作电位的抑制作用与提高阈刺激、延长不应期、减慢传导速度相关。     

五味子水煎液对蟾蜍坐骨神经电生理特性的影响

目的:观察五味子水煎液对蟾蜍离体坐骨神经电生理特性的影响。方法:制备蟾蜍坐骨神经-腓神经标本,并将其分为五组:任氏液对照组、5%、10%、30%、50%不同浓度五味子组,采用BL-420生物记录系统采集标本动作电位的振幅和传导速度,并观察不同浓度五味子水煎液对坐骨神经-腓神经动作电位的振幅和传导速度的影响。结果:5%浓度的五味子水煎液能够增大动作电位的振幅(P0.001),并加快动作电位的传导速度(P0.01),而随着五味子水煎液浓度的增大,10%~50%浓度的五味子水煎液可减小蟾蜍离体坐骨神经-腓神经动作电位的振幅(P0.001)并减慢传导速度(P0.001)。结论:五味子水煎液在较低浓度时可加快蟾蜍离体坐骨神经-腓神经动作电位的传导速度并增大振幅,高浓度时能阻滞动作电位的传导。     

肯尼迪病与肌萎缩侧索硬化的肌电图对比研究

目的:研究肯尼迪病(Kennedy’s disease,KD)的肌电图特点,并对其敏感性进行分析。方法:方法:对7例经基因确诊的KD患者行针极肌电图、神经传导、F波和H反射检测,并与18例年龄相匹配的肌萎缩侧索硬化(Amyotrophic lateral sclerosis,ALS)患者进行对比。结果:KD组感觉神经传导速度异常率、动作电位波幅与ALS组比较差异具有统计学意义(P<0.05),且以腓肠神经动作电位波幅异常率最高(71.43%);两组运动神经复合肌肉动作电位波幅、传导速度、F波出现率及H反射潜伏期差异无统计学意义(P>0.05),但KD组的正中神经、尺神经复合肌肉动作电位、远端潜伏期异常率低于ALS组(P<0.05),而H反射潜伏期异常率高于ALS组(P<0.05)。两组的针极肌电图均表现为广泛的神经源性损害,但KD组出现进行性的神经源性损害比例要低于ALS组。结论:与ALS比较,KD的肌电图以广泛的慢性神经源性损害及神经传导异常为主要表现,且神经传导以感觉神经轴索损害更常见。     

压力对周围神经传导功能影响的实验研究

用雄性SD大白鼠24只,研究了压力对神经传导功能的影响。结果表明:受压后运动神经传导速度与动作电位电压呈正相关:压力与运动神经传导速度和动作电位电压呈负相关,持续压力下,压迫时间与运动神经传导速度和动作电位的电压呈负相关。周围神经虽然有一定的抗挤压能力,但如果在压力26.7KPa下压迫超过一小时或压力超过40KPa均可造成神经传导功能阻滞。     

复合动作电位传播速度分布的复时谱估计方法的仿真研究

复合动作电位传播速度分布（ＰＶＤ）的估计，在神经电生理和病理学的基础研究和临床应用方面都具有重要的意义。但是，目前的方法存在许多问题，很少用于临床实践。本文提出了估计ＰＶＤ的复时谱分析方法，通过参考曲线的超前叠加以及尾部压缩，从很大程度上考虑了组成复合动作电位的单纤维动作电位的时程差异。因此得到了满意的结果，仿真研究表明，这个方法算法简单，结果可靠。但是，对于速度范围很宽的ＰＶＤ，估计误差将会增大     

Cutaneous sensibility and peripheral nerve function in patients with unmedicated essential hypertension

Sensorimotor deficits in patients with essential hypertension may be due to impaired nerve function. Cutaneous sensory thresholds, median nerve sensory and motor conduction velocities, and median nerve sensory action potential amplitudes were assessed in 30 patients with unmedicated essential hypertension and 29 normotensives. Cutaneous sensory thresholds were higher and sensory action potential amplitudes smaller in hypertensives than normotensives whereas sensory and motor nerve conduction velocities did not differ between groups. These data suggest that hypertension may reduce the number of active sensory nerve fibers without affecting myelination. Sensory action potential amplitudes were inversely related to cutaneous sensory thresholds, suggesting that subclinical axonal neuropathy of sensory afferents may help account for perceptual deficits that characterize hypertension.     

The association between nerve conduction velocity and the compound action potential amplitude during ischemic blocking

It is not known in detail how the compound sensory nerve action potential amplitude and conduction velocity are associated in nerve ischemia or in other conditions like carpal tunnel syndrome. Ischemia was produced by inflating a tourniquet around the upper arm in five healthy subjects. When median sensory nerve conduction velocities and action potential amplitudes were recorded from the third digit, they decreased in parallel, thereby resembling the blocking process during wrist flexion in healthy subjects. The area under the action potential decreased earlier with longer distances during the ischemic blocking process. A theoretical model is presented in which the area under the compound nerve action potential is determined by the probability for the single fibre action potential to propagate through the internodal distance. This in turn is associated with the internodal conduction time.     

Multiple-electrode nerve cuffs for low-velocity and velocity-selective neural recording

In the paper, a method using multiple-electrode nerve cuffs is presented that enables electroneurographic signals (ENG) to be recorded selectively by action potential velocity. The theory uses a one-dimensional model of the electrodes in the cuff. Using this model, the transfer function for a single tripole is derived, and it is shown that more than one tripole signal can be recorded from within a cuff. When many tripole signals are available and are temporally aligned by artificial delays and summed, there is a significant increase in the amplitude of the recorded action potential, depending on the cuff length and the action potential velocity, with the greatest gain occurring for low velocities. For example, a cuff was considered that was constrained by surgical considerations to 30 mm between the end electrodes. For action potentials with a velocity of 120 ms⁻¹, it was shown that, as the number of tripoles increased from one, the peak energy spectral density of the recorded output increased by a factor of about 1.6 with three tripoles, whereas, for 20 ms⁻¹, the increase was about 19, with ten tripoles. The time delays and summation act as a velocity-selective filter. With consideration of the energy spectral densities at frequencies where are maximum (to give the best signal-to-noise ratio), the tuning curves are presented for these velocity-selective filters and show that useful velocity resolution is possible using this method. For a 30 mm cuff with nine tripoles, it is demonstrated that it is possible to resolve at least five distinct velocity bands in the range 20–120 ms⁻¹.     

Effect of time-varying magnetic fields on the action potential in lobster giant axon

The possible influence of time-varying magnetic fields on action potential in the lobster giant axon was studied. The axon membrane was excited by galvanic stimulation and the action potential was recorded intracellularly with microelectrodes. During the propagation of the action potential along the axon, alternating or pulsed magnetic fields were applied across the middle part of the axon to study whether or not magnetic fields have any effect on parameters such as conduction velocity and refractory period of the nerve fibre and amplitude, duration and shape of the action potentials. No effect on these parameters was observed under different flux densities and frequencies of the magnetic fields. When simulating the conductive properties of tissue surrounding the nerve with the aid of an external conducting loop with a load resistance, action potentials were generated which made it possible to study the threshold value of the induced eddy current for nerve excitation. Based on the results of the experiment, the influence of magnetic flux density, frequency, conductivity, induced EMF and induced eddy current density is discussed, and a method is proposed for estimating the threshold values of magnetic flux density for nerve excitation.     

Backfiring of the isolated rat phrenic nerve does not collide with impulse propagation following repetitive nerve stimulation at 1–50 Hz

Acetylcholinesterase inhibition with neostigmine in the isolated rat phrenic nerve-hemidiaphragm preparation induced axonal backfiring and repetitive compound muscle action potentials following single nerve stimulation. The duration of backfiring and the repetitive compound muscle action potentials did not exceed 55 ms. With repetitive nerve stimulation at frequencies ranging from 1 to 50 Hz, backfiring was present only with the first stimulus and the amplitude of the second compound muscle action potential was maximally reduced, while the subsequent responses recovered gradually. However, the amplitudes of the concommitant antidromic nerve action potentials remained unchanged during the entire train of stimulation. Lack of nerve action potential amplitude changes and the short duration of backfiring of the first nerve action potential exclude a collision phenomenon of backfiring with the nerve action potential induced by the second stimulus. Moreover, the duration of the repetitive compound muscle action potentials did not exceed the duration of backfiring. Therefore, the prolongation of the muscle membrane refractory period by reexcitation following backfiring cannot explain the decrement of the second compound muscle action potential.     

Bispectral de-noising of the compound action potential for estimation of the nerve conduction velocity distribution

The distribution of the conduction velocities (DCV) of a peripheral nerve is a powerful diagnostic tool for the assessment of neuromuscular disorders. Its efficient calculation depends on the signal-to-noise ratio (SNR) of the acquired electroneurograms (ENGs), thus, time averaging is solely used. An alternative way of improving the SNR is based on averaging in the bispectrum domain and it is proposed in this work. The compound action potential (CAP) is a linear summation of the single fiber action potentials (SFAPs) propagating along the nerve fibers and can be expressed, in the discrete time, as the circular convolution of a delay sequence (DS) and the sampled SFAP. In the proposed method, averaging of low SNR CAP measurements is done in third order spectrum domain so no time alignment is required. Averaged bispectra are introduced in modified Hirose's method, to estimate the delay sequence for a conduction distance l1. The lost linear phase is recovered by using the delay phase cepstrum. Finally, the DCV can be calculated from the estimated DS, according to the formulation of the forward problem. Comparison between time and bispectrum averaging is performed using simulated data, proving the more efficient performance of the proposed method, especially in the case of noisy ENGs.     

Activity-dependent modulation of axonal excitability in unmyelinated peripheral rat nerve fibers by the 5-HT(3) serotonin receptor

Activity-dependent fluctuations in axonal excitability and changes in interspike intervals modify the conduction of trains of action potentials in unmyelinated peripheral nerve fibers. During inflammation of a nerve trunk, long stretches of axons are exposed to inflammatory mediators such as 5-hydroxytryptamine [5-HT]. In the present study, we have tested the effects of m-chlorophenylbiguanide (mCPBG), an agonist at the 5-HT(3) serotonin receptor, on activity- and potential-dependent variations in membrane threshold and conduction velocity of unmyelinated C-fiber axons of isolated rat sural nerve segments. The increase in axonal excitability during application of mCPBG was much stronger at higher frequencies of action potentials and/or during axonal membrane hyperpolarization. The effects on the postspike recovery cycle also depended on the rate of stimulation. At an action potential frequency of 1 Hz or in hyperpolarized axons, mCPBG produced a loss of superexcitability. In contrast, at 0.33 Hz, a small increase in the postspike subexcitability was observed. Similar effects on excitability changes were found when latency instead of threshold was recorded, but only at higher action potential frequencies: at 1.8 Hz, mCPBG increased conduction velocity and reduced postspike supernormality. The latter effect would increase the interspike interval if pairs of action potentials were conducted along several cm in an inflamed nerve trunk. These data indicate that activation of axonal 5-HT(3) receptors not only enhances membrane excitability but also modulates action potential trains in unmyelinated, including nociceptive, nerve fibers at high impulse rates.     

Models and analysis of compound nerve action potentials

Upon electrical stimulation of a peripheral nerve, a compound action potential (CAP) can be recorded, a procedure that is widely used to study the functional condition of a nerve. The CAP provides relevant information about such parameters as the number of active myelinated fibers and their propagation velocities. This paper reviews methods of model-based CAP analysis that have emerged during the last decade. First, the basic model formulation for the CAP as resulting from a linear summation of the underlying single fiber action potentials (SFAPs) is discussed. Subsequently, a survey is given of volume conductor model approaches for the prediction of the SFAPs. Attention is then concentrated on the "inverse" problem of extracting relevant nerve parameters from experimentally recorded CAPs. Finally, the applicability of such methods is discussed and a direction for future developments is outlined.     

High prevalence of carpal tunnel syndrome in children with mucopolysaccharidosis type II (Hunter syndrome)

Although carpal tunnel syndrome (CTS) is the most common compressive neuropathy seen in the upper extremity of adults, it is rarely seen in children. Several reports have shown that mucopolysaccharidosis type II (Hunter syndrome), a rare genetic disorder, is one of the causes of CTS in children. Usual symptoms of CTS are pain, weakness, and paresthesias in the hand and digits. However, the diagnosis of CTS in Hunter syndrome is often delayed or unrecognized because of atypical symptoms and cognitive impairment. Here, we report the prevalence, clinical manifestation, and nerve conduction profiles of CTS in 45 Hunter syndrome patients. The mean age of the study participants was 117.1 (74.9) months (range: 4-408 months); all patients were male. Forty-three (96.0%) of the 45 patients with Hunter syndrome had CTS. Bilateral CTS was observed in all patients; 73 (82.0%) of the patients' hands had severe degree of CTS. Intriguingly, in contrast with other nerve velocities, decreases in forearm conduction velocities of the median nerve were observed in 28 (31.5%) of 89 hands with CTS. There was a significant difference in age (P < 0.001) between hands with normal, mild, moderate, and severe grades of CTS. The compound muscle action potential and sensory nerve action potential amplitudes of the median nerves decreased with age (CMAP, r = -0.526, P < 0.001; SNAP, r = -0.564, P < 0.001). Early recognition and intervention to ameliorate the symptoms of CTS are important in improving the quality of life of Hunter syndrome patients.