基因修饰细胞移植治疗大鼠脊髓损伤的电生理评价

目的：采用神经电生理检查方法,观察逆转录病毒载体介导脑源性神经营养因子（ＢＤＮＦ）基因修饰成肌细胞对损伤脊髓的治疗作用。方法：３０只ＳＤ大鼠在Ｔ９水平制成脊髓横断损伤模型,并随机分为基因细胞组（Ａ组）、成肌细胞组（Ｂ组）及损伤对照组（Ｃ组）,每组１０只大鼠。术后３个月,采用皮质体感诱发电位（ＣＳＥＰ）和运动诱发电位（ＭＥＰ）等电生理检测技术,观察轴突是否有再生及其神经功能恢复程度。结果：（１）Ａ组     

Lasting reduction in mesolimbic dopamine neuronal activity after morphine withdrawal

The activity of mesolimbic dopaminergic neurons was investigated in rats at various times after a chronic regimen of morphine, which produced, upon suspension, a marked somatic withdrawal syndrome. Single-cell extracellular recording techniques, coupled with antidromic identification from the nucleus accumbens, were used to monitor neuronal activity while behavioural observations allowed quantification of the somatic signs of morphine withdrawal. Temporal correlation of electrophysiological indices, such as firing rate and burst firing, with scores obtained through behavioural assessments proved negative, in that somatic signs were pronounced at 24 h after suspension of treatment and then subsided to control values at 72 h after the last morphine injection. In contrast, the firing rate and burst firing of mesolimbic dopaminergic neurons were found to be reduced at 1, 3 and 7 days after morphine withdrawal. After 14 drug-free days, electrophysiological analysis revealed an apparent normalization of various parameters. However, at this time, intravenous administration of morphine produced an increment of electrical activity which was significantly higher than that obtained in control (saline treated) rats. Further, administration of the opiate antagonist naltrexone, administered without prior morphine, at 3, 7 and 14 days after the last morphine administration, failed to alter dopaminergic neuronal activity. The results indicate: (i) that the activity of mesolimbic dopaminergic neurons remains reduced well after somatic signs of withdrawal have disappeared; (ii) after 14 days of withdrawal, the augmented magnitude of the electrophysiological response to exogenous morphine suggests an increased sensitivity of opiate receptors; and (iii) the lack of relationship between dopaminergic activity and somatic signs of withdrawal corroborates the notion that dopaminergic activity in the mesolimbic system does not participate in the neurobiological mechanisms responsible for somatic withdrawal. The present results may be relevant to the phenomenon of drug addiction in humans and consequent relapse after drug-free periods.     

Perirhinal cortex input to the hippocampus in the rat: evidence for parallel pathways, both direct and indirect. A combined physiological and anatomical study

The possibility of a direct projection from the perirhinal cortex (PER) to areas CA1 and subiculum (SUB) in the hippocampus has been suggested on the basis of tracer studies, but this projection has not unequivocally been supported by physiological studies. The demonstration of such a functional pathway might be important to understand the functioning of the hippocampal memory system. Here we present physiological and further anatomical evidence for such a connection between PER and the hippocampus. Electrical stimulation of PER in vivo evoked field potentials (EFPs) at the border area of CA1/SUB, consisting of a short latency and a longer latency component. Current source density analysis revealed that the sink of the short latency component was situated in the molecular layer of area CA1/SUB, while the longer latency component had its sink in the outer molecular layer of the dentate gyrus (DG). Anterograde tracer injections in PER showed labelled fibres in the border area of CA1/SUB, but anatomical evidence for a projection of PER to DG was not found. When synaptic transmission in the entorhinal cortex was partly blocked, the amplitude of the longer latency component of the recorded EFPs in the hippocampus was decreased while the short latency component was not affected, which suggests that the indirect pathway originating in PER is mediated through a synaptic relay in the entorhinal cortex. From the present results we conclude that information originating in PER reaches area CA1/SUB by parallel, direct and indirect, routes. The existence of this parallel organization appears to form an essential feature for the proper function of the medial temporal lobe memory system.     

Sodium channel blockade enhances dispersion of the cardiac action potential duration

Summary The goal of this study was to elucidate the causes why the proarrhythmic activity of sodium channel blocking drugs is enhanced during the post-infarction period. Therefore, we studied the effects of a reduction in sodium conductance on the action potential duration and its dispersion in a simulated array of 1600 ventricular myocytes. Cardiac tissue is known to possess anisotropic properties with regard to the intercellular electrical resistance (R). Infarction as well as aging causes deposition of collagen in the cardiac tissue, thereby inducing zones of high electrical resistance leading to a non-uniform anisotropy (Spach et al., Circ Res 62811, 1988). For our study an array of 40*40 ventricular myocytes was simulated using Beeler-Reuter-algorithms. Physical tissue properties were assumed to be either a) uniform anisotropic (i.e., all longitudinal R=5000 cm, all transversal R=20000 cm; UA) or b) non-uniform anisotropic (i.e., transversal R for the inner 10*10 cells was set to 10¹⁰ cm; NUA). Mean action potential duration (APD) was increased under UA (287 ms, dispersion: 0,8 ms) when compared to NUA (285 ms, disp.: 3,2 ms). Assuming a 25% decrease in sodium conductance, we found the total activation time (TAT) to be increased (from 99 to 139 ms), indicating slowing of conduction, APD to be shortened (from 287 to 259 ms), and the APD-dispersion to be increased (from 0.8 to 29 ms) in UA. These changes were more pronounced in the case of NUA: increase in TAT from 103 to 150 ms, APD-shortening from 285 to 214 ms and a marked increase in APD-Dispersion from 3.2 to 53 ms). From these results it is concluded that a) the effects of a reduced sodium conductance are more pronounced in NUA tissue, and b) that the resulting increase in dispersion may provoke arrhythmia by local differences in APD.This may be one of the mechanisms underlying the increased proarrhythmic risk of class I antiarrhythmic drugs in the postinfarction period.     

Electrophysiological profile of bepridil, a new anti-anginal drug with calcium blocking properties

The electrophysiological effects of intravenously administeredbepridil, a new anti-anginal drug with slow calcium currentblocking properties, were studied in 20 patients undergoingan endocavitary cardiac exploration for various reasons. Classicaltechniques of programmed electrical stimulation were used. Bepridilmarkedly increased the refractory period of the atrium, atrioventricularnode and the AH- interval. The effects on HR and ventricularrefractory period were minimal, and sinus rate decreased slightly.A pronounced reduction in the heart rate at which the Wenckebachphenomenon was obtained in the anterograde direction (16%) andparticularly in the retrograde direction (26%) was observed. During this study the drug appeared beneficial in suppressingatrial flutter, atrial extrasystoles, and ventricular extrasystoles.In two patients with intranodal reciprocal rhythm, the injectionof bepridil terminated the tachycardia which could not be reinitiatedlater. No side-effects occurred and it appears that bundle branchblock and prolonged HV interval are not contraindications tothe use of bepridil.     

Binocular Interactions in the Lateral Suprasylvian Visual Area of Strabismic Cats Following Section of the Corpus Callosum

Visually responsive neurons have been recorded in the lateral suprasylvian area (LSA) of cats raised with either a convergent or a divergent strabismus. In contrast to areas 17 and 18, where many studies have documented a profound loss of binocularly activated neurons following early strabismus, in the LSA the majority of cells could still be binocularly driven. Acute or chronic section of the splenium of the corpus callosum reduced but did not abolish binocularity in the LSA. We propose that the widespread callosal connections, the large size of the receptive fields and the peculiar internal circuitry of the LSA all concur in permitting the maintenance of binocular coding in spite of early misalignment of the eyes.     

Evolution of changes in neuronal activity in the subthalamic nucleus of rats with unilateral lesion of the substantia nigra assessed by metabolic and electrophysiological measurements

Cellular expression of cytochrome oxidase subunit I (COI) mRNA has recently been used as a metabolic marker for neuronal activity to study the functional changes in the subthalamic nucleus (STN) in parkinsonism. The previous experimental studies have been performed when the pathological state was stabilized at a maximal level. In order to determine the evolution of changes in neuronal activity in the STN after nigrostriatal denervation, we analysed by in situ hybridization the cellular expression of COI mRNA in the subthalamic neurons at different times, from 6 h to 14 days, after unilateral intranigral microinjection of 6-hydroxydopamine (6-OHDA) in rats. In parallel, the time-dependent changes of the unit neuronal activity of subthalamic neurons have been recorded. Levels of COI mRNA increased by 41% in subthalamic neurons from 24 h after 6-OHDA intoxication, to 14 days (+26%). Similarly, electrical activity started to increase slightly 24 h after lesion (+20%) and remained significantly higher at 14 days after the lesion (+189%). Changes in neuronal mean discharge rate were associated with changes in the pattern of spiking activity, from a regular firing pattern to an irregular one with a high bursting activity. These results show that: (i) the hyperactivity of the STN represents a very early phenomenon in the physiopathology of parkinsonian syndromes; and (ii) that changes in COI mRNA expression slightly precede changes in electrical neuronal activity.     

A novel conotoxin inhibiting vertebrate voltage-sensitive potassium channels.

Toxins from cone snail (Conus species) venoms are multiple disulfide bonded peptides. Based on their pharmacological target (ion channels, receptors) and their disulfide pattern, they have been classified into several toxin families and superfamilies. Here, we report a new conotoxin, which is the first member of a structurally new superfamily of Conus peptides and the first conotoxin affecting vertebrate K+ channels. The new toxin, designated conotoxin ViTx, has been isolated from the venom of Conus virgo and comprises a single chain of 35 amino acids cross-linked by four disulfide bridges. Its amino acid sequence (SRCFPPGIYCTSYLPCCWGICCSTCRNVCHLRIGK) was partially determined by Edman degradation and deduced from the nucleotide sequence of the toxin cDNA. Nucleic acid sequencing also revealed a prepropeptide comprising 67 amino acid residues and demonstrated a posttranslational modification of the protein by releasing a six-residue peptide from the C-terminal. Voltage clamp studies on various ion channels indicated that the toxin inhibits the vertebrate K+ channels Kv1.1 and Kv1.3 but not Kv1.2. The chemically synthesized product exhibited the same physiological activity and identical molecular mass (3933.7 Da) as the native toxin.     

QT and RR intervals in conscious and anesthetized guinea pigs with highly varying RR intervals and given QTc-lengthening test articles.

A facile system for obtaining electrocardiograms from conscious animals was used to conduct studies on 12 animals studied both conscious and anesthetized, on 4 conscious animals given vehicle (0.5% methylcellulose) and QT-lengthening test articles, and on 6 animals given test articles thought to not lengthen QTc. In 12 animals whose ECGs were monitored via a bipolar transthoracic ECG, heart rates were slowed with 1.0 mg/kg zatebradine, while they were conscious in their slings, and after being anesthetized with ketamine/xylazine. The following regression equations were obtained relating QT to RR: QT = 44.7 ln RR - 132.9, r2 = 0.7, for conscious animals; QT = 79.4 ln RR - 287.4, r2 = 0.8 for anesthetized animals, with RR intervals varying between 150 and 550 ms. The anesthetic increases QT at all RR intervals (p < 0.001), but does not change the slope of the relationship between QT and RR when compared with the conscious guinea pig. The Fridericia method was best for correcting QT for RR interval in conscious guinea pigs, but the Bazett method was best for correcting in anesthetized animals. QTc lengthened significantly in all conscious guinea pigs given, orally, cisapride, ketoconazole, and sotalol (positive test articles) and did not change with methylcellulose (the vehicle) or with propranolol, verapamil, or enalapril (negative controls). These techniques and relationships demonstrate that this methodology may be useful in exploring torsadogenic effects of novel pharmacological entities.     

氯丙烯中毒大鼠神经电生理时间效应关系

目的探讨氯丙烯亚慢性中毒大鼠坐骨神经的电生理指标改变时间效应关系。方法选用Wistar雄性大鼠,以200 mg/(kg.bw)剂量经口灌胃,每周3次,在第0,3,6,9,12周,用电生理仪分别测定相应对照组与染毒组大鼠坐骨神经传导速度、复合动作电位峰峰值、潜伏期、时程、阈强度及最大刺激强度等指标。结果电生理各指标变化随时间和步态评分呈进行性加重,坐骨神经传导速度从第6周和步态评分2分开始降低,与对照组相比差异有统计学意义(P<0.05);复合动作电位峰峰值从第12周和步态评分4分开始降低,与对照组相比差异有统计学意义(P<0.05);,其它各指标均从第9周和步态评分3分开始逐渐增大,与对照组相比差异亦有统计学意义(P<0.05)。结论氯丙烯引起的坐骨神经电生理各指标的改变存在时间效应关系,其中以传导速度改变的最早、最为敏感,为氯丙烯中毒的早期诊断提供一定的依据。