Preferential potentiation by nitric oxide of spontaneous inhibitory postsynaptic currents in rat supraoptic neurones

Magnocellular neurones in the supraoptic nucleus and paraventricular nucleus express mRNA for nitric oxide synthase (NOS) and the expression becomes more prominent when the release of vasopressin or oxytocin is stimulated. It has also been reported that NO donors inhibit the electrical activity of supraoptic nucleus neurones, but the mechanism involved in the inhibition remains unclear. In the present study, to know whether modulation of synaptic inputs into supraoptic neurones is involved in the inhibitory effect of NO, we measured spontaneous excitatory and inhibitory postsynaptic currents (EPSCs and IPSCs) from rat supraoptic nucleus neurones in slice preparations identified under a microscope using the whole-cell mode of the slice-patch-clamp technique. The NO donor, S-nitroso-N-acetylpenicillamine (SNAP), reversibly increased the frequency of spontaneous IPSCs mediated by GABAA receptors, without affecting the amplitude, indicating that NO potentiated IPSCs via a presynaptic mechanism. The NO scavenger, haemoglobin, suppressed the potentiation of IPSCs by SNAP. On the other hand, SNAP did not cause significant effects on EPSCs mediated by non-NMDA glutamate receptors. The membrane permeable analogue of cGMP, 8-bromo cGMP, caused a significant reduction in the frequency and amplitude of both IPSCs and EPSCs. The results suggest that NO preferentially potentiates the inhibitory synaptic inputs into supraoptic nucleus neurones by acting on GABA terminals in the supraoptic nucleus, possibly via a cGMP-independent mechanism. The potentiation may, at least in part, account for the inhibitory action of NO on the neural activity of supraoptic neurones.     

三七总皂苷抗大鼠心肌肥大的作用及其神经机制

目的　探讨三七总皂苷 (PNS)抗腹主动脉缩窄大鼠压力超负荷性心肌肥大的神经机制。方法　①用腹主动脉缩窄法建立心肌肥大模型 ,将大鼠分为假手术对照组、腹主动脉缩窄组及低、中、高剂量组 ,3个剂量组分别每日腹腔注射5 0、10 0和 15 0mgPNS·kg-1。 3wk后处死大鼠检测全心重量/体重 (HW/BW )、左室重量指数 (LVI) ,左心室组织切片HE染色后测心肌纤维直径 (MD)。②细胞内生物电记录技术观察PNS对大鼠星状神经节 (SG)的快兴奋性突触后电位 (f EPSP)、膜电位、膜电阻及对外源性乙酰胆碱引起的膜除极化反应的影响。结果　①高剂量组的HW /BW、LVI及MD显著低于缩窄组 ,P <0 0 1;中剂量组与缩窄组比较MD显著降低 ,P <0 0 5 ;低剂量组与缩窄组比较 ,HW/BW ,LVI和MD三项指标均无显著的变化。②PNS在 0 10～ 0 16g·L-1浓度范围内可使大鼠星状神经节f EPSP可逆性减小 ,PNS还可拮抗高钙对f EPSP的易化作用 ,但对膜电位、膜电阻及外源性ACh引起的膜除极反应无显著的影响。结论　PNS对f EPSP的抑制可能是其抗压力超负荷性心肌肥大的神经机制 ,而抑制作用则是通过突触前机制产生 ,且与拮抗Ca2 + 内流有关。     

Excitatory amino acid levels in cerebrospinal fluid of patients with infantile spasms

Infantile spasm is an age-specific epileptic encephalopathy. Long-term intellectual outcome of affected infants remains poor. The pathogenesis of infantile spasms, as well as the development of mental retardation, remains unclear. Increased excitatory amino acid neurotransmission may play a role in neuronal dysfunction and epilepsy. To study the significance of cerebrospinal fluid excitatory amino acids in infantile spasms, we determined glutamate and aspartate concentrations in cerebrospinal fluid of 13 patients with infantile spasms and 13 controls. The aspartate level in cerebrospinal fluid of the patients with infantile spasms (968 ± 416 nmol/1) was higher than the control group (426 ± 272nmol/l). No difference in the mean glutamate levels was found between the patients (966 ± 395 nmol/1) and the controls (1135 ± 594 nmol/1). The elevated aspartate levels in cerebrospinal fluid of the patients with infantile spasms might be secondary to change in metabolism of aspartate. Aspartate is an excitatory and neurotoxic neurotransmitter, which might have a role in triggering the spasms and the development of neuronal dysfunctions in the patients with infantile spasms.     

兴奋性氨基酸与青光眼

近年来随着对青光眼性视神经病变机制的深入研究,已证实兴奋性氨基酸与青光眼视网膜神经节细胞凋亡密切相关。21世纪青光眼的治疗模式正从传统的单纯降眼压向降眼压的同时从其他途径进一步加强神经保护转变,基础实验及部分临床研究证实干扰兴奋性氨基酸产生神经毒性的各环节均对神经元有保护作用,由此可以推测通过对兴奋性氨基酸的研究有望实现青光眼治疗史上的重大突破。     

灯盏细辛对NMDA所致的大鼠视网膜神经元损伤的保护作用

目的:探讨灯盏细辛(EBHM)是否对N-甲基-D天门冬氨酸(NMDA)导致的大鼠视网膜神经节细胞层(RGCL)神经元兴奋毒性损伤有保护作用。方法:60只健康SD大鼠随机分为4组,其中6只为正常对照组(A组),其余54只随机分为3组,分别为B组(EBHM组),C组(生理盐水加NMDA组),D组(EBHM加NMDA组),每组各18只大鼠。C、D两组大鼠右眼玻璃体内注射NMDA 10 nmol/2 μl制成视网膜损伤模型,左眼玻璃体内注射相同剂量PBS液作为自身对照。B组及D组均在NMDA注射前7d起按15 mg·100 g-1·d-1剂量予6％EBHM腹腔内注射,C组予生理盐水0.5 ml腹腔内注射。在NMDA处理后4,7和14 d处死动物剥取视网膜作全层铺片行RGCL神经元计数分析。结果:正常对照组双眼RGCL神经元计数比较差异无显著性意义(P=0.200)。NMDA干预后4、7 d和14 dEBHM组RGCL神经元计数,双眼与正常对照组比较差异无显著性意义(P>0.05)。生理盐水加NMDA及EBHM加NMDA组实验眼在以上各时段RGCL神经元计数与正常比较差异均有非常显著性意义(P<0.001),左眼与正常对照组比较差异无显著性意义(P>0.05)。实验眼14 d时RGCL神经元计数EBHM加NMDA组高于生理盐水加NMDA组,两者比较差异有显著性(P=0.044),但仍低于正常对照组(P<0.05)。结论:单独使用EBHM对正常大鼠RGCL神经元计数无影响,EBHM可对N     

小型猪颞下颌关节腔内压的测定与分析

 【目的】测量小型猪颞下颌关节上腔内压在下颌3个功能位的变化规律。【方法】用关节内压力测量仪对11只健康成年雌性小型猪在休息位、被动大开口位、被动闭口位的22侧颞下颌关节测量关节内压值。【结果】小型猪左右侧颞下颌关节腔内压值差异无统计学意义（P〉0．05）；休息位压力为（-0．36±0．32）kPa．被动大开口位为（2．02±1．01）kPa，被动闭口位为（0．42±0．36）kPa，3个功能位压力值差异有统计学意义（P〈0．05）。【结论】小型猪两侧颞下颌关节腔内压无显著差异；在休息位，颞下颌关节上腔内压力为负值，被动大开口时压力迅速升高为较大的正压，被动闭口时压力升高为较小的正压。小型猪颞下颌关节无关节后结节，在开口运动中盘后组织跟随盘突运动是被动开口位压力升高为正值的重要解剖生理基础。     

竹节人参对脑缺血大鼠兴奋性氨基酸的影响

目的:探讨富硒竹节人参对大鼠脑缺血及其再灌注后脑组织兴奋性氨基酸(EAA)含量的影响.方法:将大鼠用富硒竹节人参处理后,建立大鼠脑缺血模型,观察富硒竹节人参对大鼠脑组织中的谷氨酸(Glu)、天冬氨酸(Asp)、γ-氨基丁酸(GABA)、甘氨酸(Gly)的影响.结果:富硒竹节人参对正常大鼠脑组织EAA含量无影响,可使脑缺血及其再灌注损伤大鼠脑组织Glu、Asp含量降低,对GABA、Gly无明显影响.结论:富硒竹节人参可对抗缺血性脑损伤,防止缺血时EAA的升高,从而发挥对脑损伤的保护作用.     

A low‐cost,mechanically simple apparatus for measuring eddy current‐induced magnetic fields in MRI

The fidelity of gradient waveforms in MRI pulse sequences is essential to the acquisition of images and spectra with minimal distortion artefacts. Gradient waveforms can become nonideal when eddy currents are created in nearby conducting structures; however, the resultant magnetic fields can be characterised and compensated for by measuring the spatial and temporal field response following a gradient impulse. This can be accomplished using a grid of radiofrequency (RF) coils. The RF coils must adhere to strict performance requirements: they must achieve a high sensitivity and signal‐to‐noise ratio (SNR), have minimal susceptibility field gradients between the sample and surrounding material interfaces and be highly decoupled from each other. In this study, an apparatus is presented that accomplishes these tasks with a low‐cost, mechanically simple solution. The coil system consists of six transmit/receive RF coils immersed in a high‐molarity saline solution. The sensitivity and SNR following an excitation pulse are sufficiently high to allow accurate phase measurements during free‐induction decays; the intrinsic susceptibility matching of the materials, because of the unique design of the coil system, results in sufficiently narrow spectral line widths (mean of 19 Hz), and adjacent RF coils are highly decoupled (mean S₁₂ of ?47 dB). The temporal and spatial distributions of eddy currents following a gradient pulse are measured to validate the efficacy of the design, and the resultant amplitudes and time constants required for zeroth‐ and first‐order compensation are provided. Copyright © 2013 John Wiley & Sons, Ltd.     

促甲状腺激素释放激素对结肠平滑肌钾电流的影响

目的探讨促甲状腺激素释放激素(TRH)对大鼠结肠平滑肌细胞膜瞬时外向钾电流(Ito)和延迟整流钾电流(Ik)的影响。方法酶解法急性分离单个大鼠结肠平滑肌细胞,运用膜片钳方法检测10、20、50、100μmol/L的TRH对结肠平滑肌细胞膜Ito和Ik的影响。结果 TRH浓度依赖性减少Ito(P<0.05),10、20、50、100μmol/L的TRH可使峰值Ito降低13.4%、28.0%、39.5%、53.4%,但Ik降低不明显(P>0.05)。结论 TRH阻滞大鼠结肠平滑肌细胞的瞬时外向钾电流,但不能降低延迟整流钾电流,TRH可能通过调节细胞的兴奋性对肠道动力产生影响。