氯胺酮对大鼠海马锥体神经元电压门控型钠通道的影响

目的研究氯胺酮对大鼠海马锥体神经元电压门控型钠通道的影响。方法急性分离 Wistar 大鼠(鼠龄两周)的海马锥体神经元,应用全细胞膜片钳技术记录电压门控型钠通道电流(INa), 加用不同浓度(50、100、200、500、1000、2000μmol/L)氯胺酮后,计算INa抑制率及半数抑制浓度(IC50); 选择100μmol/L氯胺酮作INa稳态激活及失活曲线。结果50、100、200、500、1000、2000μmol/L氯胺酮对INa的抑制呈浓度依赖性,IC50为(794±21)μmol/L;100μmol/L氯胺酮使INa稳态激活、失活曲线均向超极化方向移动,激活曲线的半数最大激活电位从(-51．6±O．9)．mV移至(-58．5±0．8)mV(P< 0．05),斜率因子(κ)分别为2．0±1．0、(3．2±0．9)mV(P<0．05);失活曲线的半数最大失活电位从 (-66．8±0．8)mV移至(-79．9±0．5)mV(P<0．05),κ分别为-6．6±0．7、(-7．0±0．4)mV(P> 0．05)。结论氯胺酮对电压门控型钠通道有抑制作用,与其全身麻醉作用有关。     

利多卡因对大鼠海马CA1区锥体神经元L-型Ca2+通道开放功能的影响

目的研究不同浓度利多卡因对大鼠海马CA1区锥体神经元L-型Ca^2＋通道开放功能的影响。方法成年SD大鼠,体重200～250 g,雌雄不拘。麻醉后迅速断头取脑,采用酶加机械分离的方法急性分离海马CA1区锥体神经元。配制利多卡因溶液,终浓度依次为2、4、8、16、32μg/ml。选取活力好的细胞,采用膜片钳细胞贴附模式单通道记录技术,依次记录L-型Ca^2＋通道在不同浓度利多卡因作用下单通道的开放时间,并计算开放概率,共观察和记录7个锥体神经元。结果利多卡因对大鼠海马CA1区锥体神经元L-型Ca^2＋单通道功能的影响呈浓度依赖性：与未加利多卡因比较,2和4μg/ml利多卡因对L-型Ca^2＋单通道的功能无明显影响,8和16μg/ml利多卡因使L-型Ca^2＋单通道开放时间延长,开放概率增加（P〈0.05）;32μg/ml利多卡因使L-型Ca^2＋单通道开放时间缩短,开放概率降低（P〈0.05）。结论2和4μg/ml利多卡因对大鼠海马CA1区锥体神经元L-型Ca^2＋单通道无明显影响;8和16μg/ml时有增强作用;32μg/ml时有抑制作用。     

芬太尼对大鼠海马锥体神经元GABAA受体的作用

目的探讨芬太尼对大鼠海马锥体神经元GABAA受体的作用。方法采用酶-机械法急性分离出生3-10 d SD大鼠的海马锥体神经元,用全细胞膜片钳技术记录锥体神经元GABAA受体介导的Cl-电流(GABA电流,IGABA),不同浓度的GABA和1 μmol/L GABAA受体特异性拮抗剂荷包牡丹碱诱发并确定IGABA;用不同浓度的芬太尼和1．0 μmol/L μ受体特异性拮抗剂CTAP评价芬太尼对30 μmol/L GABA诱发IGABA的影响。结果 GABA诱发内向电流(IGABA),其EC50为23．73μmol/L,荷包牡丹碱阻断IGABA;芬太尼剂量依赖性地抑制IGABA,其EC50为0．011 μmol/L,并缩短IGABA的脱敏感时间常数τdes;CTAP使芬太尼抑制GABA诱发IGABA的EC50升至0．414μmol/L;芬太尼不改变IGABA的翻转电位 ECl-(-3．0mV)。结论芬太尼可抑制大鼠海马锥体神经元GABAA受体的功能。     

异丙酚对海马锥体神经元钠通道电流的抑制作用

目的 研究异丙酚对海马锥体神经元钠通道电流的影响,探讨脑钠通道在异丙酚麻醉中的作用。方法 酶消化法急性分离SD大鼠(10～14 d)海马锥体神经元,全细胞膜片钳技术记录异丙酚和脂肪乳剂对其钠通道电流的影响。结果 在钳制电位-100 mV时,4组浓度(10、30、50、100μmol/L)的异丙酚分别抑制峰钠电流为:14.4％±8.7％、42.9％±8.8％、67.2％±18.1％和85.1％±14.9％,抑制程度与浓度呈正相关(r=0.993,P<0.01),IC50为32.5 μmol/L。与本研究中较高浓度异丙酚组(50和100μmol/L)对应浓度的脂肪乳剂(ILP50组和ILP100组)对峰钠电流无明显影响。结论异丙酚对脑钠通道电流有明显的抑制作用,且呈剂量依赖性,提示脑钠通道的抑制在异丙酚的麻醉中可能起一定作用。     

Top-down dendritic input increases the gain of layer 5 pyramidal neurons

The cerebral cortex is organized so that an important component of feedback input from higher to lower cortical areas arrives at the distal apical tufts of pyramidal neurons. Yet, distal inputs are predicted to have much less impact on firing than proximal inputs. Here we show that even weak asynchronous dendritic input to the distal tuft region can significantly increase the gain of layer 5 pyramidal neurons and thereby the output of columns in the primary somatosensory cortex of the rat. Noisy currents injected in ramps at different dendritic locations showed that the initial slope of the frequency-current (f/I) relationship increases with the distance of the current injection from the soma. The increase was due to the interaction of dendritic depolarization with back-propagating APs which activated dendritic calcium conductances. Gain increases were accompanied by a change of firing mode from isolated spikes to bursting where the timing of bursts coded the presence of coincident somatic and dendritic inputs. We propose that this dendritic gain modulation and the timing of bursts may serve to associate top-down and bottom-up input on different time scales.     

吗啡对大鼠海马锥体神经元L-型Ca2+通道电流的影响

目的观察吗啡对大鼠海马锥体神经元L-型Ca^2＋通道电流的影响。方法成年SD大鼠,体重230～270 g,麻醉后快速断头取脑,急性分离海马锥体神经元,12个海马（椎体神经元）随机分为2组（n=6）,吗啡组应用细胞贴附式膜片钳技术记录依次加入不同浓度吗啡[0（未加吗啡）、10^-8、10^-7、10^-6、10^-5mol/L]后海马锥体神经元L-型Ca^2＋通道电流及电导;纳洛酮组加入10^-5mol/L纳洛酮后30min,再依次加入上述不同浓度吗啡,记录此通道电流及电导。结果与未加吗啡比较,吗啡组10^-6、10^-5mol/L吗啡可抑制海马神经元L-型Ca^2＋通道电流,10^-5 mol/L的抑制作用更明显（P＜0．01）;预先加入纳洛酮可阻断吗啡对该通道电流的抑制作用（P＜0．01）;但L-型Ca^2＋通道电导无变化。结论通过作用于μ片受体,10^-6、10^-5 mol/L吗啡可抑制大鼠海马锥体神经元L-型Ca^2＋通道电流,10^-5mol/L的抑制作用更强。     

Sevoflurane improves electrophysiological recovery of rat hippocampal slice CA1 pyramidal neurons after hypoxia

Sevoflurane is a volatile anesthetic agent that reduces cerebral metabolism and thereby may reduce neuronal damage during energy deprivation. We have examined the effect of sevoflurane on hypoxic neuronal damage in rat hippocampal slices. Slices were subjected to 0%, 2%, or 4% sevoflurane 10 minutes before, during, and 10 minutes after hypoxia. The Schaffer collateral pathway was stimulated every 10 seconds and the evoked population spike recorded in the CA1 pyramidal cell region throughout the experiment. During hypoxia, the postsynaptic evoked response was blocked. The time until the blockade of this response in the 0% sevoflurane group was 158 seconds. Sevoflurane (4%) significantly delayed the loss of the evoked response during hypoxia (242 seconds). The percent recovery of the postsynaptic population spike was calculated by dividing the size of the response 120 minutes after hypoxia by its prehypoxic, presevoflurane amplitude. There was no recovery of the population spike in the 0% sevoflurane group 120 minutes after the end of 5 minutes of hypoxia (6 +/- 6%); there was significantly better recovery after 5 minutes of hypoxia in the sevoflurane (4%) treated group (40 +/- 9%). A lower concentration of sevoflurane (2%) delayed the loss of evoked response during hypoxia (191 seconds), but it did not significantly affect recovery of the population spike after hypoxia (7 +/- 7%). Hypoxia irreversibly damages electrophysiologic activity. A high, but clinically usable, concentration of sevoflurane increases the time during hypoxia until the postsynaptic evoked response is blocked and improves recovery of this response after 5 minutes of hypoxia.     

异丙酚对大鼠海马CA1缺血神经元持续钠电流的影响

目的 探讨异丙酚对大鼠海马CA1缺血神经元持续钠电流的影响。方法 酶消化法急性分离SD大鼠海马CA1锥体细胞,通过低氧和无糖法制备神经元缺血模型,全细胞膜片钳技术记录异丙酚对缺血神经元持续钠电流的影响。结果 神经元缺血5 min后持续钠电流显著增强。异丙酚10μmol/L和100μmol/L均能明显抑制缺血引起的持续钠电流增强(与0μmmol/L组比,P<0.01),此作用为异丙酚100μmol/L较10μmol/L儿更强(P<0.05)。结论 异丙酚能够抑制体外脑缺血时海马神经元持续钠电流,这可能是其产生脑保护作用的机制之一。     

不同浓度褪黑激素对新生大鼠海马锥体神经元电压门控性Ca2+通道的影响

目的 探讨不同浓度褪黑激素对新生大鼠海马锥体神经元电压门控性ca2通道的影响.方法 原代培养新生Wistar大鼠(出生时问<12 h)海马锥体神经元7～12 d.配制褪黑激素溶液,终浓度依次为1 nmol/L、10 nmol/L、100 nmol/L、1 μmol/L、10μmol/L、100μmol/L和1 mmol/L.选择胞体清晰、光晕良好、轴突明显的锥体神经元,采用膜片钳全细胞记录模式观察Ca2+通道的基本电生理特点,记录不同浓度褪黑激素作用下Ca2+电流,分析Ca+2通道动力学特性,并计算Ca2+电流变化率.结果 不同浓度褪黑激素均可快速、可逆性地增强Ca2+电流,10 nmol/L和100 nmol/L褪黑激素使Ca2+电流激活曲线向超极化方向移动,其余浓度褪黑激素对Ca2+电流激活曲线的动力学特性无影响.与100 mol/L褪黑激素比较,其余浓度褪黑激素作用后Ca2+电流变化率降低(P<0.05或0.01);与Iμmol/L褪黑激素比较,10 μmol/L、100μmol/L和1 mmol/L褪黑激素作用后Ca2+电流变化率降低(P<0.05).结论 l nmol/L～1 mmol/L褪黑激素均可增强体外培养的新生大鼠海马锥体神经元Ca2+电流,100 nmol/L褪黑激素作用最强.     

Reciprocal alterations in pre- and postsynaptic inhibitory markers at chandelier cell inputs to pyramidal neurons in schizophrenia

In the prefrontal cortex of subjects with schizophrenia, markers of the synthesis and re-uptake of GABA appear to be selectively altered in a subset of interneurons that includes chandelier cells. Determining the effect of these disturbances in presynaptic GABA markers on inhibitory signaling requires knowledge of the status of GABA(A) receptors at the postsynaptic targets of chandelier cells, the axon initial segments (AIS) of pyramidal neurons. Because the alpha(2) subunit of the GABA(A) receptor is preferentially localized at pyramidal neuron AIS, we quantified alpha(2) subunit immunoreactive AIS in tissue sections containing prefrontal cortex area 46 from 14 matched triads of subjects with schizophrenia, subjects with major depression and control subjects. Systematic, random sampling revealed that the mean number of alpha(2)-labeled AIS per mm(2) in subjects with schizophrenia was significantly (P = 0.007) increased by 113% compared to control subjects and non-significantly increased compared to subjects with major depression. Furthermore, within subjects with schizophrenia, the density of alpha(2)-labeled AIS was negatively correlated (r = -0.49, P = 0.038) with the density of chandelier axon terminals immunoreactive for the GABA membrane transporter. These data suggest that GABA(A) receptors are up-regulated at pyramidal neuron AIS in response to deficient GABA neuro-transmission at chandelier axon terminals in schizophrenia. Thus, disturbances in inhibition at the chandelier neuron-pyramidal neuron synapse may be a critical component of prefrontal cortical dysfunction in schizophrenia.     

Nerve injury induces a tonic bilateral mu-opioid receptor-mediated inhibitory effect on mechanical allodynia in mice

BACKGROUND: Mice lacking the mu-opioid receptor gene have been used to characterize the role of mu-opioid receptors in nociception and the analgesic actions of opioid agonists. In this study, the authors determined the role of mu-opioid receptors in neuropathic pain behaviors and the effectiveness of mu- and kappa-opioid receptor agonists on this behavior in mice. METHODS: The authors studied the behavioral responses of mu-opioid receptor knockout and wild-type mice to thermal and mechanical stimuli before and after neuropathic pain induced by unilateral ligation and section of the L5 spinal nerve. Response to mechanical stimuli was evaluated by determining the frequency of hind paw withdrawal to repetitive stimulation using a series of von Frey monofilaments. Thermal hyperalgesia was assessed by determining the paw withdrawal latencies to radiant heat and frequency of hind paw withdrawal to cooling stimuli. The effects of systemic morphine, the kappa-opioid agonist U50488H, and naloxone on responses to mechanical and thermal stimuli were also studied in spinal nerve-injured mice. RESULTS: After spinal nerve injury, wild-type mice developed increased responsiveness to mechanical, heat, and cooling stimuli ipsilateral to nerve injury. mu-Opioid receptor knockout mice not only had more prominent mechanical allodynia in the nerve-injured paw, but also expressed contralateral allodynia to mechanical stimuli. Hyperalgesia to thermal stimuli was similar between mu-opioid knockout and wild-type animals. Morphine decreased mechanical allodynia dose dependently (3-30 mg/kg subcutaneous) in wild-type mice--an effect that was attenuated in the heterozygous mice and absent in the homozygous mu-opioid knockout mice. The kappa-opioid agonist U50488H (3-10 mg/kg subcutaneous) attenuated mechanical allodynia in wild-type, heterozygous, and homozygous mu-opioid mice. Naloxone in wild-type mice resulted in enhanced ipsilateral and contralateral allodynia to mechanical stimuli that resembled the pain behavior observed in mu-opioid receptor knockout mice. CONCLUSIONS: The authors' observations indicate that (1) unilateral nerve injury induces a bilateral tonic activation of endogenous mu-opioid receptor-mediated inhibition that attenuates mechanical allodynia but not thermal hyperalgesia, (2) both mu- and kappa-opioid agonists attenuate neuropathic pain in mice, and (3) the antihyperalgesic actions of morphine are mediated primarily via mu-opioid receptors.     

不同浓度褪黑激素对新生大鼠海马神经元电压门控性瞬时外向钾电流的影响

目的 探讨不同浓度褪黑激素对新生大鼠海马神经元电压门控性瞬时外向钾电流(I_A)的影响.方法 原代培养新生Wistar大鼠(出生时间<12 h)海马锥体神经元7～12 d.配制褪黑激素溶液,终浓度依次为1 nmol/L、10 nmol/L、100 nmol/L、1 μmol/L、10 μmol/L、100 μmol/L和1 mmol/L,选择胞体清晰、光晕良好、轴突明显的锥体神经元采用膜片钳全细胞记录模式记录I_A的基本电生理特点,记录不同浓度褪黑激素作用下I_A的动力学.结果 与褪黑激素作用前比较,1、10 nmol/L褪黑激素作用后海马锥体神经元I_A幅度升高(P<0.05),其余浓度褪黑激素作用前后海马锥体神经元I_A幅度比较差异无统计学意义(P>0.05);10 nmol/L褪黑激素作用后海马椎体神经元电压门控性瞬时外向钾通道激活曲线的半数激活膜电位及曲线斜率因子与褪黑激素作用前比较差异无统计学意义(P>0.05).结论 生理浓度褪黑激素可增加体外新生大鼠海马椎体神经元I_A.     

Catecholaminergic innervation of pyramidal neurons in the human temporal cortex

In the human neocortex, catecholaminergic connections modulate the excitatory inputs of pyramidal neurons and are involved in higher cognitive functions. Catecholaminergic fibers form a dense network in which it is difficult to distinguish whether or not target specificity exists. In order to shed some light on this issue, we set out to quantify the catecholaminergic innervation of pyramidal cells in different layers of the human temporal cortex (II, IIIa, IIIb, V and VI). For this purpose, pyramidal cells were labeled in human cortical tissue by injecting them with Lucifer Yellow, and then performed immunocytochemistry for the rate limiting catecholamine synthesizing enzyme tyrosine hydroxylase (TH) to visualize catecholaminergic fibers in the same sections. Injected cells were reconstructed in three dimensions and appositions were quantified (n = 1503) in serial confocal microscopy images of each injected cell (n = 71). We found TH-immunoreactive appositions (TH-ir) in all the pyramidal cells analyzed, in both the apical and basal dendritic regions. In general, the density of TH-ir apposition was greater in layers II, V and VI than in layers IIIa and IIIb. Furthermore, TH-ir appositions showed a regular distribution in almost all dendritic compartments of the apical and basal dendritic arbors across all layers. Hence, it appears that all pyramidal neurons in the human neocortex receive catecholaminergic afferents in a rather regular pattern, independent of the layer in which they are located. Since pyramidal cells located in different layers are involved in different intrinsic and extrinsic circuits, these results suggest that catecholaminergic afferents may modify the function of a larger variety of circuits than previously thought. Thus, this aspect of human cortical organization is likely to have important implications in cortical function.     

Aging causes a preferential loss of cholinergic innervation of characterized neocortical pyramidal neurons

Aging is known to markedly affect the number and structural characteristics of both pre- and post-synaptic sites in the cerebral cortex. There is evidence that lamina V pyramidal neurons, and their basilar dendrites in particular, are affected by age-related decline. Furthermore, layer V is the area where the greatest overall age- related losses in the total population of synaptic boutons and of cholinergic boutons are observed. Since both pyramidal neurons and cortical cholinergic input are characteristically compromised in aging, we investigated whether aging altered the pattern of cholinergic boutons in apposition to the soma, proximal and distal basal dendrites of intracellularly labeled lamina V large pyramidal neurons in the parietal cortex of young and aged rats. We observed a significant age-related decrease in the population of both total and cholinergic boutons apposed to proximal and distal dendrites of layer V large pyramidal neurons. However, the age-related decreases of cholinergic presynaptic boutons were higher than those in the total bouton population apposed to the pyramidal neurons. The average decrease in cholinergic boutons in aged rats was 3.7-fold more pronounced than the diminution in the overall number of presynaptic boutons. Our results add important new evidence in support of the concept that the age-related learning and memory deficits are attributable, at least partially, to a decline in the functional integrity of the forebrain cholinergic systems.     

Establishment of a mechanical injury model of rat hippocampal neurons in vitro

Objective： To establish a simple, reproducible, and practical mechanical injury model of hippocampal neurons of Sprague-Dawley rats in vitro. Methods ： Hippocampal neurons isolated from 1-2-day old rats were cultured in vitro. Mild, moderate and severe mechanical injuries were delivered to the neurons by syringe needle tearing, respectively. The control neurons were treated identically with the exception of trauma. Cell damage was assessed by measuring the Propidium Iodide （PI） uptaking at different time points （0.5, 1, 6, 12 and 24 hours） after injury. The concentration of neuron specific enolase was also measured at some time points. Results ： Pathological examination showed that degeneration, degradation and necrosis occurred in the injured cultured neurons. Compared with the control group, the ratio of PI-positive cells in the injured groups increased significantly after 30 minutes of injury （P 〈 0.05）. More severe the damage was, more PI-positive neurons were detected. Compared with the control group, the concentration of neuron specific enolase in the injured culture increased significantly after 1 hour of injury （ P 〈 0.05）. Conclusions： The established model of hippocampal neuron injury in vitro can be repeated easily and can simulate the damage mechanism of traumatic brain injury, which can be used in the future research of traumatic brain injury.     

Gangliosides as modulators of dendritogenesis in normal and storage disease-affected pyramidal neurons

Pyramidal cells initiate the formation of dendritic arbors in a prolific burst of neurite outgrowth during early cortical development. Although morphologically mature pyramidal neurons do not normally sprout additional primary dendrites, the discovery of ectopic dendritogenesis in neuronal storage diseases has revealed that these cells do retain this ability under appropriate stimulation. The capacity for renewal of dendritogenesis has been found to exhibit a species gradient with human > cat, dog, sheep > mouse. A consistent metabolic feature of ectopic dendrite-bearing pyramidal neurons is a heightened intracellular expression of GM2 ganglioside. Elevated expression of this same glycosphingolipid has also been found to correlate with normal dendritogenesis. Immature neurons in developing cat and ferret cortex exhibit high levels of GM2 ganglioside immunoreactivity coincident with normal dendritic sprouting and a similar relationship has now been shown for human cortical development. Ultrastructural studies of all three species revealed GM2 localized to vesicles in a manner consistent with Golgi synthesis and exocytic trafficking to the somatic-dendritic plasmalemma. We propose that GM2 ganglioside functions in glycosphingolipid-enriched microdomains (lipid rafts) in the plasmalemma to promote dendritic initiation through modulation of specific membrane proteins and/or their associated second messenger cascades.     

异丙酚对大鼠海马神经元钾离子通道的影响

目的 采用大鼠海马神经元作为研究对象,研究异丙酚对神经元的瞬间外向钾通道、延迟整流钾通道的影响,以探讨静脉麻醉药作用的可能机制。方法 在急性分离的大鼠海马锥体神经元上,利用全细胞膜片钳技术,记录瞬间外向、延迟整流两种钾离子通道的电流。研究异丙酚对这些通道电流幅度和通道动力学的作用。结果 异丙酚对上述通道电流均具有抑制作用,呈可逆性和浓度依赖性,并对离子通道的激活和失活曲线有一定的影响。异丙酚对瞬间外向钾通道和延迟整流钾通道作用的EC50分别为(71±18)和(37±18)μmol·-1,最大抑制率分别为52％±3％和32％±5％。结论 异丙酚对海马神经元上的瞬间外向钾电流、延迟整流钾电流有不同程度抑制作用。异丙酚对锥体神经元兴奋性的影响,可能与影响记忆功能有关。     

孕酮减轻七氟醚诱导原代海马神经元损伤

目的探究孕酮是否能够减轻七氟醚诱导的原代海马神经元损伤及其可能机制。方法取新生24 h内的SD乳鼠,提取海马神经元培养至第7天后随机分为对照组(C组)、七氟醚组(S组)、孕酮+七氟醚组(P组)和醋酸乌利司他+孕酮+七氟醚组(U组)。C组神经元加入溶剂二甲基亚砜(DMSO)后正常培养;S组加入DMSO后行七氟醚处理;P组加入孕酮1μmol/L预处理1h后行七氟醚处理;U组加入醋酸乌利司他1μmol/L预处理1 h后,余同P组。采用CCK-8法检测神经元细胞活力,采用TUNEL染色检测细胞凋亡率,采用Western blot法测定蛋白激酶B(Akt)和磷酸化蛋白激酶B(p-Akt)蛋白含量,在倒置相差显微镜下观察各组细胞形态改变。结果与C组比较,S组细胞活力明显减弱、细胞凋亡率明显升高、p-Akt蛋白含量和p-Akt/Akt比值明显下降(P0.01);与S组比较,P组细胞活力明显增强、细胞凋亡率明显降低、p-Akt蛋白含量和p-Akt/Akt比值明显升高(P0.01);与P组比较,U组细胞活力明显减弱、细胞凋亡率明显升高、p-Akt蛋白含量和p-Akt/Akt比值明显下降(P0.01)。形态学上,C组细胞形态正常,S组和U组细胞表现出凋亡形态,而P组细胞形态基本正常。结论孕酮可通过孕酮受体上调Akt蛋白磷酸化水平减轻七氟醚诱导的原代海马神经元损伤。