二苯乙烯苷和远志总皂苷配伍对Aβ25-35诱导PC12细胞损伤的影响

目的探讨二苯乙烯苷(tetrahydroxy stilbene glycoside,TSG)和远志总皂苷(Tenuigenin,TEN)配伍对Aβ25-35诱导的PC12细胞损伤的影响。方法PC12细胞除空白组外运用Aβ25-35诱导建立阿尔茨海默病(Alzheimer’s disease,AD)模型,被随机分成模型组、TSG(200 mmol/L)组、TEN组(100 mg/L)、TSG-TEN配伍组(TSG200 mmol/L+TEN100 mg/L)、多奈哌齐组(10μmol/L)。采用MTT比色法检测各组细胞存活率;取细胞上清液分别测各组的乳酸脱氢酶(LDH)、丙二醛(MDA)含量及乙酰胆碱酯酶(AchE)、超氧化物歧化酶(SOD)活力;统计各组的细胞分化率。结果(1)细胞存活率的高低为:TSG-TEN组>TSG组>多奈哌齐组>TEN组(P<0.01);TSG组、TEN组、多奈哌齐组均低于TSG-TEN配伍组(P<0.01,P<0.05);(2)与模型组比较,TSG组、TEN组、TSG-TEN配伍组可降低LDH含量、MDA含量、抑制AchE活力及增强SOD活力(P<0.05)。且TSG-TEN配伍组对降低LDH含量、MDA含量、抑制AchE活力及增强SOD活力效应比TSG或TEN单用组效应更好(P<0.01);(3)PC12细胞的分化率高低为:TSG-TEN组>多奈哌齐组>TSG组>TEN组(P<0.01,P<0.05);TSG组、TEN组、多奈哌齐组均低于TSG-TEN配伍组(P<0.01,P<0.05)。结论TSG和TEN配伍对Aβ25-35诱导的PC12细胞损伤具有显著的协同保护作用,其作用机制可能与改善胆碱能系统、抗氧化应激、降低突触可塑性损伤有关,且TSG优于TEN。     

肉苁蓉总苷对阿尔茨海默病模型大鼠学习认知功能和氧化应激的影响*

目的：探讨肉苁蓉总苷（ GCs）对阿尔茨海默病（AD）模型大鼠学习认知功能的影响及其作用机制。方法： 双侧脑室注射Aβ1-42 制备AD大鼠模型,连续给予模型大鼠不同剂量的GCs 腹腔注射20 d,Morris 水迷宫检测各 组大鼠空间学习记忆能力,尼氏染色观察海马CA1区细胞形态并计数正常锥体细胞;免疫组织化学测定脑组织突 触素（ SYN）含量、酶联免疫吸附试验测定血清超氧化物歧化酶（ SOD）和谷胱甘肽过氧化物酶（ GSH-Px）活 性、丙二醛（ MDA）的含量。结果：GCs 可明显缩短逃避潜伏期与上台前路程,明显增加目标象限时间百分比 与穿越平台次数;GCs 能提高海马CA1区锥体细胞的存活率,明显增加SYN蛋白的表达和提高SOD、GSH-Px 活 性,降低MDA的活性。结论：GCs 改善AD学习认知障碍的机制可能是通过减少自由基堆积、清除体内过多的 过氧化物,进而提高突触可塑性来改善学习认知功能。     

Cellular plasticity: A mechanism for homeostasis in the kidney

Cellular plasticity is a topical subject with interest spanning a wide range of fields from developmental biology to regenerative medicine. Even the nomenclature is a subject of debate, and the underlying mechanisms are still under investigation. On top of injury repair, cell plasticity is a constant physiological process in adult organisms and tissues, in response to homeostatic challenges. In this review we discuss two examples of plasticity for the maintenance of homeostasis in the renal system—namely the renin‐producing juxtaglomerular cells (JG cells) and cortical collecting duct (CCD) cells. JG cells show plasticity through recruitment mechanisms, answering the demand for an increase in renin production. In the CCD, cells appear to have the ability to transdifferentiate between principal and intercalated cells to help maintain the highly regulated solute transport levels of that segment. These two cases highlight the complexity of plasticity processes and the role they can play in the kidney.     

大鼠脑梗死后突触素的变化及针刺的影响

目的　观察大鼠脑梗死及电针干预后突触素 (SYP)的动态变化 ,探讨突触可塑性的物质基础、机制及针刺的影响。方法　通过建立大鼠局灶性脑缺血模型 (MCAO)〔1〕,用免疫组化的方法 ,测定梗死对照组 (A组 )、针刺干预组 (B组 )、正常对照组 (C组 ) ,在 6h、2 4 h、3d、7d不同时间点 SYP的动态变化。结果　梗死灶中心区无明显 SYP阳性染色。A组 :梗死灶周围皮质阳性表达率于 6h、2 4 h表达减少 ,3d达最低值 ,7d开始增高但不及正常表达数值。病灶对侧对应区从 6 h始表达增加 ;B组 :针刺后阳性表达率增加。 A组和 B组比较有明显差异 ;C组无变化。结论　 MCAO大鼠梗死灶周围皮层 SYP变化明显 ,对侧对应皮层表达亦增加 ,表明存在明显的突触可塑性变化 ,针刺可促进这种可塑性变化 ,可能是主要的脑功能恢复的物质基础。     

Rab3B protein is required for long-term depression of hippocampal inhibitory synapses and for normal reversal learning

Rab3B, similar to other Rab3 isoforms, is a synaptic vesicle protein that interacts with the Rab3-interacting molecule (RIM) isoforms RIM1α and RIM2α as effector proteins in a GTP-dependent manner. Previous studies showed that at excitatory synapses, Rab3A and RIM1α are essential for presynaptically expressed long-term potentiation (LTP), whereas at inhibitory synapses RIM1α is required for endocannabinoid-dependent long-term depression (referred to as "i-LTD"). However, it remained unknown whether i-LTD also involves a Rab3 isoform and whether i-LTD, similar to other forms of long-term plasticity, is important for learning and memory. Here we show that Rab3B is highly enriched in inhibitory synapses in the CA1 region of the hippocampus. Using electrophysiological recordings in acute slices, we demonstrate that knockout (KO) of Rab3B does not alter the strength or short-term plasticity of excitatory or inhibitory synapses but does impair i-LTD significantly without changing classical NMDA receptor-dependent LTP. Behaviorally, we found that Rab3B KO mice exhibit no detectable changes in all basic parameters tested, including the initial phase of learning and memory. However, Rab3B KO mice did display a selective enhancement in reversal learning, as measured using Morris water-maze and fear-conditioning assays. Our data support the notion that presynaptic forms of long-term plasticity at excitatory and inhibitory synapses generally are mediated by a common Rab3/RIM-dependent pathway, with various types of synapses using distinct Rab3 isoforms. Moreover, our results suggest that i-LTD contributes to learning and memory, presumably by stabilizing circuits established in previous learning processes.     

Wnt7a signaling promotes dendritic spine growth and synaptic strength through Ca²⁺/Calmodulin-dependent protein kinase II

The balance between excitatory and inhibitory synapses is crucial for normal brain function. Wnt proteins stimulate synapse formation by increasing synaptic assembly. However, it is unclear whether Wnt signaling differentially regulates the formation of excitatory and inhibitory synapses. Here, we demonstrate that Wnt7a preferentially stimulates excitatory synapse formation and function. In hippocampal neurons, Wnt7a increases the number of excitatory synapses, whereas inhibitory synapses are unaffected. Wnt7a or postsynaptic expression of Dishevelled-1 (Dvl1), a core Wnt signaling component, increases the frequency and amplitude of miniature excitatory postsynaptic currents (mEPSCs), but not miniature inhibitory postsynaptic currents (mIPSCs). Wnt7a increases the density and maturity of dendritic spines, whereas Wnt7a-Dvl1-deficient mice exhibit defects in spine morphogenesis and mossy fiber-CA3 synaptic transmission in the hippocampus. Using a postsynaptic reporter for Ca(2+)/Calmodulin-dependent protein kinase II (CaMKII) activity, we demonstrate that Wnt7a rapidly activates CaMKII in spines. Importantly, CaMKII inhibition abolishes the effects of Wnt7a on spine growth and excitatory synaptic strength. These data indicate that Wnt7a signaling is critical to regulate spine growth and synaptic strength through the local activation of CaMKII at dendritic spines. Therefore, aberrant Wnt7a signaling may contribute to neurological disorders in which excitatory signaling is disrupted.     

Na+-mediated coupling between AMPA receptors and KNa channels shapes synaptic transmission

Na⁺-activated K⁺ (K_Na) channels are expressed in neurons and are activated by Na⁺ influx through voltage-dependent channels or ionotropic receptors, yet their function remains unclear. Here we show that K_Na channels are associated with AMPA receptors and that their activation depresses synaptic responses. Synaptic activation of K_Na channels by Na⁺ transients via AMPA receptors shapes the decay of AMPA-mediated current as well as the amplitude of the synaptic potential. Thus, the coupling between K_Na channels and AMPA receptors by synaptically induced Na⁺ transients represents an inherent negative feedback mechanism that scales down the magnitude of excitatory synaptic responses.     

Neuregulin-1 regulates LTP at CA1 hippocampal synapses through activation of dopamine D4 receptors

Neuregulin-1 (NRG-1) is genetically linked with schizophrenia, a neurodevelopmental cognitive disorder characterized by imbalances in glutamatergic and dopaminergic function. NRG-1 regulates numerous neurodevelopmental processes and, in the adult, suppresses or reverses long-term potentiation (LTP) at hippocampal glutamatergic synapses. Here we show that NRG-1 stimulates dopamine release in the hippocampus and reverses early-phase LTP via activation of D4 dopamine receptors (D4R). NRG-1 fails to depotentiate LTP in hippocampal slices treated with the antipsychotic clozapine and other more selective D4R antagonists. Moreover, LTP is not depotentiated in D4R null mice by either NRG-1 or theta-pulse stimuli. Conversely, direct D4R activation mimics NRG-1 and reduces AMPA receptor currents and surface expression. These findings demonstrate that NRG-1 mediates its unique role in counteracting LTP via dopamine signaling and opens future directions to study new aspects of NRG function. The novel functional link between NRG-1, dopamine, and glutamate has important implications for understanding how imbalances in Neuregulin-ErbB signaling can impinge on dopaminergic and glutamatergic function, neurotransmitter pathways associated with schizophrenia.     

Deleterious Effects of a Low Amount of Ethanol on LTP-Like Plasticity in Human Cortex

Ingesting ethanol (EtOH) at low doses during social drinking is a common human behavior for its facilitating effects on social interactions. However, low-dose EtOH may have also detrimental effects that so far are underexplored. Here we sought to test the effects of low-dose EtOH on long-term potentiation (LTP)-like plasticity in human motor cortex. Previous cellular experiments showed that low-dose EtOH potentiates extrasynaptic GABAAR and reduces NMDAR-mediated currents, processes that would limit the expression of LTP. Paired associative transcranial magnetic stimulation (PAS_LTP) was employed in nine healthy subjects for induction of LTP-like plasticity, indexed by a long-term increase in motor-evoked potential input–output curves. Synaptic α1-GABAAR function was measured by saccadic peak velocity (SPV). Very low doses of EtOH (resulting in blood concentrations of <5 mM) suppressed LTP-like plasticity but did not affect SPV when compared with a placebo condition. In contrast, 1 mg of alprazolam, a classical benzodiazepine, or 10 mg of zolpidem, a non-benzodiazepine hypnotic, decreased SPV but did not significantly affect LTP-like plasticity when compared with placebo. This double dissociation of low-dose EtOH vs alprazolam/zolpidem effects is best explained by the putatively high affinity of EtOH but not alprazolam/zolpidem to extrasynaptic GABAARs and to NMDARs. Findings suggest that enhancement of extrasynaptic GABAAR-mediated tonic inhibition and/or reduction of NMDAR-mediated neurotransmission by EtOH blocks LTP-like plasticity in human cortex at very low doses that are easily reached during social drinking. Therefore, low-dose EtOH may jeopardize LTP-dependent processes, such as learning and memory formation.