Calcium modulation in epilepsy

The ideal antiepileptic drug (AED) should correct the aberrant pathophysiology of epileptogenesis without interfering with normal neurotransmission A new group of drugs with antiepileptic efficacy, without sedative properties, would be an exciting prospect. Theoretical considerations and results from experimental animal models of epilepsy have put forward the possibility that calcium (Ca2+) antagonists may form such a group. The initiation of epileptogenic activity in the neuron is thought to be connected with the phenomenon known as "intrinsic burst firing", which is activated by an inward Ca2+ current. Ca2+ is described as the primary mediator of "excitotoxic" neuronal damage. Both necrotic and apoptotic cell death is associated with Ca2+ entry into the cells during status epilepticus. The Ca2+ channel blockers depressed epileptic depolarizations of neurons. In this review, we present anticonvulsant effects of cinnarizine, flunarizine, nifedipine, nimodipine, nicardipine, amlodipine, isradipine, niguldipine, diltiazem, verapamil and dantrolene in animal models of seizures. Also, a detailed analysis of interactions between Ca2+ blockers and AEDs was performed. Clinical trials in intractable epilepsy support to a certain degree antiepileptic properties of Ca2+ antagonists.     

Aristolactam BII of Saururus chinensis attenuates glutamate-induced neurotoxicity in rat cortical cultures probably by inhibiting nitric oxide production

Saurolactam and aristolactam BII, aristolactam-type alkaloids isolated from the aerial part of Saururus chinensis (Lour.) Ball (Saururaceae), showed significant neuroprotective activity against glutamate-induced toxicity in primary cultured rat cortical cells. The action mechanism of aristolactam BII, the more potent neuroprotective compound, was investigated using primary cultures of rat cortical cells as an in vitro system. Aristolactam BII attenuated glutamate-induced neurotoxicity significantly when it was added immediately or up to 9 h after the excitotoxic glutamate challenge. The alkaloid could not protect cultured neuronal cells from neurotoxicity induced by kainic acid or N-methyl- D-aspartate in a pre-treatment paradigm. However, aristolactam BII successfully reduced the overproduction of nitric oxide and the level of cellular peroxide in cultured neurons when it was treated as a post-treatment paradigm. These results may suggest that aristolactam BII exerts its significant neuroprotective effects on glutamate-injured primary cultures of rat cortical cells by directly inhibiting the production of nitric oxide.     

Meso-dihydroguaiaretic acid and licarin A of Machilus thunbergii protect against glutamate-induced toxicity in primary cultures of a rat cortical cells

1 We previously reported that four lignans isolated from the bark of Machilus thunbergii Sieb. et Zucc. (Lauraceae) protected primary cultures of rat cortical neurons from neurotoxicity induced by glutamate. 2 Among the lignans, meso-dihydroguaiarectic acid (MDGA) and licarin A significantly attenuated glutamate-induced neurotoxicity when added prior to or right after the excitotoxic glutamate challenge. 3 The neuroprotective activities of two lignans appeared to be more effective in protecting neurons against neurotoxicity induced by NMDA than that induced by kainic acid. 4 MDGA and licarin A diminished the calcium influx that routinely accompanies with the glutamate-induced neurotoxicity, and inhibited the subsequent overproduction of cellular nitric oxide and peroxide to the level of control cells. They also preserved cellular activities of antioxidative enzymes such as superoxide dismutase, glutathione peroxidase and glutathione reductase reduced in the glutamate-injured neuronal cells. 5 Thus, our results suggest that MDGA and licarin A significantly protect primary cultured neuronal cells against glutamate-induced oxidative stress, via antioxidative activities.     

Neuroprotective effects of a standardized extract of Diospyros kaki leaves on MCAO transient focal cerebral ischemic rats and cultured neurons injured by glutamate or hypoxia

Naoxinqing (NXQ, a standardized extract of Diospyros kaki leaves) is a patented and approved drug of Traditional Chinese Medicine (TCM) used for the treatment of apoplexy syndrome for years in China, but its underlying mechanism remains to be further elucidated. The present study investigates the effects of NXQ against focal ischemia/reperfusion injury induced by middle cerebral artery occlusion (MCAO) in rats and against glutamate-induced cell injury of hippocampal neurons as well as against hypoxia injury of cortical neurons. Oral administrations of NXQ at 20, 40, 80 mg/kg/day for 7 days (3 days before MCAO and 4 days after MCAO) significantly reduced the lesion of the insulted brain hemisphere and improved the neurological behavior of the rats. In primary rat hippocampal neuron cultures, treatment with NXQ at 5 - 20 microg mL concentration protects the neurons against glutamate-induced excitotoxic death in a dose-dependent manner. In primary rat cerebral cortical neuron cultures, pretreatment with 5 - 100 microg/mL NXQ also attenuates hypoxia-reoxygen induced neuron death and apoptosis in a dose-dependent manner. These results suggest that NXQ significantly protects the rats from MCAO ischemic injury in vivo and the hippocampal neurons from glutamate-induced excitotoxic injury as well as cortical neurons from hypoxia injury in vitro by synergistic mechanisms involving its antioxidative effects. NXQ:Naoxinqing CNS:central nervous system MCAO:middle cerebral artery occlusion I/R:ischemia and reperfusion.     

Inhibition of serum deprivation- and staurosporine-induced neuronal apoptosis by Ginkgo biloba extract and some of its constituents

Previous studies have already demonstrated that some constituents of an extract of Ginkgo biloba (EGb), such as ginkgolide B and bilobalide, protect cultured neurons from hypoxia- and glutamate-induced damage. This prompted us to investigate whether they were also able to inhibit neuronal apoptosis. We induced apoptosis in cultured chick embryonic neurons as well as in mixed cultures of neurons and astrocytes from neonatal rat hippocampus by serum deprivation and staurosporine. The increase in the percentage of apoptotic chick neurons from 12% in controls to 30% after 24 h of serum deprivation was reduced to control level by EGb (10 mg/l), ginkgolide B (10 microM), ginkgolide J (100 microM) and bilobalide (1 microM). After treatment with staurosporine (200 nM) for 24 h we observed 74% apoptotic chick neurons. This percentage of apoptotic neurons was reduced to 24%, 62% and 31% in the presence of EGb (100 mg/l), ginkgolide J (100 microM) and ginkgolide B (10 microM), respectively. Bilobalide (10 microM) decreased apoptotic damage induced by staurosporine treatment for 12 h nearly to the control level. In mixed neuronal/glial cultures, the extract of EGb (100 mg/l) and bilobalide (100 microM) rescued rat neurons from apoptosis caused by serum deprivation, whereas, bilobalide (100 microM) and ginkgolide B (100 microM) reduced staurosporine-induced apoptotic damage. Ginkgolide A revealed no anti-apoptotic effect in either serum-deprived or staurosporine-treated neurons. Our results suggest that EGb and some of its constituents possess anti-apoptotic capacity and that bilobalide is the most potent constituent.     

Neuroprotective effects of curculigoside against NMDA-induced neuronal excitoxicity in vitro

Glutamate is an important excitatory neurotransmitter in the central nervous system. Excessive accumulation of glutamate can cause excitotoxicity, which plays a key role in spinal cord injury, traumatic brain injury, stroke, and neurodegenerative diseases. Curculigoside (CCGS) is a major bioactive compound isolated from the rhizome of Curculigo orchioides Gaertn. CCGS has an extensive biological effect and has been used in Traditional Chinese Medicine. However, little is known about the neuroprotective effects of CCGS on glutamate-induced excitotoxicity. This study aims to evaluate the neuroprotective effects of CCGS in cultured cortical neurons. The results indicated that treatment with 1 and 10 μM CCGS evidently prevented N-methyl-d-aspartate (NMDA)-induced neuronal cell loss and reduced the number of apoptotic and necrotic cells in a time- and concentration-dependent manner. The neuroprotective effects of CCGS are related to down regulating the apoptotic protein levels and reducing the production of intracellular reactive oxygen species in cultured cortical neurons. These findings give a new insight into the development of natural anti-excitotoxicity agents.     

Decursinol and decursin protect primary cultured rat cortical cells from glutamate-induced neurotoxicity

We previously reported six neuroprotective decursinol derivatives, coumarins from Angelica gigas (Umbelliferae) roots. To elucidate the action patterns of decursinol derivatives, we investigated the neuroprotective effects of decursinol and decursin, which showed highly significant activity and were major constituents of A. gigas, using primary cultures of rat cortical cells in-vitro. At concentrations of 0.1-10.0 microM, both decursinol and decursin exerted a significant neuroprotective activity pretreatment and throughout treatment. In addition, decursin had a neuroprotective impact in the post-treatment paradigm implying that decursin might possess different action mechanisms from that of decursinol in the protection of neurons against glutamate injury. Both decursinol and decursin effectively reduced the glutamate-induced increased intracellular calcium ([Ca(2+)](i)) in cortical cells, suggesting that these two coumarins may exert neuroprotection by reducing calcium influx by overactivation of glutamate receptors. This suggestion was supported by the result that decursinol and decursin protected neurons against kainic acid (KA)-induced neurotoxicity better than against that induced by N-methyl-D-aspartate (NMDA). Moreover, both decursinol and decursin significantly prevented glutamate-induced decreases in glutathione, a cellular antioxidant, and glutathione peroxidase activity. In addition, both compounds efficiently reduced the overproduction of cellular peroxide in glutamate-injured cortical cells. These results suggested that both decursinol and decursin protected primary cultured rat cortical cells against glutamate-induced oxidative stress by both reducing calcium influx and acting on the cellular antioxidative defence system. Moreover, decursin is considered to probably have a different action mechanism from that of decursinol in protecting cortical cells against glutamate injury.     

知母皂苷元对谷氨酸引起的皮层神经元损伤的保护作用研究

目的观察知母皂苷元(Sarsasapogenin,SAR)对谷氨酸引起的皮层神经元损伤的保护作用。方法大鼠乳鼠大脑皮层神经元,培养7 d后用于实验。倒置相差显微镜观察神经元树突生长发育情况;用MTT法测定细胞活力;Ho-echst33258核染色观察细胞凋亡的形态学改变;Western印迹法检测神经元SYP、caspase-3、钙蛋白酶Ⅰ蛋白表达水平。结果形态学观察结果显示谷氨酸可明显抑制神经元树突的生长发育,表现为神经元树突总长度明显降低、一级树突数目明显减少、最大分支级数明显减少及胞体面积缩小。SAR(10、30、100μmol.L-1)可明显抑制谷氨酸对神经元树突生长发育的抑制作用,并呈明显浓度依赖。MTT和Ho-echst33258核染色结果显示谷氨酸可降低神经元细胞活力及增加神经元细胞凋亡百分比。SAR(10、30、100μmol.L-1)能明显对抗谷氨酸引起的神经元细胞活力降低及细胞凋亡百分比增加。Western印迹结果显示谷氨酸可明显降低SYP蛋白表达水平及增加活性caspase-3、钙蛋白酶Ⅰ蛋白表达水平。SAR(10、30、100μmol.L-1)可明显对抗谷氨酸引起SYP蛋白表达降低及活性caspase-3、钙蛋白酶Ⅰ蛋白表达增加。结论知母皂苷元能够明显对抗谷氨酸引起的皮层神经元损伤作用。     

E-p-methoxycinnamic acid protects cultured neuronal cells against neurotoxicity induced by glutamate

1. We previously reported that four new phenylpropanoid glycosides and six known cinnamate derivatives isolated from roots of Scrophularia buergeriana Miquel (Scrophulariaceae) protected cultured cortical neurons from neurotoxicity induced by glutamate. Here, we have investigated the structure-activity relationships in the phenylpropanoids using our primary culture system. 2. The alpha,beta-unsaturated ester moiety and the para-methoxy group in the phenylpropanoids appeared to play a vital role in neuroprotective activity. This suggested that E-p-methoxycinnamic acid (E-p-MCA) might be a crucial component for their neuroprotective activity within the phenylpropanoid compounds. E-p-MCA significantly attenuated glutamate-induced neurotoxicity when added prior to an excitotoxic glutamate challenge. 3. The neuroprotective activity of E-p-MCA appeared to be more effective in protecting neurons against neurotoxicity induced by NMDA than from that induced by kainic acid. E-p-MCA inhibited the binding of [propyl-2,3-(3)H]-CGP39653 and [2-(3)H]-glycine to their respective binding sites on rat cortical membranes. However, even high concentrations of E-p-MCA failed to inhibit completely [propyl-2,3-(3)H]-CGP39653 and [2-(3)H]-glycine binding. 4. Indeed, E-p-MCA diminished the calcium influx that routinely accompanies glutamate-induced neurotoxicity, and inhibited the subsequent overproduction of nitric oxide and cellular peroxide in glutamate-injured neurons. 5. Thus, our results suggest that E-p-MCA exerts significant protective effects against neurodegeneration induced by glutamate in primary cultures of cortical neurons by an action suggestive of partial glutamatergic antagonism.     

Protective Effect of Gabapentin on N-methyl-D-aspartate–Induced Excitotoxicity in Rat Hippocampal CA1 Neurons

Gabapentin was developed as an anticonvulsant, but has also been used to alleviate hyperalgesia in neuropathic pain. In this study, the protective effect of gabapentin against N-methyl-D-aspartate (NMDA)-induced excitotoxicity in rat hippocampal CA1 neurons was investigated. Pre-treatment with gabapentin reduced the degree of neuronal damage induced by NMDA exposure in cultured hippocampal slices. Patch-clamp studies revealed that gabapentin significantly inhibited the NMDA receptor–activated ion current in dissociated hippocampal CA1 neurons, resulting in suppression of glutamate-induced neuronal injury. These results show that gabapentin may exert protective effects against glutamate-induced neuronal injury at least in part by inhibiting the NMDA receptor–activated ion current.     

Apparent Independent Action of Nimodipine and Glutamate Antagonists to Protect Cultured Neurons Against Glutamate-induced Damage

A disturbed cellular calcium homeostasis is suggested to play a pivotal role in neuronal damage. Energy deficiency causes depolarization of the neuronal membrane and Ca²⁺ enters the cells through different ion channels, the voltage-sensitive L-type Ca²⁺ channels and the NMDA-operated channels being the main gates. In the present study we used primary cultures of rat hippocampal neurons to demonstrate that the dihydropyridine calcium antagonist nimodipine, the non-competitive NMDA antagonists dizocilpine and memantine, as well as the AMPA antagonist NBQX (2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo(F)quinoxaline), attenuate the glutamate-induced neuronal damage dose-dependently. Nimodipine applied simultaneously with NMDA-antagonists and NBQX, respectively, resulted in somewhat greater neuroprotection of glutamate-treated neurons compared with the effects of these agents applied singly. The type of interaction is best described by an independent action in combination, which means that the relative effects of nimodipine were not enhanced. Therefore, it can be considered as a lack of potentiation. © 1997 Elsevier Science Ltd. All rights reserved.     

Comparison of the calcium entry blockers nimodipine and flunarizine on human cerebral and temporal arteries: role in cerebrovascular disorders

Summary The effect of the calcium entry blockers flunarizine and nimodipine on isolated human cerebral and temporal arteries has been studied.Flunarizine induced only weak relaxation of precontracted temporal arteries in contrast to the response seen in cerebral arteries. Nimodipine invariably induced strong relaxation of both types of vessel. The effect of the calcium entry blockers on potassium (K⁺)-, noradrenaline (NA)- and 5-hydroxytryptamine (5-HT)-induced contraction was also examined. In general, the K^–-induced contraction was inhibited by both calcium entry blockers, nimodipine being more potent than flunarizine, the cerebral artery being more sensitive. The response to K⁺ consisted of two phases; the second, slowly developing phase of contraction was more sensitive to either blocker than the initial, fast phase of contraction.Flunarizine was significantly more potent in inhibiting NA-induced contraction of the human cerebral than of the temporal artery, and there was no difference in its action on 5-HT-induced contraction of either artery. The same pattern was found for nimodipine, which was more potent in every aspect. Both calcium entry blockers induced a parallel shift in calcium-induced contraction studied by application of calcium to vessels preincubated in calcium free medium. Flunarizine was more potent on cerebral than on temporal arteries and there was no difference between the two vessels in this action of nimodipine. However, the latter was more potent than flunarizine in preventing calcium-induced contraction.The clinical implications of the two agents are discussed in relation to cerebrovascular disorders.     

氯通道阻断剂对NO诱导离体大鼠海马神经元凋亡的保护作用

目的观察氯通道阻断剂SITS和DIDS对NO诱导的大鼠离体海马神经元凋亡的保护作用。方法离体培养12d的SD大鼠海马神经元,随机分为正常对照组、NO处理组、NO处理后使用氯通道阻断剂组,对各组神经元分别在相应的时间点进行Hoechst荧光染色观察凋亡细胞数和MTT实验定量检测神经元的存活率,Western blot分析凋亡信号分子Caspase-3的变化。结果SITS和DIDS呈剂量依赖性地抑制NO诱导的神经元损伤,并能抑制损伤所引起的Caspase-3的激活,提高神经元的存活率。结论氯通道阻断剂对NO诱导的大鼠海马神经元凋亡有一定的保护作用。     

Propentofylline protects beta-amyloid protein-induced apoptosis in cultured rat hippocampal neurons

beta-Amyloid protein 1-42 (beta42) can induce apoptosis in the cultured hippocampal neurons, suggesting that it plays an important role in causing neurodegeneration in Alzheimer's disease. Recently, propentofylline, a synthetic xanthine derivative, has been reported to depress ischemic degeneration of hippocampal neurons in gerbils. The present study investigated whether or not propentofylline affected the beta42-induced apoptosis of hippocampal neurons, and if so, which type of signaling machinery works in the neuroprotective action of propentofylline. Addition of propentofylline markedly attenuated the beta42-induced cell death of rat hippocampal neurons. The amyloid protein certainly induced apoptosis in the cultured hippocampal cells revealed by nuclear condensation, caspase-3 activation and an increase of Bax. Intriguingly, propentofylline blocked both the apoptotic features induced by beta42 and further induced an anti-apoptotic protein, Bcl-2, during a short time of incubation. The neuroprotective action of propentofylline was comparably replaced with dibutyryl cAMP (dbcAMP) and was completely suppressed by a low concentration of specific protein kinase A (PKA) inhibitor. Taken altogether, the data strongly suggest that the protection of propentofylline on the beta42-induced neurotoxicity is caused by enhancing anti-apoptotic action through cAMP-PKA system. Propentofylline as a therapeutic agent to Alzheimer's disease is discussed.     

Dammarane derivatives protect cultured rat cortical cells from glutamate-induced neurotoxicity

We previously reported that ginsenosides Rb1 and Rg3, dammarane glycosides, of Panax ginseng C. A. Meyer (Araliaceae), significantly attenuated glutamate-induced neurotoxicity in primary cultures of rat cortical cells. To seek more potent neuroprotective compounds, we attempted to modify the chemical structure of dammarane glycosides and obtained six derivatives, MA-11, PT-11, PT-111, POA-101, POA-111 and N-001. The neuroprotective activity of these dammarane derivatives were evaluated employing primary cultures of rat corticoid cells. The glutamate-induced neuronal cell damage was significantly reduced by a pre-treatment with protopanaxadiol, MA-11 or PT-11 at concentrations ranging from 100 nM to 10 microM. Both MA-11 and PT-11, preserved the levels of catalase and inhibited decreases in glutathione reductase in glutamate-injured cells. Furthermore, the dammarane derivatives reduced the content of intracellular peroxide in glutamate-intoxicated cells. Finally, they inhibited the formation of malondialdehyde, a compound produced during lipid peroxidation, in glutamate-insulted cells. These results show that the dammarane derivatives, MA-11 and PT-11, exert significant neuroprotective effects on cultured cortical cells by a mechanism seemingly distinct from that afforded by ginsenosides Rb1 and Rg3. As such, the dammarane derivatives may be efficacious in protecting neurons from oxidative damage caused by exposure to excess glutamate.     

阿托伐他汀对谷氨酸引起大鼠神经元损伤保护作用机制的研究

目的探讨阿托伐他汀对谷氨酸所致培养大鼠皮层神经元损伤保护作用的机制。方法 MTT法测定细胞存活率;Hoechst33258核染色观察细胞凋亡的形态学改变;Western blot检测活性的半胱氨酸天冬氨酸蛋白酶-3(caspase-3)和钙蛋白酶Ⅰ蛋白表达水平。结果谷氨酸(100μmol.L-1)可使神经元细胞存活率下降,细胞凋亡百分比明显增加,活性的caspase-3和钙蛋白酶Ⅰ蛋白表达增加。阿托伐他汀明显对抗谷氨酸诱导的神经元存活率下降及细胞凋亡百分比增加,同时明显抑制活性的caspase-3和钙蛋白酶Ⅰ蛋白表达增加。磷酯酰肌醇-3激酶(phos-phoinositide3-kinase,PI3K)/磷酸化蛋白激酶B(protein ki-nase B,Akt)通路特异性阻断剂LY294002(10μmol.L-1)能抑制阿托伐他汀对抗谷氨酸引起神经元细胞存活率下降,细胞凋亡百分比增加及活性caspase-3和钙蛋白酶Ⅰ蛋白表达增加的作用。结论阿托伐他汀能够明显对抗谷氨酸引起的皮层神经元损伤作用,这种作用可能与激活PI3K/Akt信号转导通路有关。     

知母皂苷元对高糖引起的体外培养大鼠海马神经元损伤的保护作用

目的探讨知母皂苷元(sarsasapogenin,Sar)对高糖引起的海马神经元损伤是否有保护作用。方法选用出生0～24 h Sprague-Dawley(SD)大鼠乳鼠,取海马,进行海马神经元体外培养,培养7 d用于实验。实验分为正常对照组、高糖组、高糖+Sar(10、30、100μmol.L-1)组;对照组:加入等量含0.1%DMSO培养基;高糖处理组:分别加入葡萄糖(30、50、100 mmol.L-1)作用48 h;高糖+Sar(10、30、100μmol.L-1)组:先加入不同浓度Sar(10、30、100μmol.L-1)作用1 h,然后加入葡萄糖(50 mmol.L-1)作用48 h;应用MTT方法观察细胞活力,免疫荧光和Western免疫印迹方法观察神经元突触素表达的改变。应用Hoechst 33258核染色检测神经元凋亡。应用Western免疫印迹方法观察caspase-3和多聚ADP核糖聚合酶(PARP)蛋白表达改变。结果加入葡萄糖(30、50、100 mmol.L-1)作用48 h可使培养神经元细胞活力明显降低,神经元突触素蛋白表达明显降低。另外高糖也可引起神经元凋亡细胞百分比和活性caspase-3、PARP蛋白表达水平也较对照组明显提高。在加入高糖前加入不同浓度Sar(10、30、100μmol.L-1)可明显对抗高糖引起的这些变化。培养海马神经元突触素蛋白表达较高糖组(50 mmol.L-1)明显增加,神经元凋亡细胞百分比和活性caspase-3、PARP蛋白表达水平也较高糖组明显降低。结论 Sar对高糖引起的海马神经元损伤具有明显的保护作用。     

In vitro neuroprotective activities of phenylethanoid glycosides from Callicarpa dichotoma

Ten phenylethanoid glycosides, forsythoside B, acteoside, 2'-acetylacteoside, poliumoside, brandioside, echinacoside, isoacteoside, cistanoside H and E-tubuloside E as well as a new compound, Z-tubuloside E, were isolated from the n-BuOH fraction of Callicarpa dichotoma Raeuschel (Verbenaceae) by bioactivity-guided fractionation using glutamate-injured primary cultures of rat cortical cells as a screening system. These phenylethanoid glycosides significantly attenuated glutamate-induced neurotoxicity at concentrations ranging from 0.1 to 10 microM.     

Cardiovascular and renal actions of calcium channel blocker chemical subgroups: a search for renal specificity

The diuretic and natriuretic responses to structurally distinct classes of Ca2+ channel blockers have been compared, to determine whether any agent provoked K+-sparing natriuresis, and to assess the relation of such responses with drug effects on blood pressure. Conscious normotensive Sprague-Dawley rats received vehicle or one of the following drugs in an oral saline load (40 mL kg-1) nifedipine, nimodipine, nitrendipine, prenylamine, cinnarizine, flunarizine, diltiazem, verapamil, hydrochlorothiazide, amiloride, or hydralazine, at doses from 0.316 to 100 mg kg-1. Urine was collected for 6h. Blood pressure was monitored directly in parallel studies. Diltiazem (31.6, 100 mg kg-1) and flunarizine (100 mg.kg-1) enhanced urine and electrolyte excretion in spite of marked hypotension; diltiazem was the only drug to produce dose-related renal responses. In contrast, equihypotensive doses of hydralazine and nifedipine produced overt urine and electrolyte retention. Nitrendipine and prenylamine (0.316 mg kg-1 each) produced slight diuresis or natriuresis without altering blood pressure; higher doses had no effect. The 31.6 mg kg-1 doses of verapamil, nitrendipine, and nimodipine markedly reduced blood pressure, but neither enhanced nor limited urine and electrolyte excretion. Cinnarizine failed to produce any cardiovascular or renal effects. Diuretic responses evoked by the Ca2+ channel blockers were not class-specific, showed no tendency towards sparing K+, were generally weaker than those produced by low doses of amiloride or hydrochlorothiazide, and were dissociable from drug-induced changes in blood pressure.     

The neuroprotective action of pyrroloquinoline quinone against glutamate-induced apoptosis in hippocampal neurons is mediated through the activation of PI3K/Akt pathway

Pyrroloquinoline quinone (PQQ), a cofactor in several enzyme-catalyzed redox reactions, possesses a potential capability of scavenging reactive oxygen species (ROS) and inhibiting cell apoptosis. In this study, we investigated the effects of PQQ on glutamate-induced cell death in primary cultured hippocampal neurons and the possible underlying mechanisms. We found that glutamate-induced apoptosis in cultured hippocampal neurons was significantly attenuated by the ensuing PQQ treatment, which also inhibited the glutamate-induced increase in Ca2+ influx, caspase-3 activity, and ROS production, and reversed the glutamate-induced decrease in Bcl-2/Bax ratio. The examination of signaling pathways revealed that PQQ treatment activated the phosphorylation of Akt and suppressed the glutamate-induced phosphorylation of c-Jun N-terminal protein kinase (JNK). And inhibition of phosphatidylinositol-3-kinase (PI3K)/Akt cascade by LY294002 and wortmannin significantly blocked the protective effects of PQQ, and alleviated the increase in Bcl-2/Bax ratio. Taken together, our results indicated that PQQ could protect primary cultured hippocampal neurons against glutamate-induced cell damage by scavenging ROS, reducing Ca2+ influx, and caspase-3 activity, and suggested that PQQ-activated PI3K/Akt signaling might be responsible for its neuroprotective action through modulation of glutamate-induced imbalance between Bcl-2 and Bax.