钙离子对4-氨基吡啶诱发肥大细胞释放组胺作用的影响

4-Aminopyridine(4-AP) has been shown to induce histamine release fromisolated peritoneal mast cells(PMC)in mice and rats. In the presence of extracellular calcium atnormal level(0.9 mmol·L^-1)histamine release induced by 4-AP(13. 6 mmol·L^-1) from mice PMCwas 33.0%±4.6%,while at low calcium concentration (0.5 mmol·L^-1) and in calcium-freemedium this parameter decreased to 25.5%±4.2%and 16.3%±3.7%respectively.Histaminerelease in response to 4-AP(10 mmol·L^-1)from rat PMC was 39.1%±6.7%(0.9 mmol·L^-1calcium),while at low calcium concentration(0. 5 mmol·L^-1) and in calcium-free medium thisparameter decreased to 29.3%±4.7%and 20.2%±2.9% respectively. Results of statisticalanalysis indicate that 4-AP induced histamine release is related to Ca²⁺ concentration. When rat PMCwere preincubated in calcium-free medium with EDTA 0.1 mmol·L^-1 for 180 min　4-AP inducedhistamine release was 13.8%±1.6%.This shows that 4-AP also elicited mobilization of endogenous calcium stores in mast cells.The mechanism of 4-AP　induced histamine release was discussed.     

In vivo effects of the NMDA receptor agonist tetrazolyl-glycine related to the function of small-diameter primary afferents

The NMDA receptor agonist tetrazolyl-glycine (TG; 100 μg kg^–1, i.v.) caused a depressor reflex in anaesthetized rats. The NMDA receptor antagonist MK-801 (300 μg kg^–1, i.v.) inhibited this depressor reflex, but not that induced by pentylenetetrazol (PTZ; 100 mg kg^–1, i.v.), indicating a selective effect of TG on NMDA receptors in vivo. Capsaicin pretreatment, which excludes the function of small-diameter primary afferent fibres, caused only a reduction of the TG-induced depressor reflex, suggesting a reduction of NMDA receptors. The absence of effects of TG and PTZ on the blood pressure in pithed rats excluded any peripheral vascular actions of TG and PTZ. The depressor reflex evoked by afferent nerve stimulation was also inhibited by MK-801 (300 μg kg^–1, i.v.), but not by the tachykinin antagonist L-742694 (10 mg kg^–1, i.v.), confirming the essential role of glutamate in the neurotransmission of signals at central terminals of small-diameter afferent neurons. Plasma protein extravasation in the rat hind paw, induced by neurotransmitters released at peripheral terminals of small diameter afferent neurons by antidromic nerve stimulation, was not influenced by MK-801, indicating that glutamate is either not released or has no effect there. It is concluded that the NMDA agonist TG is a valuable tool to study the functions of primary afferents in vivo. Received: 8 February 1999 / Accepted: 12 April 1999 / Published online: 21 June 1999     

Differential desensitization of ionotropic non-NMDA receptors having distinct neuronal location and function

The release of tritium from rat hippocampal synaptosomes prelabeled with [³H]noradrenaline ([³H]NA) or [³H]5-hydroxytryptamine ([³H]5-HT) and from rat neocortex synaptosomes prelabeled with [³H]choline and the release of endogenous GABA and glutamate from rat neocortex synaptosomes were monitored during superfusion with media containing varying concentrations of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) or kainic acid. Concentration-dependent release potentiations were elicited by both excitatory amino acids (EAAs) in all the transmitter systems investigated. The releases evoked by 100 μM AMPA were, in all cases, almost totally dependent on external Ca²⁺ and sensitive to 6,7-dinitroquinoxaline-2,3-dione (DNQX), indicating involvement of non-NMDA receptors. When cyclothiazide, a drug able to prevent desensitization of AMPA-preferring receptors, was added to the superfusion medium (at 1 or 10 μM) concomitantly with 100 μM AMPA or kainate, the EAA-evoked release of [³H]NA was significantly enhanced. Concanavalin A, a lectin thought to prevent desensitization of kainate-preferring receptors, had no effect (up to 10 μM) on the release of [³H]NA evoked by AMPA or kainate. The effect of cyclothiazide was lost if, after an 8-min pretreatment, the drug was removed just before the AMPA stimulus. When added concomitantly with the EAAs, cyclothiazide potentiated the release of [³H]5-HT elicited by AMPA and, less so, that evoked by kainate. Concanavalin A was ineffective. Neither cyclothiazide (1 or 10 μM) nor concanavalin A (3 or 10 μM) could affect the release of [³H]ACh or endogenous GABA provoked by 100 μM AMPA or kainate, suggesting that the receptors involved do not desensitize. Exposure of neocortex synaptosomes to AMPA or kainate concomitantly with cyclothiazide caused endogenous glutamate release that did not differ from that evoked by the EAAs alone. In contrast, the effects of AMPA and kainate were potentiated by concanavalin A. The activity of the lectin (3 μM) persisted when it was applied for 8 min and then removed before the AMPA or kainate (100 μM) pulse. When hippocampal synaptosomes prelabeled with [³H]NA were subjected to three subsequent AMPA (100 μM) stimuli (S₁, S₂ and S₃), the release of [³H]NA decreased dramatically from S₁ to S₃ (S₃/S₁ = 0.14 ± 0.04); a significant ‘protection’ of the AMPA effect was offered by 1 μM cyclothiazide (S₃/S₁ = 0.36 ± 0.06). This value did not differ from the S₃/S₁ ratio (0.38 ± 0.04) obtained in parallel experiments with 12 mM K⁺. The release evoked by high-K⁺ was insensitive to cyclothiazide. Finally, the effect of AMPA on the release of [³H]ACh did not respond to cyclothiazide also during three subsequent stimuli with 100 μM AMPA. To conclude: a) ionotropic non-NMDA receptors mediating enhancement of NA, 5-HT, ACh, GABA and glutamate release exist on the corresponding nerve terminals; b) the receptors present on noradrenergic and serotonergic neurons are AMPA-preferring receptors, whereas the glutamate autoreceptors resemble most the kainate-preferring subtype; the receptors mediating ACh and GABA release can not be subclassified at present; c) desensitization may not be a property of all non-NMDA ionotropic receptors. The receptors here characterized represent five models of native non-NMDA receptors suitable for pharmacological and molecular studies. Received: 28 January 1997 / Accepted: 14 April 1997     

4-氨基吡啶对牛磺酸调节突触体氨基酸释放的影响

AIM　To elucidate the mechanism of taurine-regulated amino acid release from synaptosomes. METHODS　Endogenous aspartate, glutamate and GABA release from cortical synaptosomes were measured by high performance liquid chromatography using stepwise elution system, Glutamate release was monitored by continuous fluorometry. RESULTS　4-Aminopyridine (3.0×10^-2 mol*L^-1) counteracted the taurine-induced inhibition of glutamate overflow (P<0.05), while aspartate and GABA release was not affected. Nimodipine (10^-5 mol*L^-1) combined with 4-aminopyridine was shown to decrease glutamate release (P<0.05). CONCLUSION　Taurine may regulate glutamate release through presynaptic L-type calcium channel and aslo act on Asp-and GABA-nereve terminal to regulate Asp and GABA release in rat cortex.     

Hyperlocomotion and increased dopamine efflux in the rat nucleus accumbens evoked by electrical stimulation of the ventral subiculum: role of ionotropic glutamate and dopamine D1 receptors

Rationale and objectives: The role of glutamatergic afferents from the hippocampus in the modulation of dopamine (DA) efflux in the nucleus accumbens (NAcc) and concomitant increases in locomotor activity was examined following brief high-frequency electrical stimulation of the ventral subiculum (vSub). Reverse dialysis of ionotropic glutamate receptor (iGluR) antagonists into the NAcc identified the relative contributions of N-methyl-d-aspartate (NMDA) and non-NMDA glutamate receptors in the modulation of DA efflux, whereas microinjection of these compounds or selective DA D₁ or D₂ receptor antagonists were used to analyze the roles of glutamatergic and DA receptors in the stimulation-induced hyperlocomotion. Methods and results: Electrical stimulation of the vSub at 20 Hz (10 s, 300 μA) induced a significant increase in (1) DA levels in the NAcc (≈30% from pre-stimulation DA levels) and (2) locomotor activity (≈400%). The evoked DA release was completely blocked by reverse dialysis of a selective non-NMDA antagonist DNQX (10 μM and 100 μM), whereas only a high dose of the NMDA antagonist AP-V (100 μM) was effective. The increased motor activity, however, was only slightly attenuated by reverse dialysis of these drugs. Bilateral intra-NAcc injection of DNQX (1 μg/0.5 μl) blocked the increased motor activity induced by vSub stimulation relative to saline treatment. In contrast, bilateral intra-NAcc injection of AP-V (1 μg/ 0.5 μl) alone caused a significant increase in locomotor activity. The increased motor activity induced by vSub stimulation appears to be mediated through the DA D₁ receptor, as systemic administration of the D₁ antagonist SCH 23390 (0.25 mg/kg and 1 mg/kg), but not the D₂ antagonist sulpiride (2 mg/kg and 10 mg/kg) blocked these effects. Conclusions: These data indicate an important role for hippocampal glutamatergic afferents in modulating the release of DA through iGluR on DA-receptive neurons in the NAcc and possibly on output neurons to the ventral tegmental area, which subsequently elicits a prolonged increase in locomotor behavior. The role of this circuit in mediating context-dependent behavioral sensitization to repeated administration of psychostimulants is discussed. Received: 13 October 1999 / Accepted: 21 December 1999     

阿克他利对佐剂性关节炎大鼠腹腔巨噬细胞分泌IL-1和T淋巴细胞亚群的影响

Effects of actarit on production of interleukin-1（IL-1）by peritoneal macrophages from adjuvant arthritis(AA) rats ex vivo and the ratio of subpopulation of T lymphocytes in AA rats ex vivo and the production of hydrogen peroxide （H₂O₂）by peritoneal macrophages of mice in vitro were studied. The results showed that IL-1 synthesis from the adherent peritoneal macrophages induced with lipopolysaccharide (8 mg·L^-1) in AA rats in vivo were inhibited by actarit; the ratio of L₃T₄⁺/Lyt-2⁺ was lowered after administrating actarit; and H₂O₂ release of the peritoneal macrophages of mice was reduced in dose-dependent manner. The data suggest that the therapeutic effects of actarit on AA rats be related to inhibition of production of IL-1 and reduction of H₂O₂ release and lowered rat io of L₃T₄⁺/Lyt-2⁺ T-lymophocyte.     

Environmental enrichment decreases intravenous amphetamine self-administration in rats: dose-response functions for fixed- and progressive-ratio schedules

Rationale: Recent case series suggest that chromium picolinate in doses of 400 μg daily may have antidepressant properties, perhaps through increasing the peripheral availability of tryptophan for brain serotonin (5-HT) synthesis. Objectives: To determine the effects of chromium treatment on plasma tryptophan availability and on brain 5-HT function in human and animal models. Methods: We studied the effects of short-term chromium supplementation on plasma concentrations of tryptophan and other large neutral amino acids. Brain 5-HT function was assessed by measuring the corticosterone/cortisol response to the 5-HT precursor, 5-hydroxytryptophan (5-HTP), a response believed to be mediated via indirect activation of 5-HT_2A receptors. Results: In rats, chromium increased peripheral and central tryptophan availability and elevated brain 5-HT content. Changes in peripheral tryptophan availability were not seen in humans but in both rats and humans, chromium lowered the cortisol response to challenge with 5-HTP. Conclusions: Chromium can modify brain 5-HT function in humans and animals, perhaps by altering the sensitivity of central 5-HT_2A receptors. Electronic Publication     

The role of NMDA and non-NMDA receptors in the NTS in mediating three distinct sympathoinhibitory reflexes

Cholecystokinin (CCK) elicits a sympathetic vasomotor reflex that is implicated in gastrointestinal circulatory control. We sought to determine (1) the site in the solitary tract nucleus (NTS) responsible for mediating this reflex and (2) the possible involvement of excitatory amino acid (EAA) receptors. In addition, we sought to determine whether the NTS site responsible for mediating the baroreflex (phenylephrine, PE, 10 μg/kg i.v.) and the von Bezold–Jarisch reflex (phenylbiguanide, PBG, 10 μg/kg i.v) overlap with that involved in the CCK-induced reflex (CCK, 4 μg/kg, i.v.), and to compare the relative importance of NMDA and non-NDMA receptors in these reflexes. In separate experiments, the effects of PE, PBG, and CCK on mean arterial blood pressure, heart rate, and splanchnic sympathetic nerve discharge were tested before and after bilateral microinjection into the NTS of the γ-aminobutyric acid_A (GABA_A) agonist muscimol, the EAA antagonist kynurenate, the NMDA receptor antagonist d(−)-2-amino-5-phosphopentanoic acid (AP-5), the non-NMDA receptor antagonist 1,2,3,4-tetrahydro-6-nitro-2,3-dioxo-benzo[f]quinoxaline-7-sulfonamide (NBQX), AP-5 + NBQX, or vehicle. While all treatments (except vehicle) significantly attenuated/abolished/reversed the splanchnic sympathoinhibitory responses to PE, PBG, and CCK, the extent of blockade varied between the different treatment groups. Both NMDA and non-NMDA receptors were essential to the baroreflex and the von Bezold–Jarisch reflex, whereas the CCK reflex was more dependent on non-NMDA receptors. Muscimol, kynurenate, and AP-5 + NBQX significantly attenuated the bradycardic responses to PE and PBG (P < 0.05), whereas AP-5, NBQX, or vehicle did not. The bradycardic responses to CCK remained intact after all treatments. These results suggest that while there is overlap in the area of the NTS responsible for eliciting all three reflexes, NMDA and non-NMDA receptors are recruited differentially for the full expression of these reflexes. The CCK-induced sympathoinhibitory reflex is unique in that it relies predominantly on non-NMDA receptors in the NTS and elicits bradycardic effects that are independent of the NTS.     

LC-MS/MS法测定人血浆中西酞普兰及其在制剂生物等效性中的应用

A sensitive and selective LC-MS/MS method for determination of citalopram in human plasma was established to study the bioequivalence of different formulations containing citalopram. The samples were simply pretreated by protein precipitation using acetonitrile, and then analyzed on a Zorbax Extend C₈column. The mobile phase consisted of acetonitrile-water-formic acid (60∶40∶0.2), at a flow-rate of 0.5 mL·min^-1. A Thermo Finnigan TSQ Quantum Ultra tandem mass spectrometer equipped with electrospray ionization source was used as detector and was operated in the positive ion mode. Selected reaction monitoring using the precursor to product ion combinations of m/z325 → m/z109 and m/z265 → m/z167 was performed to quantify citalopram and the internal standard, respectively. The pharmacokinetic parameters of citalopram in different formulations were calculated by non-compartment model. The linear calibration curves were obtained in the concentration range of 0.10-100 μg·L^-1. The lower limit of quantification was 0.10 μg·L^-1. The intra- and inter-day relative standard deviation (RSD) over the entire concentration range was less than 5.2%. Accuracy determined at three concentrations (0.25, 8.00 and 90.0 μg·L^-1 for citalopram) ranged from -4.7% to 1.3%. Each plasma sample was chromatographed within 3.0 min. The method was successfully used in bioequivalence study of citalopram in human plasma after oral administration of 20 mg citalopram. Calculated with AUC_{1-120 h}, the bioavailability of two formulations was (102.1±10.9)%. The method is rapid, selective, robust and is proved to be suitable for bioequivalence evaluation of different formulations containing citalopram.     

Neural circuits and nicotinic acetylcholine receptors mediate the cholinergic regulation of midbrain dopaminergic neurons and nicotine dependence

Midbrain dopaminergic(DA)neurons are governed by an endogenous cholinergic system,originated in the mesopontine nuclei.Nicotine hijacks nicotinic acetylcholine receptors(nAChRs)and interferes with physiological function of the cholinergic system.In this review,we describe the anatomical organization of the cholinergic system and the key nAChR subtypes mediating cholinergic regulation of DA transmission and nicotine reward and dependence,in an effort to identify potential targets for smoking intervention.Cholinergic modulation of midbrain DA systems relies on topographic organization of mesopontine cholinergic projections,and activation of nAChRs in midbrain DA neurons.Previous studies have revealed thatα4,α6,andβ2 subunit-containing nAChRs expressed in midbrain DA neurons and their terminals in the striatum regulatefirings of midbrain DA neurons and activity-dependent dopamine release in the striatum.These nAChRs undergo modification upon chronic nicotine exposure.Clinical investigation has demonstrated that partial agonists of these receptors elevate the success rate of smoking cessation relative to placebo.However,further investigations are required to refine the drug targets to mitigate unpleasant side-effects.     

胞内钙离子浓度与咖啡因保护小脑颗粒神经元作用的关系

用凝胶电泳和fura-2荧光技术测定［Ca²⁺］_i方法研究咖啡因对低钾诱导的大鼠小脑颗粒神经元凋亡的保护作用与［Ca²⁺］_i升高之间的关系. 将体外培养的小脑颗粒神经元从高钾（25 mmol·L^-1 KCl）培养基中转移到低钾（5 mmol·L^-1 KCl）培养基中,神经元发生凋亡. 但低钾引起的神经元死亡可被咖啡因（5-20 mmol·L^-1）浓度依赖性地保护,且咖啡因的这种作用不受蓝尼定(ryanodine) 敏感钙释放阻断剂蓝尼定和丹曲林(dantrolene)的影响;也不被Ｌ-型钙通道阻断剂硝苯地平, 尼莫地平, 维拉帕米和NMDA受体阻断剂地佐环平抑制. 结果说明［Ca²⁺］_i的升高并不是咖啡因对小脑颗粒神经元的保护作用所必需的.     

吗啡增强谷氨酸单钠神经毒性及其作用机制

用皮层神经细胞体外培养、形态学观察、单个神经细胞内游离钙检测及乳酸脱氢酶(LDH)测定等方法,观察了吗啡对谷氨酸单钠(MSG)神经毒性增强作用以及纳洛酮对吗啡作用的逆转,分析了其可能的作用机制。结果表明:吗啡能显著增强的MSG的细胞毒作用.纳络酮可逆转这种增强作用,细胞内Ca²⁺超载可能是兴奋性神经毒素引起神经元死亡的共同病理学机制。     

胞内钙离子浓度与咖啡因保护小脑颗粒神经元作用的关系(英文)

用凝胶电泳和 fura- 2荧光技术测定 [Ca2 + ]i方法研究咖啡因对低钾诱导的大鼠小脑颗粒神经元凋亡的保护作用与 [Ca2 + ]i 升高之间的关系 .将体外培养的小脑颗粒神经元从高钾 ( 2 5mmol· L-1KCl)培养基中转移到低钾 ( 5mmol· L-1KCl)培养基中 ,神经元发生凋亡 .但低钾引起的神经元死亡可被咖啡因 ( 5- 2 0 mmol· L-1)浓度依赖性地保护 ,且咖啡因的这种作用不受蓝尼定 ( ryanodine) -敏感钙释放阻断剂蓝尼定和丹曲林 ( dantrolene)的影响 ;也不被 L-型钙通道阻断剂硝苯地平 ,尼莫地平 ,维拉帕米和 NMDA受体阻断剂地佐环平抑制 .结果说明 [Ca2 + ]i 的升高并不是咖啡因对小脑颗粒神经元的保护作用所必需的 .     

Excitotoxic potential of the cyanotoxin β-methyl-amino-l-alanine (BMAA) in primary human neurons

The toxicity of the cyanobacterial modified amino acid, BMAA, has been described in rat, mouse and leech neurons. Particular emphasis has been placed on the potential ability of BMAA to induce neuronal damage via excitotoxic mechanisms. Here we present data indicating that the effects observed on lower organisms are also evident in a human model. Our data indicates that BMAA induces increased intracellular Ca²⁺ influx, DNA damage, mitochondrial activity, lactate dehydrogenase (LDH) release and generation of reactive oxygen species (ROS). The amelioration of LDH release in the presence of the N-methyl-d-aspartate (NMDA) receptor antagonist MK801 indicates that the neurotoxic effects of BMAA are mediated via NMDA receptor activation. Additionally, we have shown that BMAA induces the expression of neuronal nitric oxide synthase (nNOS) and caspase-3 indicating that it can stimulate apoptosis in human neurons, presumably via activation of NMDA receptors.     

Alcohol withdrawal reaction as a result of adaptive changes of excitatory amino acid receptors

Summary Recent electrophysiological and biochemical studies suggest that ethanol interferes with excitatory amino acid (EAA) neurotransmission. Here, we present electrophysiological evidence that, following cessation of a chronic ethanol treatment, noradrenergic locus coeruleus (LC) neurons display hyperactivity at the same time as a specifically enhanced sensitivity to microiontophoretically applied NMDA or quisqualate. Furthermore, after chronic ethanol treatment, but not before, the NMDA receptor antagonist MK 801 (0.3–2.4 mg/kg, i.v.) dose-dependently inhibited the firing of the LC neurons. Our data indicate that an up-regulation of EAA receptors located on LC neurons accounts for the changes in LC firing in ethanol-treated rats. We propose that activation of the LC contributes to the clinical signs of the ethanol abstinence reaction and that EAA antagonists may be beneficial therapeutically for its treatment. Correspondence to G. Engberg at the above address     

Evidence for strychnine-sensitive glycine receptors in human amygdala

Recent studies suggested the existence of strychnine-sensitive glycine-receptors in mammalian amygdala. In the present study, we investigated the amino acid concentrations as well as immunocytochemical and pharmacological properties of glycine-receptors in fresh human amygdala tissue obtained from epilepsy surgery.High pressure liquid chromatography revealed a considerable amount of glycine and its precursors and glycine-receptors agonists L-serine and taurine in this tissue. Immunohistochemistry using the monoclonal antibody mAb4a, recognizing an epitope common to all -subunit variants of glycine receptors, displayed a specific labeling at the soma and on proximal dendrites of mostly tripolar, large-sized neurons of irregular distribution and arrangement. To elucidate the pharmacological properties of the glycine-receptors found slices of human amygdala were preloaded with [³H]-choline and superfused. Glycine induced an overflow of [³H]-acetylcholine, which was inhibited by strychnine in a concentration-dependent manner. Furthermore, the glycine-induced release of [³H]-acetylcholine was significantly inhibited by furosemide, indicating glycine-induced actions to be attributed to chloride channels. These actions of glycine were not influenced by MK-801, D-CPPene or bicuculline. Thus, the effects of glycine did not seem to be mediated through NMDA or GABA receptors.These observations indicate that strychnine-sensitive, chloride-conducting glycine receptors, which elicit the release of [³H]-acetylcholine, are present at the soma and on proximal dendrites of neurons in human amygdala. It is hypothesized that glycine may display a regulatory role in amygdaloid functions, probably via cholinergic interneurons.Abbreviations ABC Avidin-biotin-peroxidase complex - ACh Acetylcholine - CI₉₅ 95% Confidence interval - DAB Diaminobenzidine tetrahydrochloride - D-CPPene D-3-(2-carboxypiperazine-4-yl)-1-propenyl-1-phosphonic acid - HPLC High pressure liquid chromatography - GABA -Aminobutyric acid - Gly Glycine - GlyR Glycine receptor - mAb Monoclonal antibody - MK-801 (+)-5-Methyl-10,11-dihydro-5,4-dibenzo[a,d]cyclohepten-5,10-imine maleate - NMDA N-methyl-D-aspartate - NHS Normal horse serum - OPA o-Phthalaldehyde mercaptoethanol - PBS Phosphate buffer saline - TLE Temporal lobe epilepsy     

Behavioral studies on FR115427, a novel selective N-methyl-D-aspartate antagonist

Behavioral and in vitro receptor binding methods were used to evaluate and compare the effects of FR115427 ((+)-1-methyl-1-phenyl-1,2,3,4-tetrahydroisoquinoline hydrochloride) with those of MK801, a non-competitive NMDA antagonist. FR115427 inhibited NMDA-induced convulsions in mice by intracerebroventrical(ICV) and systematic injection. FR115427 was found to be about ten times less potent than MK801. Furthermore, the inhibitory effect of FR115427 and MK801 on NMDA-induced convulsions was evaluated in time course studies in mice. MK801 exhibited a more sustained anticonvulsive activity than FR115427. In addition, PCP-like behaviors were examined in mice after ICV injection of these compounds. At the lowest dose FR115427 significantly increased locomotor activity, although the effect of this compound was about hundred times less potent than that of MK801.At higher dose a more complex pattern of behavior, e.g. head-movement and eventually ataxia was observed. In binding assays with rat brain membranes, FR115427 inhibited the binding of (³H)TCP (IC₅₀=0.249 µM) and (³H)MK801 (IC₅₀=0.312 µM) but did not inhibit the binding of (³H)CPP or (³H)glycine. These results suggest that FR115427 is a novel non-competitive NMDA antagonist that acts on a binding site located within the NMDA receptor associated ion channel.     

谷氨酸损伤大鼠皮层神经元及抑制钙/钙调蛋白依赖性蛋白激酶Ⅱ活性

利用原代培养的大鼠胎鼠皮层神经元 ,采用乳酸脱氢酶 (LDH)测定和32 P参入方法 ,研究谷氨酸 (Glu)对皮层神经元损伤 ,钙 /钙调蛋白依赖性蛋白激酶 (Ca MK )活性的影响及其机理 .Glu(50- 1 0 0 0μmol· L-1)作用 1 0 min,导致皮层神经元Ca MK 活性立即明显下降 ,神经元形态及 LDH释放早期无明显改变 ,2 4 h时 LDH释放显著增加 ,神经元损伤 .N-甲基 - D-天冬氨酸 (NMDA)受体拮抗剂地佐环平 (MK- 80 1 )明显降低 LDH释放 ,保护Ca MK 活性 ,而非 NMDA受体拮抗剂 6,7-二硝基喹口恶啉二酮 (DNQX)无保护作用 .去除胞外 Ca2 +可明显保护 Ca MK 活性 .Ca MK 抑制剂 KN- 62可明显拮抗 Ca MK 活性下降 ,部分保护神经元损伤 .结果提示 ,Glu兴奋毒引起皮层神经元迟发性损伤和 Ca MK 活性早期明显下降 ,主要由 NMDA受体介导和胞外 Ca2 +内流增加有关 .     

Donepezil attenuates excitotoxic damage induced by membrane depolarization of cortical neurons exposed to veratridine

Long-lasting membrane depolarization in cerebral ischemia causes neurotoxicity via increases of intracellular sodium concentration ([Na+]i) and calcium concentration ([Ca2+]i). Donepezil has been shown to exert neuroprotective effects in an oxygen-glucose deprivation model. In the present study, we examined the effect of donepezil on depolarization-induced neuronal cell injury resulting from prolonged opening of Na+ channels with veratridine in rat primary-cultured cortical neurons. Veratridine (10 microM)-induced neuronal cell damage was completely prevented by 0.1 microM tetrodotoxin. Pretreatment with donepezil (0.1-10 microM) for 1 day significantly decreased cell death in a concentration-dependent manner, and a potent NMDA receptor antagonist, dizocilpine (MK801), showed a neuroprotective effect at the concentration of 10 microM. The neuroprotective effect of donepezil was not affected by nicotinic or muscarinic acetylcholine receptor antagonists. We further characterized the neuroprotective properties of donepezil by measuring the effect on [Na+]i and [Ca2+]i in cells stimulated with veratridine. At 0.1-10 microM, donepezil significantly and concentration-dependently reduced the veratridine-induced increase of [Ca2+]i, whereas MK801 had no effect. At 10 microM, donepezil significantly decreased the veratridine-induced increase of [Na+]i. We also measured the effect on veratridine-induced release of the excitatory amino acids, glutamate and glycine. While donepezil decreased the release of glutamate and glycine, MK801 did not. In conclusion, our results indicate that donepezil has neuroprotective activity against depolarization-induced toxicity in rat cortical neurons via inhibition of the rapid influx of sodium and calcium ions, and via decrease of glutamate and glycine release, and also that this depolarization-induced toxicity is mediated by glutamate receptor activation.