Expression of NMDAR1, GluR1, GluR7, and KA1 Glutamate Receptor mRNAs Is Decreased in Frontal Cortex of "Neuroleptic-Free" Schizophrenics: Evidence on Reversible Up-Regulation by Typical Neuroleptics

Abstract: Schizophrenics exhibit abnormalities in many memory-associated functions mediated by the frontal cortex. Glutamate receptors play key roles in learning and memory. Hence, abnormalities in glutamate receptors within the frontal cortex may be associated with schizophrenia. In addition, emerging evidence indicates that glutamate receptors may be involved in the actions of antipsychotic drugs. To test these hypotheses, we measured mRNAs encoding the NMDAR1, GluR1, GluR7, and KA1 subunits of glutamate receptor in the left superior frontal gyrus from 21 elderly schizophrenics with varying histories of antipsychotic drug treatment and nine normal drug-free elderly controls. There were significant negative correlations between NMDAR1, GluR1, GluR7, and KA1 mRNA levels and time without neuroleptic medication before death in schizophrenics, indicating that levels of the glutamate receptor mRNAs decline rapidly after drug withdrawal. Further analysis revealed that in "neuroleptic-free" (>6 months) schizophrenics, levels of NMDAR1, GluR1, GluR7, and KA1 mRNAs were significantly lower than in controls. By contrast, in schizophrenics who were receiving neuroleptics until death, levels of NMDAR1, GluR1, GluR7, and KA1 mRNAs did not differ significantly from controls. These findings indicate that decreased levels of NMDAR1, GluR1, GluR7, and KA1 mRNAs may be present in the frontal cortex of some schizophrenics and that typical neuroleptics may reversibly increase levels of these mRNAs.     

[3H]Paroxetine Binding Is Altered in the Hippocampus but Not the Frontal Cortex or Caudate Nucleus from Subjects with Schizophrenia

Abstract: [³H]Paroxetine binding to particulate membrane from tissue, obtained at autopsy, from the hippocampus, frontal cortex, and caudate nucleus from subjects who had or had not had schizophrenia was measured. The density of [³H]paroxetine binding to membranes from subjects who had or had not had schizophrenia did not differ. Similarly, the affinity of [³H]paroxetine binding in the frontal cortex and caudate nucleus was not different. By contrast, the affinity of [³H]paroxetine binding to hippocampal membrane from subjects who had schizophrenia was significantly lower than the affinity of binding for the nonschizophrenic subjects (0.40 ± 0.06 vs. 0.26 ± 0.02; p < 0.05). As [³H]paroxetine binds to the serotonin transporter, these data suggest that the serotonin transporter is altered in the hippocampus in subjects with schizophrenia.     

Characterisation of Na+-Independent L-[3H]Glutamate Binding Sites in Human Temporal Cortex

The binding of L-[3H]glutamate to membranes from human temporal cortex was studied in the absence of Na+, Ca2+, and Cl- ions. Pharmacological characterisation revealed that approximately 35% of specific binding at 50 nM L-[3H]glutamate was sensitive to a combination of kainate and alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid. The remaining approximately 65% of specific binding was to a single population of sites with a KD of 844 nM and a Bmax of 0.92 pmol/mg protein. The pharmacological characteristics were consistent with an interaction at the N-methyl-D-aspartate subclass of excitatory amino acid receptor. The inclusion of Cl- ions revealed additional glutamate binding; this was sensitive to quisqualate and DL-2-amino-4-phosphonobutyrate, but not to kainate, DL-2-amino-7-phosphonoheptanoate, or alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid.     

Heavy Metals Modulate Glutamatergic System in Human Platelets

Research strategies have been developed to characterize parameters in peripheral tissues that might easily be measured in humans as surrogate markers of damage, dysfunction or interactions involving neural targets of toxicants. The similarities between platelet and neuron may even be clinically important, as a number of biochemical markers show parallel changes in the central nervous system (CNS) and platelets. The purpose of our research was to investigate the effect of Hg²⁺, Pb²⁺ and Cd²⁺ on the [³H]-glutamate binding and [³H]-glutamate uptake in human platelets. The involvement of oxidative stress in the modulation of glutamatergic system induced by heavy metals was also investigated. The present study clearly demonstrates that Hg²⁺, Cd²⁺, and Pb²⁺ inhibited [³H]-glutamate uptake in human platelets. Hg²⁺ inhibited [³H]-glutamate binding, while Cd²⁺ and Pb²⁺ stimulated [³H]-glutamate binding in human platelets. Hg²⁺, Cd²⁺ and Pb²⁺ increased lipid peroxidation levels and reactive oxygen species (ROS) measurement in platelets. The present limited results could suggest that glutamatergic system may be used as a potential biomarker for neurotoxic action of heavy metals in humans.     

Selective Increases in Phosphoinositide Signaling Activity and G Protein Levels in Postmortem Brain from Subjects with Schizophrenia or Alcohol Dependence

Abstract: Comparisons of the activity of the G protein-mediated phosphoinositide signal transduction system and of G protein levels were made in two regions of frontal cortex from eight schizophrenic, alcohol-dependent, and control subjects. G protein-mediated phosphoinositide hydrolysis was measured by stimulating cortical membranes incubated with [³H]phosphatidylinositol with 0.3–10 µM guanosine 5′-O-(3-thio)triphosphate (GTPγS). In frontal cortex areas 8/9, GTPγS-induced phosphoinositide hydrolysis was 50% greater in schizophrenic than control or alcohol-dependent subjects, whereas there were no differences among these groups of subjects in the response to GTPγS in frontal cortex area 10. Agonists for dopaminergic, cholinergic, purinergic, serotonergic, histaminergic, and glutamatergic receptors coupled to the phosphoinositide signaling system increased [³H]phosphatidylinositol hydrolysis in a GTPγS-dependent manner. Responses to most agonists were similar in all three subject groups in both cortical regions, with the largest difference being a 40% greater response to dopaminergic receptor stimulation in frontal cortex 8/9 from schizophrenic subjects. Measurements of the levels of phospholipase C-β, and of α-subunits of G_q, G_o, G_i1, G_i2, and G_s, made by immunoblot analyses revealed no differences among the groups of subjects except for increased Gα_o in schizophrenic subjects and increased Gα_o and Gα_i1 in alcohol-dependent subjects. These results demonstrate that schizophrenia is associated with increased activity of the phosphoinositide signal transduction system and increased levels of Gα_o, whereas the phosphoinositide system was unaltered in alcohol dependence, but Gα_o and Gα_i1 were increased.     

Traumatic Brain Injury-Induced Excitotoxicity Assessed in a Controlled Cortical Impact Model

Using a controlled cortical impact model of traumatic brain injury (TBI) coupled with tissue microdialysis, interstitial concentrations of aspartate and glutamate (together with serine and glutamine) were assessed in rat frontal cortex. Histological analysis indicated that the severity of injury following severe TBI (depth of deformation = 3.5 mm) was approximately twice that occurring following moderate TBI (depth of deformation = 1.5 mm). Both groups demonstrated significant postinjury maximal increases in excitatory amino acid (EAA) concentration, which were proportional to the severity of injury. The mean ± SEM fold increase in dialysate concentrations of aspartate was 38 ± 13 (n = 5) for moderate TBI and 74 ± 12 (n = 5) for severe TBI. Fold increases in glutamate concentrations were 81 ± 26 and 144 ± 23 for moderate and severe TBI, respectively. Although these increases normalized within 20–30 min following moderate TBI, concentrations of aspartate and glutamate took >60 min to normalize after severe TBI. Changes in levels of nontransmitter amino acids were much smaller. Fold increases for serine concentrations were 4.6 ± 0.6 and 7.6 ± 1.7 in moderate and severe TBI, respectively; glutamine concentrations had similar small fold increases (2.6 ± 0.2 and 4.1 ± 0.6, respectively). Calculation of interstitial concentrations following severe TBI indicated that aspartate and glutamate maximally increased to 123 ± 20 and 414 ± 66 μM, respectively. To determine the extent to which such tissue concentrations of EAAs could contribute to the injury seen in TBI, the EAA receptor agonists N-methyl-d - aspartate and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid were slowly injected into rat cortex. Remarkably similar histological injuries were produced by this procedure, supporting the notion that TBI is an excitotoxic injury.     

Increased Concentrations of the Neurotoxin 3-Hydroxykynurenine in the Frontal Cortex of HIV-1-Positive Patients

Abstract: Human immunodeficiency virus (HIV)-1-associated dementia is a frequent consequence of HIV infection and is associated with neuronal deficits. Increased concentrations of the kynurenine pathway metabolites 3-hydroxykynurenine (3-HK) and quinolinic acid (QA) may contribute to this neuronal damage. We measured 3-HK concentrations and the activity of its catabolising enzyme, 3-hydroxykynureninase, in postmortem brain tissue from eight controls and 32 HIV-positive patients, including a group that exhibited dementia. 3-HK concentrations were significantly increased (over threefold) in the HIV-positive group when compared with controls. This increase was greater in those patients with dementia, but it was still apparent in the nondemented cases. 3-Hydroxykynureninase activity was significantly increased in the HIV-infected group compared with the control values. The effect was apparent in both nondementia and dementia cases, although the latter showed a slightly greater increase. The 3-HK content increase is thus unrelated to a reduction in activity of this enzyme and is likely to reflect an overall increase in the kynurenic metabolic pathway. Elevated levels of the neurotoxin 3-HK may contribute to the neuronal deficits underlying HIV-associated dementia.     

Serotonin Metabolism and Release in Frontal Cortex of Rats on a Vitamin E-Deficient Diet

Abstract: Rats were fed a control or vitamin E (all- rac -α-tocopheryl acetate)-deficient diet for 3 or 12 weeks. Serotonin (5-HT), 5-hydroxyindoleacetic acid (5-HIAA), tryptophan, and α-tocopherol concentrations were determined in the frontal cortex using HPLC. α-Tocopherol concentrations fell significantly to 27% of control values at 12 weeks. Tissue 5-HT, 5-HIAA, and tryptophan concentrations were not significantly altered by the vitamin E-deficient diet at either time point. In vivo microdialysis revealed normal basal and K⁺-stimulated concentrations of 5-HT and 5-HIAA, but extracellular concentrations of tryptophan were significantly decreased after 3 weeks on the vitamin E-deficient diet, which resulted in an increase in the tissue/extracellular ratio and suggested a change in compartmentation. However, after 12 weeks on the deficient diet these values had returned to normal. Results in general indicate that a prolonged and substantial depletion of brain vitamin E can occur without major disturbance of serotonergic function.     

Characterisation, Density, and Distribution of Kainate Receptors in Normal and Alzheimer''s Diseased Human Brain

The specific binding of [3H]kainic acid was investigated in membrane preparations from human parietal cortex obtained postmortem. Saturation studies revealed that binding occurred to a single population of sites with a KD of 15 nM and a Bmax of 110 fmol/mg of protein. The kinetically determined dissociation constant for these sites agreed well with that obtained from saturation analyses. Pharmacological characterisation of these sites gave a profile consistent with those reported for kainate receptor sites in animal brain. The integrity of kainate receptors was studied in several brain regions from six patients who had died of Alzheimer's disease and from six closely matched control subjects. No change in either the affinity or the number of kainate receptors was seen in any of the regions studied, despite the loss of neocortical and hippocampal glutamatergic terminals in the Alzheimer's diseased brains, as previously reported.     

Glutamatergic Regulation of Basal and Stimulus-Activated Dopamine Release in the Prefrontal Cortex

Abstract: The present study was undertaken to determine whether basal and stimulus-activated dopamine release in the prefrontal cortex (PFC) is regulated by glutamatergic afferents to the PFC or the ventral tegmental area (VTA), the primary source of dopamine neurons that innervate the rodent PFC. In awake rats, blockade of NMDA or α-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) receptors in the VTA, or blockade of AMPA receptors in the PFC, profoundly reduced dopamine release in the PFC, suggesting that the basal output of dopamine neurons projecting to the PFC is under a tonic excitatory control of NMDA and AMPA receptors in the VTA, and AMPA receptors in the PFC. Consistent with previous reports, blockade of cortical NMDA receptors increased dopamine release, suggesting that NMDA receptors in the PFC exert a tonic inhibitory control on dopamine release. Blockade of NMDA or AMPA receptors in the VTA as well as blockade of AMPA receptors in the PFC reduced the dopaminergic response to mild handling, suggesting that activation of glutamate neurotransmission also regulates stimulus-induced increase of dopamine release in the PFC. In the context of brain disorders that may involve cortical dopamine dysfunction, the present findings suggest that abnormal basal or stimulus-activated dopamine neurotransmission in the PFC may be secondary to glutamatergic dysregulation.     

Serotonergic Regulation of Acetylcholine Release in Rat Frontal Cortex

Abstract: The extent to which serotonin regulates the activity of cortically projecting cholinergic neurons was studied using in vivo microdialysis to monitor interstitial concentrations of acetylcholine in the frontal cortex of freely moving rats. Systemic administration of the serotonin release-inducing agent fenfluramine (3 or 10 mg/kg, i.p.) increased acetylcholine release by 110–130%. The fenfluramine-induced increase in acetylcholine release was significantly attenuated by pretreatment with the selective serotonin uptake inhibitor fluoxetine (10 mg/kg, i.p.). Pretreatment with the selective dopamine D₁ receptor antagonist SCH-23390 (0.3 mg/kg, s.c.) failed to prevent the fenfluramine-induced increase in acetylcholine release. In contrast, the serotonin 5-HT_2A receptor antagonist ketanserin (5 mg/kg, i.p.) blocked fenfluramine-induced increases in acetylcholine release. In contrast to previous studies that have concluded that serotonin has inhibitory actions on cortical acetylcholine release, the present results indicate that fenfluramine increases cortical acetylcholine release in vivo by its ability to enhance serotonin transmission and that serotonin produces these effects at least in part via actions at serotonin 5-HT_2A receptors.     

Characteristics of [3H]GBR 12935 Binding in the Human and Rat Frontal Cortex

Binding characteristics of the selective dopamine uptake inhibitor [3H]GBR 12935 have been described for the striatum but not for the frontal cortex. We have developed assay conditions for quantifying [3H]GBR 12935 binding in the frontal cortex. In both the rat and human frontal cortex, the assay required four times more tissue (8 mg/ml) than in the striatum (2 mg/ml). [3H]GBR 12935 binding in the frontal is complex, as it involves multiple binding sites. The high-affinity binding site is sodium dependent and is inhibited by sodium. In human but not in rat frontal cortex, addition of K+ reversed the sodium inhibition. The pharmacological profile of the high-affinity [3H]GBR 12935 binding site is consistent with that of the dopamine transporter, because drugs with the most selective dopamine reuptake blocking activities are the most potent displacers of [3H]GBR 12935 binding. There is a positive correlation between the rat and human inhibitory constants, a finding indicating that there are similar pharmacological profiles across at least these two species. Rats with a 6-hydroxydopamine lesion had a 47% decrease in number of [3H]GBR 12935 binding sites, a result indicating that at least a portion of these sites had been on presynaptic dopamine terminals.     

谷氨酸及γ-氨基丁酸在氯胺酮致大鼠精神分裂样表现中的变化

目的:观察大鼠前额皮层谷氨酸(Glu)及γ-氨基丁酸(GABA)在氯胺酮致精神分裂样表现中的变化。方法:雄性Wistar大鼠32只随机分为生理盐水组(S组,n=16)和氯胺酮组(K组,n=16)。腹腔注射生理盐水或氯胺酮30 mg/kg(容积1 mL),一天一次,连续5天,最后一次给药后0.5 h及2 h分别通过敞箱实验观察大鼠自主活动,并记录刻板行为评分。行为学测试后,取大鼠前额皮层,检测Glu及GABA含量。结果:与S组比较,K组大鼠给药后0.5 h自主活动增强、刻板行为评分增高(P0.05),符合精神分裂症大鼠表现;给药后2 h行为学评分则无显著差异(P0.05);给药后0.5 h及2 h大鼠前额皮层Glu水平均增加、GABA水平均下降(P0.05)。与氯胺酮给药后0.5 h组相比,给药后2 h Glu水平下降(P0.05)、GABA水平则无显著差异(P0.05)。结论:氯胺酮致精神分裂样表现可能与大鼠前额皮层Glu增加及GABA减少有关。     

Synergistic Regulation of Glutamatergic Transmission by Serotonin and Norepinephrine Reuptake Inhibitors in Prefrontal Cortical Neurons

The monoamine system in the prefrontal cortex has been implicated in various mental disorders and has been the major target of anxiolytics and antidepressants. Clinical studies show that serotonin and norepinephrine reuptake inhibitors (SNRIs) produce better therapeutic effects than single selective reuptake inhibitors, but the underlying mechanisms are largely unknown. Here, we found that low dose SNRIs, by acting on 5-HT_1A and α₂-adrenergic receptors, synergistically reduced AMPA receptor (AMPAR)-mediated excitatory postsynaptic currents and AMPAR surface expression in prefrontal cortex pyramidal neurons via a mechanism involving Rab5/dynamin-mediated endocytosis of AMPARs. The synergistic effect of SNRIs on AMPARs was blocked by inhibition of activator of G protein signaling 3, a G protein modulator that prevents reassociation of G_i protein α subunit and prolongs the βγ-mediated signaling pathway. Moreover, the depression of AMPAR-mediated excitatory postsynaptic currents by SNRIs required p38 kinase activity, which was increased by 5-HT_1A and α₂-adrenergic receptor co-activation in an activator of G protein signaling 3-dependent manner. These results have revealed a potential mechanism for the synergy between the serotonin and norepinephrine systems in the regulation of glutamatergic transmission in cortical neurons.     

左西孟旦治疗心脏术后左心室收缩功能低下

目的:明确左西孟旦治疗心脏术后左心室收缩功能低下的效果。方法:随即抽取2009年6月至今手术治疗后左室射血分数小于35%的患者,分为治疗组和对照组,各25例,给与不同治疗方案。比较两组患者治疗后效果;呼吸状况和全身状况;再次气管插管例数和监护室滞留时间;治疗后左心室射血分数(LVEF)、小轴短缩率(LVFS)。结果:治疗组和对照组分别有3例和5例因心力衰竭死亡。两组患者治疗后再次气管插管例数无统计学差异。与对照组比较,治疗组患者监护室滞留时间短、呼吸状况和全身状况较好(P<0.05),LVEF和LVFS较高有统计学意义(P<0.05)。结论:左西孟旦治疗心脏术后左心室收缩功能低下安全有效,缓解症状明显。     

Neuropeptide Y in Frontal Cortex Is Not Altered in Major Depression

Abstract: Previously, we reported a modest but significant reduction in the concentration of neuropeptide Y in frontal cortices from victims of suicide relative to age-matched natural or accidental death control subjects. The reduction in neuropeptide Y appeared to be greatest in a subgroup of victims of suicide for which there was indirect evidence of histories of depression. We pursued these initial findings in the present study by measuring neuropeptide Y concentrations in frontal cortices from natural or accidental death control subjects and from suicide victims in whom a firm diagnosis of major depression was established by psychiatric autopsy. Because several subjects with major depression had a comorbid diagnosis of alcoholism, a group of victims of suicide that had an Axis I diagnosis of alcohol dependence was also studied. No significant differences in neuropeptide Y concentrations were observed between control subjects and victims of suicide with major depression or victims of suicide with alcohol dependence. These findings do not support a role for neuropeptide Y in major depression.     

The Prefrontal Cortex Regulates the Basal Release of Dopamine in the Limbic Striatum: An Effect Mediated by Ventral Tegmental Area

Abstract: The present study examined whether the prefrontal cortex (PFC) exerts a tonic control over the basal release of dopamine in the limbic striatum and whether this control is mediated by glutamatergic afferents to the dopamine cell body or terminal regions. Using intracerebral microdialysis in freely moving rats, it was demonstrated that application of tetrodotoxin in the contralateral PFC significantly decreased the release of dopamine in the medial striatum. Conversely, blockade of the tonic inhibitory GABAergic input in the PFC with bicuculline increased the release of dopamine in the medial striatum. Application of excitatory amino acid receptor antagonists into the striatum, while bicuculline was perfused in the PFC, did not affect the bicuculline-evoked dopamine increase in the striatum. However, infusion of tetrodotoxin or excitatory amino acid receptor antagonists into the ventral tegmental area, a region containing dopamine cell bodies that project to the medial striatum, blocked the stimulation of striatal dopamine release induced by infusion of bicuculline into the PFC. These data demonstrate that the basal output of dopamine terminals in the medial striatum is under a tonic excitatory control of the PFC. Furthermore, this control occurs primarily through glutamatergic projections to the dopamine cell body area rather than the terminal regions.     

Stress- and Yohimbine-Induced Release of Cholecystokinin in the Frontal Cortex of the Freely Moving Rat: Prevention by Diazepam but Not Ondansetron

Abstract: The in vivo release of cholecystokinin (CCK)-like material (CCKLM) was measured in the frontal cortex of freely moving rats using the microdialysis technique combined with a sensitive radioimmunoassay. Local perfusion of K⁺ (100 m M )-enriched artificial CSF resulted in a 10-fold increase in CCKLM outflow, as compared with that occurring under basal resting (K⁺ = 3.0 m M ) conditions, and this effect could be completely prevented by removal of Ca²⁺ in the perfusing fluid. Chromatographic analyses demonstrated that CCK-8S contributed to 70% of CCKLM. Stressful stimuli such as a 2-min exposure to diethyl ether and a 30-min restraint produced a marked but transient increase in cortical CCKLM release. In addition, anxiety-like behavior induced by the systemic administration of yohimbine (5 mg/kg i.p.) was associated with a long-lasting enhancement in the peptide outflow. Pretreatment with the potent anxiolytic drug diazepam (5 mg/kg i.p., 5 min before each condition), which exerted no effect on its own, completely prevented CCKLM overflow due to diethyl ether, restraint, or yohimbine administration. In contrast, neither the systemic injection (0.1 mg/kg i.p.) nor the local application (100 µ M through the microdialysis probe) of the serotonin 5-HT₃ antagonist ondansetron affected the increased release of CCKLM in rats restrained for 30 min or treated with yohimbine. These results indicate that cortical CCKergic neurotransmission is increased during stress or anxiety-like behavior in rats. Prevention of this effect by diazepam suggests that an inhibitory influence of benzodiazepines on cortical CCKergic neurons might participate in the anxiolytic action of these drugs.     

Reduced Proteins in Temporal Cortex in Alzheimer''s Disease: An Electrophoretic Study

Cytoplasmic and pellet fractions from post-mortem temporal cortex from eight cases of neuropathologically confirmed Alzheimer's disease, one case of cerebrovascular dementia, and five controls were examined by sodium dodecylsulphate-polyacrylamide gel electrophoresis. No differences were observed in the cytoplasmic proteins from the five controls and the case of cerebrovascular dementia. In five cases of Alzheimer's disease with neurone loss, there was a major loss of a cytoplasmic 55,000-dalton protein identified as tubulin and variable reductions in cytoplasmic proteins of molecular weights of 28,000, 30,000, 92,000, and 200,000 daltons. Three cases of Alzheimer's disease had no detectable neurone loss; two of these cases had protein patterns indistinguishable from the controls and one showed some reduction in soluble tubulin only. These results indicate that decreases of particular proteins in the temporal cortex in Alzheimer's disease may be associated with neurone loss.