Glutamate levels in the medial prefrontal cortex of healthy pregnant women compared to non-pregnant controls.

Very little is known about maternal cerebral changes during pregnancy. Since there is an increased risk for major depression during pregnancy and postpartum, it is important to understand the structural and neurochemical changes that occur in the brain during pregnancy. Using proton magnetic resonance spectroscopy (1H-MRS) (3 T field strength), glutamate (Glu) levels were measured in the medial prefrontal cortex (MPFC) of 21 healthy gravid subjects 2-3 weeks before their due date (6.74 ± 1.39), and in 14 non-pregnant healthy controls during their follicular phase (8.53 ± 1.55). Water quantified MPFC Glu levels were decreased in pregnant women (p < 0.01). We also observed a 13.9% decrease in percentage grey matter (%GM) (p < 0.01) in our MPFC voxel. As Glu is mostly found in GM, we repeated the statistical analysis after adjustment for %GM and found that the difference in Glu levels was no longer statistically significant when adjusted for %GM (p = 0.10). This investigation is the only systematic direct investigation of brain tissue composition and Glu levels in pregnant women. The main finding of this investigation is the decreased %GM in healthy pregnant women compared to non-pregnant women. These findings of decreased %GM in pregnancy may be responsible for the frequent complaints by pregnant women of cognitive difficulties also described as pregnesia.

Disability progression in multiple sclerosis is associated with plasma neuroactive steroid profile.

BACKGROUND: Neuroactive steroids (NASs) exert multiple biological effects on development and inflammation. The effects of NASs on disease progression in multiple sclerosis (MS) are uncertain, prompting analyses of NAS profiles during the transition from clinically isolated syndrome (CIS) to relapsing-remitting (RR) MS. METHODS: Subjects with CIS or RRMS and healthy controls (HCs) were recruited; demographic and clinical data as well as disability scores measured by the Expanded Disability Status Scale (EDSS) were recorded. Matched plasma NAS and amino acid (AA) concentrations were measured. RESULTS: HC (n = 17), CIS (n = 31), and RRMS (n = 33) groups showed similar ages and sex distribution although disability scores were higher in the RRMS group. The conversion rate of CIS to RRMS group was 51.6% (n = 16) during a mean follow-up period of 1.85 years. The RRMS group showed significantly higher mean allopregnanolone, aspartate, and taurine concentrations with lower epiallopregnanolone concentrations than CIS patients, and higher L-serine-O-phosphate and lower alanine, arginine, and glutamine concentrations than the HC group. Among CIS and RRMS groups, multivariate hierarchical regressions revealed that higher concentrations of plasma tetrahydrodeoxycorticosterone (THDOC) may predict disability worsening. CONCLUSIONS: RRMS and CIS patients exhibited differing concentrations of both NASs and AAs in plasma while both THDOC and pregnanolone might serve as biomarkers of disability worsening.

Metrics of progress in the understanding and management of threats to Australian birds.

Although evidence-based approaches have become commonplace for determining the success of conservation measures for the management of threatened taxa, there are no standard metrics for assessing progress in research or management. We developed 5 metrics to meet this need for threatened taxa and to quantify the need for further action and effective alleviation of threats. These metrics (research need, research achievement, management need, management achievement, and percent threat reduction) can be aggregated to examine trends for an individual taxon or for threats across multiple taxa. We tested the utility of these metrics by applying them to Australian threatened birds, which appears to be the first time that progress in research and management of threats has been assessed for all threatened taxa in a faunal group at a continental scale. Some research has been conducted on nearly three-quarters of known threats to taxa, and there is a clear understanding of how to alleviate nearly half of the threats with the highest impact. Some management has been attempted on nearly half the threats. Management outcomes ranged from successful trials to complete mitigation of the threat, including for one-third of high-impact threats. Progress in both research and management tended to be greater for taxa that were monitored or occurred on oceanic islands. Predation by cats had the highest potential threat score. However, there has been some success reducing the impact of cat predation, so climate change (particularly drought), now poses the greatest threat to Australian threatened birds. Our results demonstrate the potential for the proposed metrics to encapsulate the major trends in research and management of both threats and threatened taxa and provide a basis for international comparisons of evidence-based conservation science.

Medidas de Progreso en el Entendimiento y el Manejo de las Amenazas que Enfrentan las Aves Australianas Resumen Aunque los métodos basados en evidencias se han vuelto muy comunes para la determinación del éxito de las medidas de conservación del manejo de los taxones amenazados, hoy en día no existen medidas estandarizadas para la evaluación del progreso de la investigación o el manejo. Desarrollamos cinco medidas para cumplir con esta necesidad que tienen los taxones amenazados y para cuantificar la necesidad de una mayor acción y un alivio efectivo de las amenazas. Estas medidas (falta de investigación, éxito de la investigación, falta de manejo, éxito del manejo y porcentaje de reducción de amenazas) pueden agregarse para examinar las tendencias de un taxón individual o las tendencias de las amenazas para múltiples taxones. Probamos la utilidad de estas medidas por medio de su aplicación en aves australianas amenazadas, que parece ser la primera vez que se evalúa el progreso en la investigación y en el manejo de amenazas para el caso de varios taxones amenazados dentro de un grupo faunístico a escala continental. Se ha realizado algún tipo de investigación sobre casi tres cuartas partes de las amenazas conocidas para los taxones, y hay un claro entendimiento de cómo aliviar casi la mitad de las amenazas con el impacto más alto. Se ha intentado algún tipo de manejo con casi la mitad de las amenazas. Los resultados del manejo variaron desde ensayos exitosos hasta la mitigación completa de la amenaza, incluso para un tercio de las amenazas de alto impacto. Tanto el progreso en la investigación como en el manejo tendió a ser mayor para los taxones que estaban siendo monitoreados, o que ocurrían en islas oceánicas. La depredación por gatos tuvo el puntaje más como amenaza potencial. Sin embargo, ha habido poco de éxito en la reducción del impacto de la depredación por gatos, así que ahora el cambio climático (particularmente la sequía) es la mayor amenaza para las aves amenazadas en Australia. Nuestros resultados demuestran el potencial que tienen las medidas propuestas de encapsular las tendencias más importantes en la investigación y en el manejo tanto de las amenazas como de los taxones amenazados y de proporcionar una base para comparaciones internacionales de la ciencia de la conservación basada en evidencias.

Dopamine cross-sensitization between psychostimulant drugs and stress in healthy male volunteers.

Dysregulation of the stress response system is a potential etiological factor in the development of and relapse to multiple neuropsychiatric disorders. Previously we reported that repeated intermittent d-amphetamine administration can lead to progressively greater dopamine release, thereby providing evidence of drug-induced neurochemical sensitization. Here, we test the hypothesis that repeated exposure to d-amphetamine increases dopaminergic responses to stress; that is, produces cross-sensitization. Using positron emission tomography, we measured in 17 healthy male volunteers (mean ± s.d. = 22.1 ± 3.4 years) [(11)C]raclopride binding responses to a validated psychosocial stress task before and 2 weeks after a regimen of repeated d-amphetamine (3 × 0.3 mg kg(-1), by mouth; n = 8) or placebo (3 × lactose, by mouth; n = 9). Mood and physiological measurements were recorded throughout each session. Before the d-amphetamine regimen, exposure to the stress task increased behavioral and physiological indices of stress (anxiety, heart rate, cortisol, all P ⩽ 0.05). Following the d-amphetamine regimen, the stress-induced cortisol responses were augmented (P < 0.04), and voxel-based analyses showed larger stress-induced decreases in [(11)C]raclopride non-displaceable binding potential across the striatum. In the placebo group, re-exposure to stress led to smaller clusters of decreased [(11)C]raclopride binding, primarily in the sensorimotor striatum (P < 0.05). Together, this study provides evidence for drug × stress cross-sensitization; moreover, random exposure to stimulants and/or stress cumulatively, while enhancing dopamine release in striatal areas, may contribute to a lowered set point for psychopathologies in which altered dopamine neurotransmission is invoked.

In vitro validation of effects of BDNF-expressing mesenchymal stem cells on neurodegeneration in primary cultured neurons of APP/PS1 mice.

Alzheimer's disease (AD), the most common type of dementia, is characterized by the presence of senile plaques, neurofibrillary tangles, and neuronal loss in defined regions of the brain including the hippocampus and cortex. Transplantation of bone marrow-derived mesenchymal stem cells (BM-MSCs) offers a safe and potentially effective tool for treating neurodegenerative disorders. However, the therapeutic effects of BM-MSCs on AD pathology remain unclear and their mechanisms at cellular and molecular levels still need to be addressed. In this study, we developed a unique neuronal culture made from 5xFAD mouse, an APP/PS1 transgenic mouse model (FAD neurons) to investigate progressive neurodegeneration associated with AD pathology and efficacy of brain-derived neurotrophic factor expressing-MSCs (BDNF-MSCs). Analyses of the expression of brain-derived neurotrophic factor (BDNF), synaptic markers and survival/apoptotic signals indicate that pathological features of cultured neurons made from these mice accurately mimic AD pathology, suggesting that our protocol provided a valid in vitro model of AD. We also demonstrated amelioration of AD pathology by MSCs in vitro when these FAD neurons were co-cultured with MSCs, a paradigm that mimics the in vivo environment of post-transplantation of MSCs into damaged regions of brains. To overcome failed delivery of BDNF to the brain and to enhance MSCs releasing BDNF effect, we created BDNF-MSCs and found that MSCs protection was enhanced by BDNF-MSCs. This protection was abolished by BDNF-blocking peptides, suggesting that BDNF supply from BDNF-MSCs was enough to prevent AD pathology.

GABA transport and neuroinflammation are coupled in multiple sclerosis: regulation of the GABA transporter-2 by ganaxolone.

Interactions between neurotransmitters and the immune system represent new prospects for understanding neuroinflammation and associated neurological disease. GABA is the chief inhibitory neurotransmitter but its actions on immune pathways in the brain are unclear. In the present study, we investigated GABAergic transport in conjunction with neuroinflammation in models of multiple sclerosis (MS). Protein and mRNA levels of γ-amino butyric acid transporter 2 (GAT-2) were examined in cerebral white matter from MS and control (Non-MS) patients, in cultured human macrophages, microglia and astrocytes, and in spinal cords from mice with and without experimental autoimmune encephalomyelitis (EAE) using western blotting, immunocytochemistry and quantitative real-time polymerase chain reaction (qRT-PCR). GABA levels were measured by HPLC. The GAT-2's expression was increased in MS patients' (n=6) white matter, particularly in macrophage lineage cells, compared to Non-MS patients (n=6) (p<0.05). Interferon-γ (IFN-γ) stimulation of human macrophage lineage cells induced GAT-2 expression and reduced extracellular GABA levels (p<0.05) but soluble GABA treatment suppressed HLA-DRα, GAT-2 and XBP-1/s expression in stimulated macrophage lineage cells (p<0.05). Similarly, the synthetic allopregnanolone analog, ganaxolone (GNX), repressed GAT-2, JAK-1 and STAT-1 expression in activated macrophage lineage cells (p<0.05). In vivo GNX treatment reduced Gat-2, Cd3ε, MhcII, and Xbp-1/s expression in spinal cords following EAE induction (p<0.05), which was correlated with improved neurobehavioral outcomes and reduced neuroinflammation, demyelination and axonal injury. These findings highlight altered GABAergic transport through GAT-2 induction during neuroinflammation. GABA transport and neuroinflammation are closely coupled but regulated by GNX, pointing to GABAergic pathways as therapeutic targets in neuroinflammatory diseases.

Metabolomic profiling in multiple sclerosis: insights into biomarkers and pathogenesis.

Metabolomics enables the provision of sensitive bio-markers of disease. We performed 800 MHz (1)H-nuclear magnetic resonance (NMR) spectroscopic analyses of cerebrospinal fluid (CSF) specimens to identify biomarkers of multiple sclerosis (MS), yielding reproducible detection of 15 metabolites from MS (n=15) and non-MS (n=17) patients. Mean levels of choline, myo-inositol and threonate were increased, whereas 3-hydroxybutyrate, citrate, phenylalanine, 2-hydroxyisovalerate and mannose were decreased in MS-derived CSF (p<0.05), suggesting alterations to energy and phospholipid metabolism. Multivariate hierarchal cluster analysis indicated a high correlation within the metabolite profiles, significantly clustering samples into the two clinical groups, which was corroborated using principal components analysis. CSF metabolomics have the capacity to yield quantitative biomarkers and insights into the pathogenesis of MS.

Activity and metabolism-related Ca2+ and mitochondrial dynamics in co-cultured human fetal cortical neurons and astrocytes.

Neurons and neighboring astrocytic glia are mostly studied in nervous tissues from rodents whereas less is known on their properties and interactions in the human brain. Here, confocal/multiphoton fluorescence imaging for several hours revealed that co-cultured fetal human cortical neurons and astrocytes show pronounced spontaneous rises of cytosolic Ca(2+) which last for up to several minutes without concomitant changes in either movements or membrane potential of mitochondria. Similar Ca(2+) rises were evoked mainly in neurons by bath-applied glutamate or γ-aminobutyric acid (GABA) acting via N-methyl-d-aspartate (NMDA)+AMPA/Kainate and GABAA receptors, respectively. Predominantly in astrocytes, Ca(2+) baseline was elevated by adenosine diphosphate (ADP) and adenosine triphosphate (ATP) acting via P2Y1 and P2X7 receptors, likely causing the release of glutamate and glutamine. Mainly astrocytes responded to histamine, whereas the activation of muscarinic acetylcholine (ACh) receptors raised Ca(2+) in both cell types. Evoked neuronal and astrocytic Ca(2+) rises could last for several minutes without affecting mitochondrial movements or membrane potential. In contrast, reversible depolarization of mitochondrial membrane potential accompanied neuronal Ca(2+) rises induced by cyanide-evoked chemical anoxia or the uncoupling of mitochondrial respiration with carbonyl-cyanide-4-(trifluoromethoxy)-phenylhydrazone (FCCP). During such metabolic perturbation, mitochondrial depolarization also occurred in astrocytes, whereas Ca(2+) was largely unaffected. In summary, fetal human cortical neurons and astrocytes show distinct patterns of neuro/glio-transmitter- and metabolically-evoked Ca(2+) rises and possess active mitochondria. One aspect of our discussion deals with the question of whether the functional mitochondria contribute to cellular Ca(2+) homeostasis that seems to be already well-developed in fetal human cortical brain cells.

Fluoxetine and citalopram decrease microglial release of glutamate and D-serine to promote cortical neuronal viability following ischemic insult.

Depression is one of the most common disorders appearing following a stroke, and is also a major factor limiting recovery and rehabilitation in stroke patients. Antidepressants are the most common prescribed treatment for depression and have shown to have anti-inflammatory properties within the central nervous system (CNS). The major source of pro-inflammatory factors within the CNS is from activated microglia, the innate immune cells of the CNS. Antidepressants have been shown to promote midbrain and hippocampal neuronal survival following an ischemic insult and this survival is mediated through the anti-inflammatory effects on microglia, but the effects on cortical neuronal survival after this insult have yet to be investigated. The present study aimed to test and compare antidepressants from three distinct classes (tricyclics, monoamine oxidase inhibitors, and selective serotonin-reuptake inhibitors [SSRIs]) on the release of inflammatory factors and amino acids from activated microglia and whether altering this release could affect cortical neuronal viability after an ischemic insult. Primary microglia were treated with 1 µg/ml LPS and/or 10 µM antidepressants, and the various factors released into medium were assayed. Co-cultures consisting of microglia and primary cortical neurons were used to assess the effects of antidepressant-treated activated microglia on the viability of ischemic injured neurons. Of the antidepressants tested, most decreased the release of the proinflammatory factors nitric oxide, tumor necrosis factor-alpha, and interleukin 1-beta from activated microglia. Fluoxetine and citalopram, the SSRIs, decreased the release of the amino acids glutamate and d-serine from LPS-activated microglia. oxygen-glucose deprived (OGD) cortical neurons cocultured with LPS-activated microglia pre-treated with fluoxetine and citalopram showed greater survival compared to injured neurons co-cultured with untreated activated microglia. Microglial release of glutamate and d-serine was shown to be the most important factor mediating neuronal survival following antagonism studies. To our knowledge, our results demonstrate for the first time that fluoxetine and citalopram decrease the release of glutamate and d-serine from LPS-activated microglia and this causes an increase in the survival of OGD-injured cortical neurons after co-culture.

Inhibition of ß-amyloid1-42 internalization attenuates neuronal death by stabilizing the endosomal-lysosomal system in rat cortical cultured neurons.

A number of recent studies have indicated that accumulation of ß amyloid (Aß) peptides within neurons is an early event which may trigger degeneration of neurons and subsequent development of Alzheimer's disease (AD) pathology. However, very little is known about the internalization and/or subcellular sites involved in trafficking of Aß peptides into the neurons that are vulnerable in AD pathology. To address this issue we evaluated internalization of fluoroscein conjugated Aß1-42 (FAß1-42) and subsequent alteration of endosomal-lysosomal (EL) markers such as cathepsin D, Rab5 and Rab7 in rat cortical cultured neurons. It is evident from our results that internalization of FAß1-42, which occurred in a dose- and time-dependent manner, triggered degeneration of neurons along with increased levels and/or altered distribution of cathepsin D, Rab5 and Rab7. Our results further revealed that FAß1-42 internalization was attenuated by phenylarsine oxide (a general inhibitor of endocytosis) and sucrose (an inhibitor of clathrin-mediated endocytosis) but not by antagonists of N-methyl-d-aspartate (NMDA) glutamate receptors. Additionally, inhibition of FAß1-42 endocytosis not only protected neurons against toxicity but also reversed the altered levels/distributions of EL markers. These results, taken together, suggest that internalization of exogenous Aß1-42, which is partly mediated via a clathrin-dependent process, can lead to degeneration of neurons, possibly by activating the EL system. Inhibition of FAß endocytosis attenuated toxicity, thus suggesting a potential strategy for preventing loss of neurons in AD pathology.

Leu27 insulin-like growth factor-II, an insulin-like growth factor-II analog, attenuates depolarization-evoked GABA release from adult rat hippocampal and cortical slices.

Accumulated evidence suggests that the single transmembrane domain insulin-like growth factor-II/mannose 6-phosphate receptor (IGF-II/M6P or IGF-II receptor) plays an important role in the intracellular trafficking of lysosomal enzymes and endocytosis-mediated degradation of insulin like growth factor (IGF-II). However, the role of this receptor in signal transduction following IGF-II binding remains controversial. In the present study, we revealed that Leu(27)IGF-II, an analog which binds preferentially to the IGF-II receptor, can attenuate K(+)-as well as veratridine-evoked GABA release from the adult rat hippocampal formation. Tetrodotoxin failed to alter the effects of Leu(27)IGF-II on GABA release, thus suggesting the lack of involvement of voltage-dependent Na(+) channels. Interestingly, the effect is found to be sensitive to pertussis toxin (PTX), indicating the possible involvement of a Gi/o protein-dependent pathway in mediating the release of GABA from the hippocampal slices. Additionally, Leu(27)IGF-II was found to attenuate GABA release from frontal cortex but not from striatum. These results, together with the evidence that IGF-II receptors are localized on GABAergic neurons, raised the possibility that this receptor, apart from mediating intracellular trafficking, may also be involved in the regulation of endogenous GABA release by acting directly on GABAergic terminals.

An update on the role of glutamate in the pathophysiology of depression.

OBJECTIVE: To review the literature on the involvement of glutamate (Glu), including its interactions with other neurochemical systems, in the pathophysiology of depression. METHOD: A MEDLINE search using the terms glutamate, depression and major depressive disorder, was performed. RESULTS: Alterations in proteins involved in glutamatergic signalling are implicated in variations in behaviour in animal models of depression. Drugs acting at Glu receptors appear to have antidepressant-like effects in these models, and traditional antidepressant pharmacotherapies act on the glutamatergic system. Recent evidence from genetic studies and in vivo spectroscopy also correlate glutamatergic dysfunction with depression. Trials of N-methyl-d-aspartate receptor antagonists in humans have provided mixed results. CONCLUSION: A growing body of evidence indicates that the glutamatergic system is involved in the pathophysiology of depression, and may represent a target for intervention.

Genetic loss of D-amino acid oxidase activity reverses schizophrenia-like phenotypes in mice.

Reduced function of the N-methyl-d-aspartate receptor (NMDAR) has been implicated in the pathophysiology of schizophrenia. The NMDAR contains a glycine binding site in its NR1 subunit that may be a useful target for the treatment of schizophrenia. In this study, we assessed the therapeutic potential of long-term increases in the brain levels of the endogenous NMDAR glycine site agonist D-serine, through the genetic inactivation of its catabolic enzyme D-amino acid oxidase (DAO) in mice. The effects of eliminating DAO function were investigated in mice that display schizophrenia-related behavioral deficits due to a mutation (Grin 1(D481N)) in the NR1 subunit that results in a reduction in NMDAR glycine affinity. Grin 1(D481N) mice show deficits in sociability, prolonged latent inhibition, enhanced startle reactivity and impaired spatial memory. The hypofunctional Dao 1(G181R) mutation elevated brain levels of D-serine, but alone it did not affect performance in the behavioral measures. Compared to animals with only the Grin 1(D481N) mutation, mice with both the Dao1(G181R) and Grin 1(D481N) mutations displayed an improvement in social approach and spatial memory retention, as well as a reversal of abnormally persistent latent inhibition and a partial normalization of startle responses. Thus, an increased level of D-serine resulting from decreased catalysis corrected the performance of mice with deficient NMDAR glycine site activation in behavioral tasks relevant to the negative and cognitive symptoms of schizophrenia. Diminished DAO activity and elevations in D-serine may serve as an effective therapeutic intervention for the treatment of psychiatric symptoms.

Dehydroepiandrosterone sulphate improves cholestasis-associated fatigue in bile duct ligated rats.

Fatigue is a common debilitating symptom in patients with primary biliary cirrhosis (PBC). The mechanism of fatigue is still poorly understood. However, it has been reported that levels of the steroid dehydroepiandrosterone sulphate (DHEAS) are reduced in plasma of patients with PBC, and substitutive therapy has been suggested to improve fatigue symptoms experienced during the course of this disease. In this study, we tested the effect of DHEAS on whole body fatigue in rats following bile duct ligation (BDL). Fatigue was estimated by the time spent on an electrified grid as a result of falling off a treadmill and by performance of rats on an infrared beam monitor which allows the assessment of travelled distance and stereotypic movement activities. On day 5 after BDL surgery, cholestatic rats exhibited increased whole body fatigue as reflected by significantly increased time spent on the electrified grid, reduced travelled distance and reduced stereotypic movements. Administration of 5 mg kg(-1) of DHEAS to BDL rats for three consecutive days significantly normalized their behaviour. Fatigue scores were also found to be reduced in cirrhotic rats 4 weeks after BDL surgery, and DHEAS treatment for 3 days reduced fatigue scores at this stage. Dehydroepiandrosterone sulphate treatment was sufficient to increase brain levels of DHEAS in the BDL rats in a manner that is significantly and highly correlated with those of plasma DHEAS and brain dehydroepiandrosterone (DHEA). Substitutive therapies with DHEAS or DHEA could represent novel approaches in the management of fatigue due to cholestasis-induced liver failure.

Memantine protects rat cortical cultured neurons against beta-amyloid-induced toxicity by attenuating tau phosphorylation.

It has been suggested that accumulation of beta-amyloid (Abeta) peptide triggers neurodegeneration, at least in part, via glutamate-mediated excitotoxicity in Alzheimer's disease (AD) brain. This is supported by observations that toxicity induced by Abeta peptide in cultured neurons and in adult rat brain is known to be mediated by activation of glutamatergic N-methyl-d-aspartate (NMDA) receptors. Additionally, recent clinical studies have shown that memantine, a noncompetitive NMDA receptor antagonist, can significantly improve cognitive functions in some AD patients. However, very little is currently known about the potential role of memantine against Abeta-induced toxicity. In the present study, we have shown that Abeta(1-42)-induced toxicity in rat primary cortical cultured neurons is accompanied by increased extracellular and decreased intracellular glutamate levels. We subsequently demonstrated that Abeta toxicity is induced by increased phosphorylation of tau protein and activation of tau kinases, i.e. glycogen synthase kinase-3beta and extracellular signal-related kinase 1/2. Additionally, Abeta treatment induced cleavage of caspase-3 and decreased phosphorylation of cyclic AMP response element binding protein, which are critical in determining survival of neurons. Memantine treatment significantly protected cultured neurons against Abeta-induced toxicity by attenuating tau-phosphorylation and its associated signaling mechanisms. However, this drug did not alter either conformation or internalization of Abeta(1-42) and it was unable to attenuate Abeta-induced potentiation of extracellular glutamate levels. These results, taken together, provide new insights into the possible neuroprotective action of memantine in AD pathology.

Indomethacin improves locomotor deficit and reduces brain concentrations of neuroinhibitory steroids in rats following portacaval anastomosis.

Hepatic encephalopathy (HE) is a neuropsychiatric complication of both acute and chronic liver failure characterized by progressive neuronal inhibition. Some neurosteroids are potent positive allosteric modulators of the gamma-aminobutyric acid (GABA)-A receptor complex, and 'increased GABAergic tone' has been proposed to explain the neuroinhibition characteristics of HE. Brain levels of the neurosteroids pregnenolone, allopregnanolone and tetrahydrodesoxycorticosterone (THDOC) and the functional status of the GABA-A receptor complex were assessed in rats following portacaval anastomosis (PCA). Effects of indomethacin, an inhibitor of the 3alpha-hydroxysteroid dehydrogenase enzyme involved in neurosteroid synthesis, on PCA rat locomotor activity and brain neurosteroid levels were also assessed. Significant increases of the neurosteroid pregnenolone (2.6-fold), allopregnanolone (1.7-fold) and THDOC (4.7-fold) were observed in brains of PCA rats. Brain levels of these neurosteroids were in the nanomolar range, sufficient to exert positive allosteric modulatory effects at the GABA-A receptor. Indomethacin (0.1-5 mg kg(-1)) ameliorated dose-dependently the locomotor deficit of PCA rats and concomitantly normalized brain levels of allopregnanolone and THDOC. Increased brain levels of neurosteroids with positive allosteric modulatory actions at the neuronal GABA-A receptor offer a cogent explanation for the notion of 'increased GABAergic tone' in HE. Pharmacological approaches using agents that either reduce neurosteroid synthesis or modulate the neurosteroid site on GABA-A receptor could offer new therapeutic tools for the management and treatment of HE.

Neuroactive steroids and fatigue severity in patients with primary biliary cirrhosis and hepatitis C.

Fatigue is one of the most common non-specific symptoms associated with several disease states including liver diseases. Recently, it was reported that levels of progesterone metabolites such as allopregnanolone (3alpha,5alpha-tetrahydroprogesterone; 3alpha,5alpha-THP) and isopregnanolone (3beta,5alpha-THP) were increased in plasma of patients with chronic fatigue syndrome. We hypothesize that THP metabolites might be associated with fatigue commonly observed in chronic liver diseases. We evaluated fatigue scores and plasma levels of five progesterone metabolites in 16 patients with primary biliary cirrhosis (PBC), 12 patients with chronic hepatitis C (CHC) and 11 age-matched controls. The fatigue impact scale (FIS) ratio was significantly increased (P < 0.01) in patients with PBC and CHC compared to controls. Plasma levels of 3alpha,5alpha-THP and pregnanolone (3alpha,5beta-THP) were significantly increased in PBC and CHC patients. The other progesterone metabolites, i.e. 3beta,5alpha-THP, 3beta,5beta-THP and 3alpha,5alpha-tetrahydrodeoxycorticosterone were either undetectable or detected only in some patients. Plasma levels of 3alpha,5alpha-THP and 3alpha,5beta-THP were found to be significantly higher in patients with fatigue (P < 0.05), while those of patients without fatigue were not significantly different from controls. Both 3alpha,5alpha-THP and 3alpha,5beta-THP are positive allosteric modulators of the gamma-aminobutyric acid type A (GABA-A) receptor and readily cross the blood-brain barrier. The present preliminary findings suggest that increased inhibition through GABA-A receptors due to the accumulation of neuroinhibitory steroids may represent an important pathophysiological mechanism of fatigue in chronic liver diseases.

Involvement of cytochromes P450 2D6, 2B6 and 2C19 in the metabolism of (-)-deprenyl and N-methyl,N-propargylphenylethylamine.

The metabolism of (-)-deprenyl (N-methyl,N-propargylamphetamine) and N-methyl,N-propargylphenyl-ethylamine (MPPE), monoamine oxidase inhibitors with neuroprotective properties, was studied using human liver microsomes and cDNA-expressed cytochrome P450 (CYP) enzymes. The metabolic pathways of MPPE parallel those of (-)-deprenyl, but some marked differences were observed, particularly with regard to the contributions of CYP2B6 and CYP2D6.

Phenylethylidenehydrazine, a novel GABA-transaminase inhibitor, reduces epileptiform activity in rat hippocampal slices.

Phenylethylidenehydrazine (PEH), an analog of the monoamine oxidase inhibitor, beta-phenylethylhydrazine (phenelzine), inhibits the gamma-aminobutyric acid (GABA) catabolic enzyme GABA-transaminase and increases brain levels of GABA. GABA is the predominant fast inhibitory transmitter counteracting glutamatergic excitation, and increased neural GABA could influence a wide range of synaptic and circuit properties under both physiologic and pathophysiologic conditions. To examine the scope of these effects, we applied PEH (or vehicle) to rat hippocampal slices and measured basal glutamatergic transmission, synaptic plasticity, and epileptiform activity using extracellular field and whole cell patch clamp recordings. In vitro pre-treatment with PEH (100 microM) increased the GABA content of hippocampal slices by approximately 60% over vehicle-treated controls, but it had no effect on basal field excitatory postsynaptic potentials, tonic GABA currents, paired-pulse facilitation, or long-term potentiation. In contrast, pre-incubation with PEH caused a dose- and time-dependent reduction in epileptiform burst frequency induced by superfusion with Mg2+-free or high-K+ artificial cerebrospinal fluid. Thus, the inhibitory effects of PEH are state-dependent: hyper-excitation during epileptiform bursting was reduced, whereas synaptic transmission and plasticity were unaffected.