Antidepressant and Anxiolytic Effects of L-Methionine in the WAG/Rij Rat Model of Depression Comorbid with Absence Epilepsy.

Depression is a severe and widespread psychiatric disease that often accompanies epilepsy. Antidepressant treatment of depression comorbid with epilepsy is a major concern due to the risk of seizure aggravation. SAMe, a universal methyl donor for DNA methylation and the synthesis of brain monoamines, is known to have high antidepressant activity. This study aimed to find out whether L-methionine (L-MET), a precursor of SAMe, can have antidepressant and/or anxiolytic effects in the WAG/Rij rat model of depression comorbid with absence epilepsy. The results indicate that L-MET reduces the level of anxiety and depression in WAG/Rij rats and suppresses associated epileptic seizures, in contrast to conventional antidepressant imipramine, which aggravates absence seizures. The antidepressant effect of L-MET was comparable with that of the conventional antidepressants imipramine and fluoxetine. However, the antidepressant profile of L-MET was more similar to imipramine than to fluoxetine. Taken together, our findings suggest that L-MET could serve as a promising new antidepressant drug with anxiolytic properties for the treatment of depression comorbid with absence epilepsy. Increases in the level of monoamines and their metabolites-DA, DOPAC, HVA, NA, and MHPG-in several brain structures, is suggested to be a neurochemical mechanism of the beneficial phenotypic effect of L-MET.

Nine-month-long Social Isolation Changes the Levels of Monoamines in the Brain Structures of Rats: A Comparative Study of Neurochemistry and Behavior.

Social isolation (SI) is chronic psycho-emotional stress for humans and other socially living species. There are few comparative studies that have measured monoamine levels in brain structures in male and female rats subjected to SI. Existing data is highly controversial. In our recent study, we investigated behavioral effects of SI prolonged up to 9 months on a rather large sample of 69 male and female Wistar rats. In the present study, we measured the levels of monoamines-norepinephrine (NE), dopamine (DA), 5-hydroxytryptamine (5-HT), and DA and 5-HT metabolites-in the brain structures of 40 rats from the same sample. The single-housed rats of both sexes showed hyperactivity and reduced reactivity to novelty in the Open Field test, and impaired passive avoidance learning. Regardless of their sex, by the time of sacrifice, the single-housed rats weighed less and had lower pain sensitivity and decreased anxiety compared with group-housed animals. SI decreased NE levels in the hippocampus and increased them in the striatum. SI induced functional activation of the DA-ergic system in the frontal cortex and hypothalamus, with increased DA and 3-methoxytyramine levels. SI-related changes were found in the 5-HT-ergic system: 5-HT levels increased in the frontal cortex and striatum, while 5-hydroxyindoleacetic acid only increased in the frontal cortex. We believe that SI prolonged for multiple months could be a valuable model for comparative analysis of the behavioral alterations and the underlying molecular processes in dynamics of adaptation to chronic psychosocial stress in male and female rats in relation to age-dependent changes.

HLDF-6 peptides exhibit neuroprotective effects in the experimental model of preclinical Parkinson's disease.

The mechanisms of the neuroprotective action of the hexapeptides HLDF-6 encoded by the amino acid sequence 41-46 of Human Leukemia Differentiation Factor and its homoserine derivative HLDF-6H were studied in an experimental 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced model of Parkinson's disease (PD). C57Bl/6 mice received two intraperitoneal injections of 18 mg/kg MPTP-HCl, with an interval of 2 hours. MPTP-induced motor dysfunction was assessed using horizontal grid test. Our data show that chronic intranasal administration of peptides (3 weeks, 300 µg/kg/day) restored normal levels of dopamine and improved its turnover rates in the striatum. Furthermore, peptide administration increased serum estradiol levels and led to a significant improvement in motor functions in MPTP-treated mice. Additionally, peptide treatment increased the levels of mRNA encoding neurotrophin BDNF, but normalized the levels of mRNA encoding the inflammatory mediators TGFß1, IL1ß and IFNγ in the brain. Collectively, our behavioral and biochemical studies demonstrate that HLDF-6 peptides have a therapeutic potential for treating PD. We propose that HLDF-6 peptides may exert their neuroprotective mechanism, at least in part, by normalizing estradiol levels and modulating the expression of key factors involved in neurotrophic support and neuroinflammation.

Effects of combined exposure to modeled radiation and gravitation factors of the interplanetary flight: Monkeys' cognitive functions and the content of monoamines and their metabolites; cytogenetic changes in peripheral blood lymphocytes.

In a study on primates (Macaca mulatta), neurobiological and radiobiological effects have been studied of the synchronous combined action of 7-day antiorthostatic hypokinesia and exposure of the monkeys' head first to γ-rays during 24 h and then to accelerated 12C ions. The neurobiological effects were evaluated by the cognitive functions which model the basic elements of operator activity and the concentration of monoamines and their metabolites in peripheral blood. The radiobiological effects were evaluated by the chromosomal aberration and DNA double-strand break (DSB) yield in peripheral blood lymphocytes. The results of the cognitive function research show that the typological features of the animals' higher nervous activity are the prevailing factor that determines changes in these functions. The monkey of the strong balanced type effectively retained its cognitive functions after the exposures, while in the weak unbalanced type animals these functions were impaired. These changes went along with a decrease in the concentration of monoamines and their metabolites and an increase in the DNA DSB and chromosomal aberration yield in lymphocytes.

Semax, synthetic ACTH(4-10) analogue, attenuates behavioural and neurochemical alterations following early-life fluvoxamine exposure in white rats.

Selective serotonin reuptake inhibitors (SSRI) are commonly used to treat depression during pregnancy. SSRIs cross the placenta and may influence the maturation of the foetal brain. Clinical and preclinical findings suggest long-term consequences of SSRI perinatal exposure for the offspring. The mechanisms of SSRI effects on developing brain remain largely unknown and there are no directional approaches for prevention of the consequences of maternal SSRI treatment during pregnancy. The heptapeptide Semax (MEHFPGP) is a synthetic analogue of ACTH(4-10) which exerts marked nootropic and neuroprotective activities. The aim of the present study was to investigate the long-term effects of neonatal exposure to the SSRI fluvoxamine (FA) in white rats. Additionally, the study examined the potential for Semax to prevent the negative consequences of neonatal FA exposure. Rat pups received FA or vehicle injections on postnatal days 1-14, a time period equivalent to 27-40 weeks of human foetal age. After FA treatment, rats were administered with Semax or vehicle on postnatal days 15-28. During the 2nd month of life, the rats underwent behavioural testing, and monoamine levels in brain structures were measured. It was shown that neonatal FA exposure leads to the impaired emotional response to stress and novelty and delayed acquisition of food-motivated maze task in adolescent and young adult rats. Furthermore, FA exposure induced alterations in the monoamine levels in brains of 1- and 2- month-old rats. Semax administration reduced the anxiety-like behaviour, improved learning abilities and normalized the levels of brain biogenic amines impaired by the FA exposure. The results demonstrate that early-life FA exposure in rat pups produces long-term disturbances in their anxiety-related behaviour, learning abilities, and brain monoamines content. Semax exerts a favourable effect on behaviour and biogenic amine system of rats exposed to the antidepressant. Thus, peptide Semax can prevent behavioural deficits caused by altered 5-HT levels during development.

Neurochemical insights into the radiation protection of astronauts: Distinction between low- and moderate-LET radiation components.

Radiation protection of astronauts remains an ongoing challenge in preparation of deep space exploratory missions. Exposure to space radiation consisting of multiple radiation components is associated with a significant risk of experiencing central nervous system (CNS) detriments, potentially influencing the crew operational decisions. Developing of countermeasures protecting CNS from the deleterious exposure requires understanding the mechanistic nature of cognitive impairments induced by different components of space radiation. The current study was designed to identify differences in neurochemical modifications caused by exposure to low- and moderate-LET radiations and to elucidate a distinction between the observed outcomes. We exposed rats to accelerated protons (170 MeV; 0.5 keV/µm) or to carbon ions (12C; 500 MeV/u; 10.5 keV/µm) delivered at the same dose of 1 Gy. Neurochemical alterations were evaluated 1, 30, and 90 days after exposure via indices of the monoamine metabolism measured in five brain structures, including prefrontal cortex, hypothalamus, nucleus accumbens, hippocampus and striatum. We obtained the detailed patterns of neurochemical modifications after exposure to the mentioned radiation modalities. Our data show that the enhancement in the radiation LET from relatively low to moderate values leads to different neurochemical outcomes and that a particular effect depends on the irradiated brain structure. We also hypothesized that exposure to the moderate-LET radiations can induce a hyperactivation of feedback neurochemical mechanisms, which blur metabolic deviations and lead to the delayed impairments in brain functions. Based on our findings we discuss possible contribution of the observed changes to behavioural impairments.

An investigation of the single and combined effects of hypogravity and ionizing radiation on brain monoamine metabolism and rats' behavior.

BACKGROUND: Ionizing radiation and hypogravity can cause central nervous system (CNS) dysfunctions. This is a key limiting factor for deep space missions. Up until now, the mechanisms through which they affect the neural tissue are not completely understood. OBJECTIVES: We studied how the combination of hypogravity (antiorthostatic suspension model, AS) and ionizing radiations (γ-quanta and 1H+ together, R) affects the CNS. METHODS: We applied separately and in combination AS and R to determine the influence of these factors on behavior and metabolism of monoamines in Wistar rat's brain. RESULTS: We found out that R has a slight effect on both the behavior and metabolism of monoamines. However, when applied in combination with AS the former was able to reduce the negative effects of the latter. The combined effect of ionizing radiation and hypogravity led to the recovery of locomotor activity, orientation and exploratory behavior, and long-term context memory impaired under the impact of hypogravity only. These changes came together with an increase in the serotonin and dopamine turnover in all of the brain structures that were studied. CONCLUSIONS: We received the first evidence of interferential interaction between the effects of ionizing radiation and hypogravity factors with regard to a behavior and monoamine turnover in the brain. Further studies with heavy nuclei at relevant doses (<0.5 Gy) are needed.

S100A9 Protein Aggregates Boost Hippocampal Glutamate Modifying Monoaminergic Neurochemistry: A Glutamate Antibody Sensitive Outcome on Alzheimer-like Memory Decline.

Alzheimer's disease (AD) involves dementia conceivably arising from integrated inflammatory processes, amyloidogenesis, and neuronal apoptosis. Glutamate can also cause neuronal death via excitotoxicity, and this is similarly implicated in some neurological diseases. The aim was to examine treatment with in vitro generated proinflammatory protein S100A9 aggregate species alone or with glutamate antibodies (Glu-Abs) on Morris water maze (MWM) spatial learning and memory performance in 12 month old mice. Amino acid and monoamine cerebral neurotransmitter metabolic changes were concurrently monitored. Initially, S100A9 fibrils were morphologically verified by atomic force microscopy and Thioflavin T assay. They were then administered intranasally alone or with Glu-Abs for 14 days followed by a 5 day MWM protocol before hippocampal and prefrontal cortical neurochemical analysis. S100A9 aggregates evoked spatial amnesia which correlated with disrupted glutamate and dopaminergic neurochemistry. Hippocampal glutamate release, elevation of DOPAC and HVA, as well as DOPAC/DA and HVA/DA ratios were subsequently reduced by Glu-Abs which simultaneously prevented the spatial memory deficit. The present outcomes emphasized the pathogenic nature of S100A9 fibrillar aggregates in causing spatial memory amnesia associated with enhanced hippocampal glutamate release and DA-ergic disruption in the aging brain. This finding might be exploited during dementia management through a neuroprotective strategy.

Exposure to (12)C particles alters the normal dynamics of brain monoamine metabolism and behaviour in rats.

Planning of the deep-space exploration missions raises a number of questions on the radiation protection of astronauts. One of the medical concerns is associated with exposure of a crew to highly energetic particles of galactic cosmic rays. Among many other health disorders, irradiation with these particles has a substantial impact on the central nervous system (CNS). Although radiation damage to CNS has been addressed extensively during the last years, the mechanisms underlying observed impairments remain mostly unknown. The present study reveals neurochemical and behavioural alterations induced in rats by 1Gy of 500MeV/u (12)C particles with a relatively moderate linear energy transfer (10.6keV/µm). It is found that exposure to carbon ions leads to significant modification of the normal monoamine metabolism dynamics as well as the locomotor, exploratory, and anxiety-like behaviours during a two-month period. The obtained results indicate an abnormal redistribution of monoamines and their metabolites in different brain regions after exposure. The most pronounced impairments are detected in the prefrontal cortex, nucleus accumbens, and hypothalamus that illustrate the sensitivity of these brain regions to densely ionizing radiations. It is also shown that exposure to (12)C particles enhances the anxiety in animals and accelerates the age-related reduction in their exploratory capability. The observed monoamine metabolism pattern may indicate the presence of certain compensatory mechanisms being induced in response to irradiation and capable of partial restoration of monoaminergic systems' functions. Overall, these findings support a possibility of CNS damage by space-born particles of a relatively moderate linear energy transfer.

The misfolded pro-inflammatory protein S100A9 disrupts memory via neurochemical remodelling instigating an Alzheimer's disease-like cognitive deficit.

Memory deficits may develop from a variety of neuropathologies including Alzheimer's disease dementia. During neurodegenerative conditions there are contributory factors such as neuroinflammation and amyloidogenesis involved in memory impairment. In the present study, dual properties of S100A9 protein as a pro-inflammatory and amyloidogenic agent were explored in the passive avoidance memory task along with neurochemical assays in the prefrontal cortex and hippocampus of aged mice. S100A9 oligomers and fibrils were generated in vitro and verified by AFM, Thioflavin T and A11 antibody binding. Native S100A9 as well as S100A9 oligomers and fibrils or their combination were administered intranasally over 14 days followed by behavioral and neurochemical analysis. Both oligomers and fibrils evoked amnestic activity which correlated with disrupted prefrontal cortical and hippocampal dopaminergic neurochemistry. The oligomer-fibril combination produced similar but weaker neurochemistry to the fibrils administered alone but without passive avoidance amnesia. Native S100A9 did not modify memory task performance even though it generated a general and consistent decrease in monoamine levels (DA, 5-HT and NA) and increased metabolic marker ratios of DA and 5-HT turnover (DOPAC/DA, HVA/DA and 5-HIAA) in the prefrontal cortex. These results provide insight into a novel pathogenetic mechanism underlying amnesia in a fear-aggravated memory task based on amyloidogenesis of a pro-inflammatory factor leading to disrupted brain neurochemistry in the aged brain. The data further suggests that amyloid species of S100A9 create deleterious effects principally on the dopaminergic system and this novel finding might be potentially exploited during dementia management through a neuroprotective strategy.

Noradrenergic and serotonergic neurochemistry arising from intranasal inoculation with α-synuclein aggregates which incite parkinsonian-like symptoms.

Alpha-synuclein (α-syn) toxic aggregates delivered by the nasal vector have been shown to modify the neurochemistry of dopamine (DA) which is associated with parkinsonian-like motor symptoms. The aim was therefore to study the intranasal effects of α-syn oligomers, fibrils or their combination on the motor behavior of aged mice in relation to possible noradrenergic and serotonergic correlates. In vitro generated α-syn oligomers and fibrils were verified using atomic force microscopy and the thioflavin T binding assay. Levels of noradrenaline (NA), serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) were detected using HPLC with electrochemical detection in the substantia nigra (SN) and striatum. The oligomers or fibrils administered alone or in a 50:50 combination (total dose of 0.48 mg/kg) were given intranasally for 14 days and "open-field" behaviour was tested on days 0, 15 and 28 of the protocol, at which time brain structures were sampled. Behavioral deficits at the end of the 14-day dosing regime and on day 28 (i.e. 14 days after treatment completion) induced hypokinesia and immobility whilst the aggregate combination additionally produced rigidity. The α-Syn oligomer/fibril mixture also instigated PD-like motor symptoms which correlated heterochronically with elevated NA levels in the striatum but then later in the SN while intranasal fibrils alone augmented 5-HT and 5-HIAA nigral concentrations throughout the protocol. In contrast, α-syn oligomers displayed a delayed serotonin upsurge in the SN. Neurodegenerative and/or actions on neurotransmitter transporters (such as NET, SERT and VMAT2) are discussed as being implicated in these α-syn amyloid induced neurochemical and motoric disturbances.

Intranasal administration of alpha-synuclein aggregates: a Parkinson's disease model with behavioral and neurochemical correlates.

Parkinson's disease (PD) is a neurodegenerative disorder in which both alpha-synuclein (α-syn) and dopamine (DA) have a critical role. Our previous studies instigated a novel PD model based on nasal inoculation with α-syn aggregates which expressed parkinsonian-like behavioral and immunological features. The current study in mice substantiated the robustness of the amyloid nasal vector model by examining behavioral consequences with respect to DA-ergic neurochemical corollaries. In vitro generated α-syn oligomers and fibrils were characterized using atomic force microscopy and the thioflavin T binding assay. These toxic oligomers or fibrils administered alone (0.48 mg/kg) or their 50:50 combination (total dose of 0.48 mg/kg) were given intranasally for 14 days and "open-field" behavior was tested on days 0, 15 and 28 of the protocol. Behavioral deficits at the end of the 14-day dosing regime and on day 28 (i.e., 14 days after treatment completion) induced rigidity, hypokinesia and immobility. This was accompanied by elevated nigral but not striatal DA, DOPAC and HVA concentrations in response to dual administration of α-syn oligomers plus fibrils but not the oligomers by themselves. α-Syn fibrils intensified not only the hypokinesia and immobility 14 days post treatment, but also reduced vertical rearing and enhanced DA levels in the substantia nigra. Only nigral DA turnover (DOPAC/DA but not HVA/DA ratio) was augmented in response to fibril treatment but there were no changes in the striatum. Compilation of these novel behavioral and neurochemical findings substantiate the validity of the α-syn nasal vector model for investigating parkinsonian-like symptoms.

Strain differences in profiles of dopaminergic neurotransmission in the prefrontal cortex of the BALB/C vs. C57Bl/6 mice: consequences of stress and afobazole.

We found that in mice the basal activity of monoamine oxidase B (MAO-B) in the medial prefrontal cortex (mPFC) is lower in BALB/C than in C57Bl/6J mice, whereas activity of MAO-A is similar between strains. BALB/C mice, in comparison to C57Bl/6N mice, have higher basal content of dopamine in the mPFC, in both microdialysates and tissue content. Novelty stress (open field test) elicits a further increase in the microdialysate levels of dopamine in BALB/C, but not in C57Bl/6N mice; a subsequent accumulation of extracellular 3,4-dioxyphenylacetic acid (DOPAC) reaffirms the difference in catabolic capacity of monoaminergic systems between the strains. We demonstrated that in stress-susceptible BALB/C mice the novel anxiolytic afobazole, 5mg/kg, selectively mitigates trait anxiety; however it does not change the behavioral response in stress-resilient C57Bl/6N mice. Afobazole inhibits MAO-A in in vitro; it also lowers the microdialysate DOPAC levels in both strains (which testifies to its MAO-A inhibiting activity in vivo) and slightly suppresses dopamine release when elevated. Therefore, it is likely that the drug may mediate its anxiolytic activity via modulation of volume dopaminergic transmission at level of the mPFC.

Disrupted serotonergic and sympathoadrenal systems in patients with chronic heart failure may serve as new therapeutic targets and novel biomarkers to assess severity, progression and response to treatment.

BACKGROUND: It is well established that the serotonergic system (SS) plays important roles in the pathogenesis of cardiovascular diseases. However, the impact of serotonin and its inter-relation with the sympathoadrenal system (SAS) in chronic heart failure (CHF) is poorly understood. METHODS: Utilizing high-performance liquid chromatography with electrochemical detection, we determined blood plasma levels of serotonin (5-hydroxy-triptamine, [5-HT](p)), 5- hydroxy-indole-acetic acid ([5-HIAA](p)), epinephrine ([E](p)), norepinephrine ([NE](p)), 3,4-dihydroxy-L-phenyl-alanine ([DOPA](p)), dopamine ([DA](p)) and the platelet concentration of serotonin ([5-HT](pt)) in CHF patients with different morphofunctional alterations of myocardium. The morphofunctional alterations included diastolic dysfunction (DD), diastolic dysfunction with left ventricular hypertrophy (DD&LVH), and diastolic and systolic dysfunction (D&SD). RESULTS: All CHF groups showed significant rises of [5-HT](p) and [5-HT](pt). DD&LVH and D&SD individuals also had increased [5-HIAA](p). Levels of SAS blood biomarkers were also significantly changed. The correlation between SS and SAS was increased in CHF and corresponded with disease severity. CONCLUSIONS: These results clearly demonstrate that in CHF patients significant changes in SS and SAS occur, which are thought to relate to the morphofunctional alterations of myocardium. The observed changes in the levels of these biomarkers may serve as potential surrogates to monitor severity of disease, to evaluate response to drug treatment, and as a rational basis for new therapeutic approaches.

Maternal para-chlorophenylalanine exposure modifies central monoamines and behaviors in the adult offspring.

We reported a perspective animal model of neurodevelopmental disorders using rats prenatally exposed to an inhibitor of serotonin (5HT) synthesis, para-chlorophenylalanine (PCPA). Earlier, we demonstrated that prenatal exposure to PCPA caused fetal 5HT depletion and changes both in open field activity and in depression-related behavior, as well as impairments in spatial learning in the adult offspring (Vataeva et al., 2007). The present study revealed that prenatal PCPA treatment resulted in the offspring's significantly reduced anxiety-related behavior in the elevated plus-maze and reduced neophobia to intake fluids in a novel environment. These effects are accompanied by hedonic changes in the form of an appropriate increase in saccharin preference. We confirmed our earlier finding that prenatal PCPA exposure affected the open field locomotor activity. In the present study we have shown that the selective 5HT reuptake inhibitor (SSRI) paroxetine decreases locomotor activity in the prenatally PCPA-treated offspring. It was also found that in the PCPA-treated fetal brain, 5HT depletion was associated with a significant decrease in the level of dopamine (DA) metabolite dihydroxyphenylacetic acid (DOPAC) and with a reduction of DOPAC/DA and homovanillic acid (HVA)/DA ratios. An assay of adult offspring brain revealed that the prenatal PCPA produced different effects on monoamines in the studied brain structures. The relationships between behavioral abnormalities and alterations in brain monoamine levels consequent on the prenatal PCPA treatment are discussed.

Behavioral alteration in the adult rats prenatally exposed to para-chlorophenylalanine.

In the present work, effects of maternal administration of para-chlorophenylalanine (PCPA), a serotonin synthesis inhibitor, on behavior of adult offspring were studied. Pregnant rats were injected intraperitoneally with PCPA (200/100/100/50 mg/kg) either on the gestational days (GD) 8-11 or 14-17, or with vehicle at the same days. Behavioral parameters, in an open field, the Porsolt forced swim test and the Morris water maze test were evaluated at the age of 3-3.5 months in the male and female offspring. The prenatal PCPA increased activity in an open field in the offspring treated on either GD 8-11 or 14-17. The highest levels of the activity were revealed in the male and female offspring treated on GD 14-17. Besides, the PCPA treatment on GD 8-11 or 14-17 facilitated the intersession habituation of activity to repeated exposures to an open field in the male offspring. Both male and female offspring treated on GD 14-17 showed an increased immobility in the Porsolt forced swim test and a significant learning impairment in the Morris water maze. Thus, it has been shown that administration of PCPA to pregnant rats might cause significant changes in the adult offspring behavior. These results provide further evidence that unfavorable influence may have more adverse effects on the behavioral development of rats when exposed during the final trimester of pregnancy than during the second trimester.

Semax, an ACTH(4-10) analogue with nootropic properties, activates dopaminergic and serotoninergic brain systems in rodents.

Corticotrophin (ACTH) and its analogues, particularly Semax (Met-Glu-His-Phe-Pro-Gly-Pro), demonstrate nootropic activity. Close functional and anatomical links have been established between melanocortinergic and monoaminergic brain systems. The aim of present work was to investigate the effects of Semax on neurochemical parameters of dopaminergic- and serotonergic systems in rodents. The tissue content of 5-hydroxyindoleacetic acid (5-HIAA) in the striatum was significantly increased (+25%) 2 h after Semax administration. The extracellular striatal level of 5-HIAA gradually increased up to 180% within 1-4 h after Semax (0.15 mg/kg, ip) administration. This peptide alone failed to alter the tissue and extracellular concentrations of dopamine and its metabolites. Semax injected 20 min prior D: -amphetamine dramatically enhanced the effects of the latter on the extracellular level of dopamine and on the locomotor activity of animals. Our results reveal the positive modulatory effect of Semax on the striatal serotonergic system and the ability of Semax to enhance both the striatal release of dopamine and locomotor behavior elicited by D-amphetamine.