Motor and Cognitive Functions in Aging C57BL/6 Mice: Association with Activity of the Monoaminergic Systems in the Cerebellum and Frontal Cortex.

The activity in the open field, short- and long-term memory in the novel object recognition test, and gait features were evaluated in 6- and 12-month-old male C57BL/6 mice. The levels of norepinephrine, dopamine, serotonin, and their metabolites were determined in the cerebellum and frontal cortex. In the observed age range, a decrease in locomotion speed, impairment of gait initiation and stability, and long-term memory deficit were revealed. In the cerebral cortex, reduced levels of dopamine and its metabolites and accelerated metabolism of all neurotransmitters under study were found. In the cerebellum, the content of all studied monoamines was elevated, while dopamine metabolism was decelerated. Analysis of correlations between the neurochemical and behavioral parameters showed that the mechanisms of compensation of brain functions during the early aging may be associated with an increase in activity of the monoaminergic systems in the cerebellum.

Chronic Ethanol Consumption by Rats before Mating Affects Working Memory in the Offspring.

Parameters of non-spatial and spatial memory were evaluated in sexually mature offspring of outbred rats (females and males F0) consuming a 10% ethanol solution for 30 weeks before mating. We found a significant increase in the recognition index in F1 males and its decrease in F1 females in the novel object recognition test. During the first days of the experiment in T-maze, a decrease in spatial memory was revealed in F1 males, which remained at the trend level until the end of testing; no significant deviations were detected in F1 females. Memory impairment in F1 females was accompanied by a decrease in BDNF level in the hippocampus, but not in the prefrontal cortex. Thus, ethanol consumption by F0 rats before mating led to impairment of long-term working memory only in female F1 offspring.

[Behavioral and neuroreceptor effects of the racetam derivative GIZh-290 in mouse experimental attention deficit model]. / Povedencheskie i neiroretseptornye éffekty proizvodnogo ratsetama GIZh-290 s ispol'zovaniem éksperimental'noi modeli defitsita vnimaniia.

Behavioral and neurochemical effects of the new racetam derivative GIZh-290 were studied in a mouse attention deficit model (the ED-Low animals subpopulation selected during preliminary behavioral typing in the "closed enriched cross maze" test). Subchronic administration of GIZh-290 (1 mg/kg, 3 mg/kg and 5 mg/kg, intraperitoneally, for 6 days), increased the initially low level of attention in ED-Low animals; the highest selectivity was observed at a dose of 3 mg/kg. Radioligand analysis showed that at this dose, the drug changed density (Bmax) of D2 and GABAB receptors as markers in the pre-frontal cortex of the ED-Low subpopulation to Bmax values observed in the ED-High subpopulation. In the prefrontal cortex of the ED-Low rodents treated with GIZh-290 in dose of 3 mg/kg, there was a normalization of tissue concentrations of both dopamine itself (DA) and its intra- and extracellular metabolites (DOPA/DA and HVA/DA). The obtained results indicate the effectiveness of the studied drug for pharmacotherapy of attention deficit in experimental modeling and impact on potential molecular targets identified in the study.

Maternal Methyl-Enriched Diet Increases Dopaminergic Tone of the Mesolimbic Brain System in Adult Offspring of WAG/Rij Rats.

The aim of this study is to find out whether maternal methyl-enriched diet affects the content of monoamines and their metabolites in brain structures of adult WAG/Rij offspring. It has been shown for the first time that maternal methyl-enriched diet (choline, betaine, folic acid, vitamin B12, L-methionine, zink) during the perinatal period increases dopaminergic tone of the mesolimbic brain system in adult offspring of WAG/Rij rats, which is accompanied by the suppression of the symptoms of genetic absence epilepsy and comorbid depression. Results suggest that maternal methyl-enriched diet during the perinatal period may be served as a new therapeutic strategy to prevent the development of a hypofunction of the mesolimbic dopaminergic brain system and associated genetic absence epilepsy and comorbid depression in offspring.

Delayed Behavioral and Neurochemical Effects of Anti-Glutamate Antibodies in Aging C57BL/6 Mice.

We analyzed delayed effect of intranasal administration of anti-glutamate antibodies on mnestic function and tissue concentrations of neurotransmitters in the hippocampus and prefrontal cortex in aging C57BL/6 mice. It was found that after 14-day administration of anti-glutamate antibodies, improvement of the passive avoidance conditioning persisted for 7 days after the treatment was discontinued. In 7 days after discontinuation of treatment, increased content of dopamine and its metabolites as well as aspartic acid and taurine was observed in the hippocampus of mice treated with anti-glutamate antibodies. In the prefrontal cortex, administration of anti-glutamate antibodies had no effect on the levels of neurotransmitters, but increased the concentration of glutamate.

Antibodies to Glutamate Facilitate Spatial Memory Formation in the Morris Water Maze in Aging C57BL/6 mice.

Intranasal administration of antibodies to glutamate in a dose of 250 µg/kg for two weeks facilitated spatial learning and memory formation in the Morris water maze in aging C57BL/6 mice. In animals treated with glutamate antibodies, the content of serotonin and dopamine metabolites 3-MT and HVA in the hippocampus decreased, but no changes in the metabolism of neurotransmitter acids were revealed. In the prefrontal cortex, dopamine level decreased and the content of its metabolite DOPAC increased; in parallel, an increase in excitatory and inhibitory amino acids (aspartic acid, glutamate, glycine, taurine, and GABA) was observed.

The Behavioral and Neurochemical Aspects of the Interaction between Antidepressants and Unpredictable Chronic Mild Stress.

The behavioral and neurochemical effects of amitriptyline (10 mg/kg, i.p.) and fluoxetine (20 mg/kg, i.p.) after single and chronic administration in the setting of unpredictable mild stress in outbred ICR (CD-1) mice were studied. After a 28-day exposure to stress, we observed an increase in depressive reaction in a forced swim test in mice, as well as reduced hippocampal levels of serotonin (5-hydroxytryptamine, 5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) and an increased hypothalamic level of noradrenaline (NA). Single and chronic administration of amitriptyline and fluoxetine shortened the immobility period and increased the time corresponding to active swimming in the forced swim test. The antidepressant-like effect of fluoxetine - but not of amitriptyline - after a single injection coincided with an increase in the 5-HT turnover in the hippocampus. Chronic administration of the antidepressants increased the hypothalamic levels of NA. Thus, the antidepressant- like effect of amitriptyline and fluoxetine may result from an enhancement of the stress-dependent adaptive mechanisms depleted by chronic stress.

The Levels of Monoamines and Their Metabolites in the Brain Structures of Rats Subjected to Two- and Three-Month-Long Social Isolation.

The levels of monoamines and their metabolites in the brain structures of adult Wistar rats subjected to post-weaning social isolation for 2 and 3 months were analyzed by HPLC with electrochemical detection. We have previously shown that these rats consistently demonstrate increased aggressiveness and, as a rule, impairment of short-term habituation. Two-monthlong social isolation was accompanied by a reduction in serotonin content and its increased turnover judging from the 5-HIAA/5-HT ratio in the hippocampus; three-month-long isolation was associated with increased levels of serotonin and reduction in its turnover in the amygdala. At this term, the level of dopamine metabolite 3-methoxytyramine tended to increase in the amygdala. In the frontal cortex, a tendency to a decrease in 5-HT level was found. These findings suggest that more prolonged post-weaning social isolation is accompanied by reorganization of neural networks in the brain cortex, which can serve as the pathophysiological basis for psychoemotional disorders.

Selank, Peptide Analogue of Tuftsin, Protects Against Ethanol-Induced Memory Impairment by Regulating of BDNF Content in the Hippocampus and Prefrontal Cortex in Rats.

The effects of a peptide anxiolytic Selank synthesized on the basis of the endogenous peptide tuftsin on memory impairment and content of brain-derived neurotrophic factor (BDNF) in brain structures were analyzed in outbred rats receiving 10% ethanol as the only source of fluid for 30 weeks. In the object recognition test, Selank (0.3 mg/kg a day, 7 days, intraperitoneally) produced a cognitive-stimulating effect in 9 months rats not exposed to ethanol (p<0.05) and prevented the formation of ethanol-induced memory and attention disturbances (p<0.01) developing during alcohol withdrawal. In ex vivo experiments, Selank prevented ethanol-induced increase in BDNF content in the hippocampus and frontal cortex (p<0.05). These results indicate positive effects of the tuftsin analogue on age-related memory disturbances associated with chronic alcohol intoxication and confirm the involvement of the neurotrophin mechanism related to BDNF production into the effect of Selank.

Changes in Monoamine Levels in BALB/c and 57Bl/6N Mice in Response to Acute Stress with Different Controllability.

The severity and specificity of CNS disturbances resulting from negative psychoemotional experience are determined by not only genetically determined stress sensitivity, but also epigenetic factors; among the latter, the context of stress exposure, e.g. stress controllability is considered. We examined the effect of controllability factor on behavioral and neurochemical parameters of acute stress in the elevated plus maze test. The situations of controllable and uncontrollable stress were modeled by allowing or restricting mice in their choice for closed arms during testing in the maze. The anxiety level of inbred BALB/c and C57Bl/6N mice was assessed and the levels and monoamine turnover in the medial prefrontal cortex, hippocampus, amygdala, and hypothalamus were measured. It was found that the decrease in stress controllability suppresses explorative activity in mice; the behavioral and neurochemical differences between the two strains are not constant feature and depend on stress controllability; serotoninergic and dopaminerigic neurotransmission in the hypothalamus can be a signal to discriminate stress controllability in the brain.

Effect of Antibodies to Glutamate on Age-Related Memory Changes in C57Bl/6 Mice.

Chronic intranasal administration of antibodies to glutamate to aging C57Bl/6 mice improved passive avoidance conditioning, had no effect on horizontal and vertical locomotor activity, but slowed locomotion in the open-field test. Administration of antibodies to glutamate increased the content of dopamine and its metabolites in mouse hippocampus, but had no effect on the metabolism of neurotransmitter amino acids. In the frontal cortex, antibodies to glutamate did not affect neurotransmitter metabolism, but increased the level of both excitatory and inhibitory amino acids without changing their ratio.

Dipeptidyl Peptidase 4 Inhibitors Diprotin A and Sitagliptin Administered on Weeks 2-3 of Postnatal Development Modulate Monoamine Metabolism in the Striatum of Adult Rats.

The levels of monoamines and their metabolites in brain structures of adult (3-month-old) rats with emotional and motivational disorders induced by inhibitors of dipeptidyl peptidase 4 (DPP-4; EC 3.4.14.5) diprotin A and sitagliptin on weeks 2-3 of postnatal development (postnatal days 5-18) were studied by HPLC with electrochemical detection. A significant decrease in the level of serotonin metabolite, 5-hydroxyindoleacetic acid, and a pronounced tendency towards reduced serotonin level were detected in the striatum of rats in both study groups. In adult rats treated with diprotin A during the neonatal period, a tendency towards activation of dopamine metabolism was observed (judging from DOPAC/DA ratio). The levels of monoamines and their metabolites in the frontal cortex, hypothalamus, and amygdala remained unchanged. The findings suggest that administration of DPP-4 inhibitors during the neonatal period induces long-term dysfunction of the serotonergic and dopaminergic systems of the brain.

Combined effects of antiorthostatic suspension and ionizing radiation on the behaviour and neurotransmitters changes in different brain structures of rats.

Space flight factors (SFF) significantly affect the operating activity of astronauts during deep space missions. In contrast to an orbital flight, leaving the Earth's magnetic field is fraught with the dangers of exposure to ionizing radiation and more specifically, the high-energy nuclei component of galactic cosmic rays. Microgravity, just another critical non-radiation factor, significantly affects the normal functioning of the CNS. Some morphological structures of the brain, such as the prefrontal cortex and the hippocampus, that are rich in monoaminergic and acetylcholinergic neurones, are the most sensitive to the effects of ionizing radiation and non-radiation spaceflight factors (SFF). In this work we have studied the combined effects of microgravity (in antiorthostatic suspension model, AS) and irradiation (γ-ray and protons in spread-out Bragg peak) on the behaviour, cognitive abilities, and metabolism of monoamines and acetylcholine in the key structures of the rat's brain. Irradiation (as independently as combined with AS) resulted in the decrease of thigmotaxis in rats. Learning problems, caused by the malfunctioning of the working memory but not the spatial memory, were observed in response to AS as well as to the SFF in combination. Analysis of monoamines metabolism showed that the serotoninergic system was the most affected by the SFF. Concentration of acetylcholine in the hippocampus significantly increased in the groups of irradiated rats, and in the groups which were exposed to the SFF in combination, compared to the rats exposed only to AS.

Missing proof of cooperative synthesis of dopamine by non-dopaminergic neurons.

L-DOPA accumulation in the extracellular medium was detected when the transfer of L-DOPA from the neurons containing tyrosine hydroxylase to the neurons containing aromatic L-amino acid decarboxylase was blocked, under conditions of inhibition of the L-DOPA degradation enzyme. Thus, the missing proof confirming the existence of cooperative synthesis of dopamine by neurons non-dopaminergic was obtained.

[NEUROCHEMICAL STUDY OF TROPOXIN EFFECTS ON THE CONTENT OF MONOAMINES AND ITS METABOLITES IN WISTAR RAT BRAIN STRUCTURES].

The influence of perspective anti-migraine drug tropoxin on the content of monoamines and related metabolites in Wistar rat brain structures, including frontal cortex (FC), hypothalamus, nucleus accumbens (NA), striatum, and hippocampus, has been studied using HPLC/ED technique. Tropoxin (10 mg/kg) induced a 30% decrease (p < 0.05) in dopamine (DA) level in FC as well as norepinephrine content in NA, while the concentrations of DA metabolites DOPAC and HVA in the hypothalamus were found to increase. The injection of tropoxin in a dose of 20 mg/kg led to an increase in HVA level in hypothalamus as well as seroto- nin metabolite 5-HIAA content in NA. The obtained data provide evidence that tropoxin predominantly influenced the activity of dopaminergic system while the drug effects on the parameters of serotoninergic link seem to be rather mild.

[STUDYING ANXIOLYTIC AND ANTIDEPRESSANT PROPERTIES OF 2,2,6,6-TETRAMETHYLPIPERIDONE DERIVATIVE.]

Neuropharmacological properties of LK-998 (3,4,5-trimethoxy-N'-(2,2,6,6-tetramethylpiperidin-4-yliden)benzohydrazide), a 2,2,6,6-tetramethylpiperidone de- rivative have been studied. LK-998 exhibited anxiolytic activity in doses of 10 and 20 mg/kg, significantly increasing the duration of animal staying of in open arms of the elevated plus maze as well as the number of arm entries. The efficiency of drug tested in a dose of 10 mg/kg was comparable with that of afobazole in a dose of 5 mg/kg. In marble burying test, it was also found that animals treated with LK-998 at 10 mg/kg buried a close number of balls to that as rodents treated with afobazole at 5 mg/kg. At the same time, LK-998 in doses 10 and 20 mg/kg did not produce any antidepressant action in the learned helplessness test. Thus, LK-998 in a dose of 10 mg/kg has anxiolytic and anticompulsive effects comparable to those of afobazole at a dose of 5 mg/kg. The study of potenti- al side effects of LK- 998 in a dose of 200 mg/kg (i.e., 20 times the therapeutic dose of 10 mg/kg) showed that the drug tested caused neither side effects nor symptoms of neurological deficiency within 24 hours and on longer terms (4, 10 and 14 days after administration).

[Effect of intranasally administered glutamate antibodies on the content of excitatory and inhibitory amino acids in the rat`s hippocampus and hypothalamus at the combined stress exposure].

Objective. We studied the effect of glutamate antibodies by intranasal administration on the development of stress reactions and aspartate, glycine and taurine content in the brain structures of rats with different initial behavioral activity (active and passive). Methods. Stress caused by placing the animals in the living cell with water (21°Ð¡) covered with a grid for 30 min. Glutamate antibodies in a dose of 250 mg/kg in a volume of 10 mkl were administered intranasally to the experimental group of rats immediately after the stress. After 1 h after stress exposure and antibodies administration in all rats was investigated motor activity in the test of the «open field¼. Amino acids aspartate, glycine and taurine in the brain structures (hippocampus and hypothalamus) were determined by HPLC with fluorescence detection. Results. Combined water-immersion stress caused significant changes in the behavioral activity of rats in the «open field¼, but a more pronounced decline in the total index were observed in the behaviorally passive group of rats. The stress was accompanied by a change in the content of neurotransmitter amino acids (glycine and taurine) in the hippocampus. The most significant changes in the levels of glycine (decrease) and taurine (an increase) was observed in the hippocampus behaviorally active rats. Glutamate antibodies at a dose of 250 mg/kg administered intranasally immediately after stress exposure prevents the development of behavioral stress reactions and contributed to an increase in the hippocampus the content of glycine and taurine, related to stress-limiting systems. Conclusions. The glutamate antibodies under stress act as endogenous bioregulators and prevent the development of stress reactions.

Depressive Behavior and Monoamine Contents in Brain Structures of Rats During Chronic Overcrowding.

Effects of chronic overcrowding on the development of depressive-like behavior and changes in monoamine contents in the brain structures involved in the development of depression were studied in rats. It was shown that overcrowding increased grooming duration and did not change the number of crossed squares and postures in the open-field test. In the forced swimming test, overcrowding increased immobility time and deceased the duration of the first episode of active swimming, which attested to depressive-like behavior. Overcrowding reduced the content of dopamine in the striatum, its metabolites (homovanilic and dioxyphenylacetic acids) and dopamine metabolism rate in the hypothalamus, and increased the concentrations of norepinephrine, homovanilic acid, and dioxyphenylacetic acid in the olfactory bulb and homovanilic acid in the prefrontal cortex. No changes were found in the nucleus accumbens. Serotonin content did not change in all analyzed structures. It was hypothesized that the observed changes in the content of monoamines and their metabolites in certain brain structures could underlie the depressive-like behavior induced by overcrowding in rats.

[Concentrations of monoamines in the brain structures and features of behavior in the two-month old WAG/Rij rats].

The first spike-wave discharges (SWDs) in WAG/Rij rats begin to appear at age of 2-3 months and are fully manifested by 5-6 months. Occurrence of SWDs in the EEG is the main indicator of absence epilepsy. Extensive absence epilepsy in 5-6 months-old WAG/Rij rats is accompanied by decreases in dopamine and its metabolites concentrations in the meso-cortico-limbic and nigro-striatal dopaminergic brain systems, resulting in the expression of depression-like behavioral symptoms. In 36 day-old WAG/Rij rats, SWDs are not manifested, deficiency of dopamine is not revealed, and symptoms of depression-like behavior are not expressed. In this study, behavior and monoamines and their metabolites concentrations were investigated in 5 brain structures (prefrontal cortex, nucleus accumbens, hypothalamus, striatum, hippocampus) in 2 month-old WAG/Rij rats in comparison with Wistar rats of the same age. Reduction of the dopamine and its metabolites concentration in 2 month-old WAG/Rij rats was found only in the prefrontal cortex, indicating rapid response of the prefrontal cortex or its high sensitivity. Rapid response of the prefrontal cortex is supposed to be a.fundamental property of this brain structure. Decreases in the dopamine and its metabolites concentration in the prefrontal cortex in 2 month-old WAG/Rij rats were associated with features of behavior which can be regarded as a state of so called pre-pathology (increased anxiety and stress reactivity) preceding the development of depression-like behavior typical for 5-6-months old rats of this strain.

[Age-related changes in behavior, in monoamines and their metabolites content, and in density of D1 and D2 dopamine receptors in the brain structures of WAG/Rij rats with depression-like pathology].

Behavior in the light-dark choice, open field, sucrose consumption/preference and forced swimming tests, monoamines and their metabolites content in 5 brain structures (prefrontal cortex, nucleus accumbens, striatum, hypothalamus, hippocampus), and density of D1- and D2-like dopamine receptors in the prefrontal cortex, nucleus accumbens and ventral tegmental area were studied in WAG/Rij rats at age of 36 days, 3 and 6 months. It has been found that with age, as far as spike-wave discharges aggravate, behavioral symptoms of depression (enhanced immobility in the forced swimming test, reduced sucrose consumption/preference) as well as a hypo-function of the mesolimbic dopaminergic brain system increase in WAG/Rij rats. At age of 36 days, when phenotypic expression of absence epilepsy in WAG/Rij rats is absent, neurochemical alterations in the brain suggesting a hypo-function of the mesolimbic dopaminergic system (deficit of dopamine in the nucleus accumbens), as well as symptoms of depression-like behavior, are not detected. In WAG/Rij rats, as well as in control rats, density of D1-like dopamine receptors in the nucleus accumbens decreased with age. A tendency to a lower density of D1-like dopamine receptors was found in WAG/Rij rats compared with controls at age of 3 months. In contrast with control rats, in WAG/Rij rats, density of D2-like dopamine receptors in the nucleus accumbens increased with age. Higher density of D2-like dopamine receptors was observed in WAG/Rij rats compared with controls only at age of 6 months when a hypo-function of the mesolimbic dopaminergic bran system was extremely pronounced indicating that this increase is a compensatory response to a deficit of dopamine.