[Possible role of serotonin 5-HT2 receptors in mechanism of afobazole anxiolytic action: neurochemical study of inter-line differences in mice].

Effects of separate and combined introduction of afobazole and SB-200646A (highly selective 5-HT2B/2C receptor antagonist) on the content of monoamines and their metabolites in brain structures of mice of C57/Bl/6 and BALB/C lines have been studied using neurochemical methods and high-performance liquid chromatography (HPLC). Afobazole (5 mg/kg, i.p.) significantly increased dopamine (DA) level in hypothalamus and amygdala of C57/Bl/6 mice, while no changes of DA content were observed in BALB/C mice. At the same time, the concentrations of DA metabolites dioxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) in the same structures as well as in striatum were decreased compared to control. Afobazole also led to a decrease in the content of 5-hydroxyindoleacetic acid (5-HIAA) and 5-HIAA/5-HT index in frontal cortex and amygdala of C57/Bl/6 mice; analogous decrease in the latter parameter was observed in striatum of BALB/C mice. The introduction of SB-200646A (10 mg/kg, i.p.) almost did not influence the neurochemical indices of the content and metabolism of monoamines, except for an increase in the HVA content in amygdala and the DOPAC and 5-HIAA concentrations in striatum of C57/Bl/6 mice. The joint introduction of afobazole and SB-200646A led to an increase in the content of norepinephrine (NE) in striatum of BALB/C mice and in hippocamp of mice of both lines. The data obtained may be indicative of the involvement of NE- and DA-ergic neurotransmitter systems in the mechanisms of afobazole action. Enhanced anxiolytic effect of the joint introduction of afobazole and SB-200646A can be interpreted as a positive modulation of the anxiolytic drug action related to the blocking of 5-HT2-type serortonin receptors. The results also reveal inter-line differences of neurochemical responses induced by combination of afobazole and selective antagonist of serotonin.

Experimental modeling of preclinical and clinical stages of Parkinson's disease.

Degeneration of dopaminergic (DAergic) neurons of the nigrostriatal system is the key stage in the pathogenesis of Parkinson's disease. The first symptoms of this disease are observed after degeneration of 70-80% neurons, which occurs over 20-30 years. The clinical stage of Parkinson's disease begins after this period. Late diagnostics of Parkinson's disease contributes to low efficiency of therapy for this disorder. Detailed study of the pathogenesis and development of preclinical diagnostic methods for Parkinson's disease are the urgent problems. This work was designed to develop a new experimental model of the preclinical and clinical stages of the disease. Experimental modeling was performed on C57Bl/6 mice using 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). This agent is converted into the MPP(+)-neurotoxin in brain DAergic neurons. We showed that MPTP in a dose of 4 mg/kg has no effect on the nigrostriatal DAergic system. MPTP in a dose of 8-16 mg/kg produced the toxic effect only on DAergic axons, which simulates the preclinical stage of Parkinson's disease. MPTP in a dose of 20-40 mg/kg had the toxic effect on neuronal axons and bodies, which simulates the clinical stage of Parkinson's disease. The data suggest that progressive degeneration of DAergic neurons is accompanied by activation of compensatory mechanisms for functional deficiency of these cells.

[Levetiracetam modifies the pattern of audiogenic locomotive response in Wistar and Krushinsky-Molodkina strain rats].

The novel antiepileptic drug levetiracetam (keppra, 80 mg/kg, i.p.) produces a pronounced anticonvulsant effect on all parameters of the audiogenic locomotion response in Wistar rats, leading to the prevention of acoustic seizures approximately in 50% animals. Keppra injection also led to a decrease in the intensity of single audiogenic convulsive episode, a twofold prolongation of the latency of motor reaction, and a change in the pattern of seizure reaction toward increasing number of rats with "one-wave" response. In contrast, a lack of sound resistant animals and the change from one- to two-wave audiogenic response were observed in Krushinsky-Molodkina strain rats.

[Modeling of preclinical and early clinical stages of Parkinson's disease].

The first symptoms of Parkinson's disease manifest 20-30 years after the disease onset when the most dopaminergic neurons degenerated. Therefore, it is necessary to work out preclinical diagnostics and preventive treatment of this disease. Modeling of preclinical and early stages of Parkinson's disease was conducted in mice using 1-methyl-4-phenyl-1,2,3,6-tetrahydropiridine (MPTP). The changes in motor behavior were not observed in mice by 14 day after MPTP injections in dose 12 mg/kg two times with interval of two hours. In the striatum, the region of dopaminergic axon projection, the content of dopamine and number of dopaminergic axons decreased by 57% and 59%, respectively, i.e. there were no changes in dopamine in single axons. In the substantia nigra, the region of dopamine neuron localization, the content of dopamine did not change though the total number of neurons decreased by 28%. However the dopamine content in remained neurons was higher by 77% compared to the control that indirectly indicated the compensatory enhancement of dopamine synthesis. After the MPTP injections in dose 4x12 mg/kg, there were changes in motor behavior of mice in the most sensitive tests. In the striatum, the dopamine content and number of dopaminergic axons decreased by 75% and 68%, respectively. In the substantia nigra, there were no changes in dopamine content but the number of dopaminergic neurons decreased by 43%. The intraneuronal dopamine content increased by more than 70%. In conclusion, we constructed the models of preclinical stage (two-time MPTP injections) and transition phase from presymptomatic to symptomatic stage (four times of MPTP injections) of Parkinson's disease.

[Experimental modeling of functional deficiency of the nigrostriatal dopaminergic system in mice].

The dopaminergic nigrostriatal system is a key component of regulation of the motor behaviour. Cell bodies of dopaminergic DA-ergic neurons are located in the compact zone of the substantia nigra, and their axons are projected along the nigrostriatal tract to the striatum. This study was aimed to develop an experimental model of the functional insufficiency of the DA-ergic neurons of the nigrostriatal system without any manifestation of movement disorders, i.e., a model of presymptomatic stage of parkinsonism. This model has been developed with a single subcutaneous injection of a low dose of MPTP (12 mg/kg) which is converted in the brain into the MPP+, a neurotoxin of DA-ergic neurons. It has been shown that the MPTP injection on the 14th day is followed by: (a) absence of any sign of movement disorders; (b) no change in the DA content and the number of DA-ergic neurons in the substantia nigra; (c) substantial loss of DA in the striatum as a result of the degeneration of about 50% of DA-ergic axons. The absence of movement disorders under the substantial DA depletion and degradation of DA-ergic axons in the striatum is supposed to be a consequence of the turning on of the compensatory processes in the brain. Thus, we have developed the experimental model of presymptomatic stage of parkinsonism which is characterized by the degeneration of DA-ergic axons in the striatum without degradation of the neuron cell bodes in the substantia nigra.

[Development of central and peripheral serotonin-producing systems in rats in ontogenesis].

The work deals with study of development of central and peripheral serotonin-producing systems in rat ontogenesis before and after formation of the blood-brain barrier. By the method of highly efficient liquid chromatography it has been shown that the serotonin level in peripheral blood before formation of the blood-brain barrier (in fetuses and neonatal rats) is sufficiently high for realization of physiological effect on target cells and organs. At the period of formation of the blood-brain barrier the serotonin level in brain sharply rises, whereas the serotonin concentration and amount in plasma and duodenum increase insignificantly. Completion of formation of the blood-brain barrier is accompanied by a significant increase of the serotonin content in duodenum, probably for maintenance of the high serotonin level in blood. To evaluate secretory activity, the mean rate of daily increment of the serotonin in the studied tissues was calculated. In brain, this parameter was maximal at the period of formation of the blood-brain barrier and then sharply fell, whereas in duodenum it rose markedly after completion of the barrier formation. In plasma this parameter decreased statistically significantly at the period of formation of the blood-brain barrier - from the 4th to the 16th postnatal days. This allows thinking that brain before formation of the blood-brain barrier is a most important source of serotonin in peripheral blood.

[Effects of heptapeptide selank on the content of monoamines and their metabolites in the brain of BALB/C and C57Bl/6 mice: a comparative study].

The effect of heptapeptide selank on the content of neurotransmitter monoamines and its metabolites in the brain structures of BALB/C and C57Bl/6 line mice under conditions of the open-field test were studied. Significant interstrain differences in the content of norepinephrine (NE), dopamine (DA), serotonin (5-HT) as well as in the levels of their metabolites in hippocampus, hypothalamus, striatum and frontal cortex of C57Bl/6 and BALB/C mice were demonstrated. In particular, the content of 5-HT and its metabolite 5-oxyindolacetic acid (5-HIAA) in hippocampus of BALB/C mice (with passive stress response) was higher than in the same structure of C57Bl/6 (stress-susceptible) animals. The injection of selank (0.3 mg/kg) led to an increase in the NE level in the hypothalamus of both mice strains. At the same time, selank produced opposite effects on the content of DA metabolites: the concentrations of dioxyphenylacetic (DOPAC) and homovanillic (HVA) acids were found to increase in frontal cortex and hippocampus of C57Bl/6 mice, while the same parameters in BALB/C mice were demonstrated to decrease. Selank induced a decrease in 5-HT and 5-HIAA levels in the hippocampus of BALB/C mice, but did not affect these parameters in C57Bl/6 animals. The obtained results are indicative of selectivity of the anxiolytic effects of selank.

[The investigation of cataleptic muscle tonus changes in rats after audiogenic seizures].

The duration and severity of cataleptic freezing after audiogenic seizures were investigated in rats of several genotypes with different predisposition to audiogenic epilepsy. These genotypes were the Krushinsky-Molodkina strain (KM--the audiogenic seizure prone strain), the Wistar and two new substrains selected from hybrids KM x Wistar for high ("4") and low ("0") audiogenic seizure susceptibility. The drug injections, which modulated the audiogenic fit severity, induced the changes in catalepsy too. It was found, that in intact animals cataleptic freezing developed after audiogenic seizures only and was more intense after severe seizures, the correlation coefficient being statistically significant. Levetiracetam (anticonvulsant drug) injections resulted in significant decrease of audiogenic fit severity and cataleptic state in Wistar and KM rats. Caffeine injections resulted in audiogenic seizures accompanied by cataleptic freezing in rats of the substrain "0", selected for audiogenic non-pronness.

[Neuronal and neurochemical mechanisms underlying the effect of a novel antiepileptic drug levetiracetam].

Published data on the mechanisms involved in the action of levetiracetam (LVT, 2S-(oxo-1-pyrrolidinyl)butanoic acid amide), a widely used agent for the adjunctive therapy of partial epilepsy of different genesis, have been analyzed. A unique profile of the anticonvulsant action of LVT was already revealed at the screening stage: this agent was not effective in the traditional tests, but it demonstrated a pronounced protective effect in kindling models and in the experiments on mice sensitive to the audiogenic convulsions. Now it is commonly accepted that the LVT mode of action is different from that of the other known antiepileptic drugs. LVT was shown to have specific binding sites in the brain. It is believed that the synaptic vesicle protein SV2A is the binding site for LVT, and the main mechanism of its action involves the modulation of this protein functions, which probably accounts for the unique profile of the antiepileptic activity of LVT. The results of investigations of the neurochemical mechanisms of LVT action suggest that proteins involved in the vesicular exocytosis, in particular SV2, can be promising targets in the search for new effective agents for the treatment of CNS diseases.

[Anticonvulsant effects of levetiracetam on audiogenic epileptiform siezures in Krushinsky-Molodkina rats].

The new antiepileptic drug levetiracetam (LVT) at doses of 40 and 80 mg/kg exhibits a pronounced anticonvulsant effect, influencing all the parameters of audiogenic epileptiform seizures (AES) in Krushinsky-Molodkina (KM) rats. The latent period of the motor reaction was increased 3-15 times compared to control, and the intensity of single convulsive episodes was significantly decreased. Changes were also detected in the profile of the first stage of motor activity, and the "two-wave" reaction was observed in 50-80% of animals. The mechanism of LVT anticonvulsant action in KM rats is probably associated with an increase in the inhibitory and a decrease in the excitatory processes in the CNS.

Dopamine synthesis by non-dopaminergic neurons in the arcuate nucleus of rat fetuses.

The aim of the present work was to verify the hypothesis that non-dopaminergic neurons expressing individual complementary dopamine synthesis enzymes can perform the co-located synthesis of dopamine. According to this hypothesis, neurons expressing tyrosine hydroxylase use L-tyrosine for the synthesis of L-dihydroxyphenylalanine (L-DOPA), which then enters neurons expressing aromatic amino acid decarboxylase, which converts L-DOPA to dopamine. Experiments were performed using the mediobasal hypothalamus of rat fetuses, which mostly contains single-enzyme neurons (>99%) and occasional double-enzyme neurons (<1%). Controls were obtained from the fetal substantia nigra, which is enriched with dopaminergic neurons. High-performance liquid chromatography was used to measure levels of dopamine and L-DOPA in cell extracts and the incubation medium after incubation in the presence and absence of exogenous L-tyrosine. Addition of L-tyrosine to the medium led to increases in the level of synthesis and release of L-DOPA in the mediobasal hypothalamus and substantia nigra. In addition, L-tyrosine increased dopamine synthesis in the substantia nigra and decreased dopamine synthesis in the mediobasal hypothalamus. This regional difference in levels of dopamine synthesis is probably due to inhibition of the uptake of L-DOPA from the intercellular medium by neurons in the mediobasal hypothalamus containing aromatic amino acid decarboxylase, due to the competitive binding of the L-DOPA transporter by L-tyrosine. Thus, these results provide the first evidence for the co-located synthesis of dopamine by non-dopaminergic neurons expressing single complementary enzymes involved in the synthesis of this neurotransmitter.

[Dopamine synthesis by non-dopaminergic neurons of the rat fetus arquate nucleus]. / Sintez dofamina nedofaminergicheskimi neironami arkuatnogo iadra plodov krys.

Our hypothesis was tested in respect to dopamine synthesis by non-dopaminergic neurons expressing individual complementary enzymes of the DA synthetic pathway. According to the hypothesis, L-dihydroxyphenylalanine (L-DOPA) synthesised in tyrosine hydroxylase(TH)-expressing neurons for conversion to dopamine. The mediobasal hypothalamus of rats on the 21st embryonic day was used as an experimental model. The fetal substantia nigra containing dopaminergic neurons served as control. Dopamine and L-DOPA were measured by high performance liquid chromatography in cell extracts and incubation medium in presence or absence of L-tyrosine. L-tyrosine administration increased L-DOPA synthesis in the mediobasal hypothalamus and substantia nigra. Moreover, L-tyrosine provoked an increase of dopamine synthesis in substantia nigra and a decrease in the mediobasal hypothalamus. This is, probably, due to an L-tyrosine-induced competitive inhibition of the L-DOPA transport to monoenzymatic AADC neurons after its release from the monoenzymatic TH neurons. This study provides a convincing evidence of dopamine synthesis by non-dopaminergic neurons expressing TH or AADC, in cooperation.

[The interstrain differences in the effects of D-amphetamine and raclopride on dorsal striatum dopaminergic system in KM and Wistar rats (microdialysis study)]. / Mezhlineinye razlichiia v éffekta amfetamina i rakloprida na aktivnost' dofaminergicheskoi sistemy v dorzal'nom striatume u krys linii KM i Vistar (mikrodializnoe issledovanie).

The levels of dopamine (DA) was determined by intracerebral microdialysis in vivo in KM rats selected for high audiogenic epilepsy, and in Wistar rats selected for nonsusceptibility to loud sound. The basal level of dopamine was 25% higher in the KM rats (P < 0.05). A single amphetamine injection (1 mg/kg body weight, intraperitoneously) caused a significant increase in the DA basal level up to 250-260% in animals of both genotypes. However, in Wistar rats, the level of DA reached maximum as soon as 20 min after amphetamine administration, whereas in KM rats, this happened only after 120 min. After a single injection of the antagonist of D2 and D3 dopamine receptors raclopride (1.2 mg/kg of body weight, intraperitoneously), an increase in the level of DA was similar in amplitude in rats of both genotypes (up to about 210%); however, this occurred 20-30 and 100 min after raclopride administration to Wistar and KM rats, respectively. This evidence suggests that the genetic defect of KM rats, namely, the high level of audiogenic epilepsy, is caused by abnormalities of the neuromediator brain systems and presumably accompanied by the regulatory gene dysfunction.

Dizocilpine blocks the effects of delta sleep-inducing peptide-induced suppression of c-fos gene expression in the paraventricular nucleus of the hypothalamus in rats.

The characteristics of the actions of the non-competitive blocker of NMDA receptors dizocilpine on the expression of the early c-fos gene in the paraventricular nuclei of the hypothalamus were studied in rats with different predicted susceptibilities to emotional stress in conditions of treatment with delta sleep-inducing peptide. The results showed that prior treatment with dizocilpine blocked reductions in c-fos expression induced by delta sleep peptide.

[Semax potentiates effects of D-amphetamine on the level of extracellular dopamine in the Sprague-Dawley rat striatum and on the locomotor activity of C57BL/6 mice]. / Semaks usilivaet éffekty D-amfetamina na uroven' vnekletochnogo dofamina v striatume krys Spreg-Douli i na lokomotornuiu aktivnost' myshei C57BL/6.

The synthetic peptide semax (a fragment of ACTH 4-7 Pro-Gly-Pro) enhances the release of extracell dopamine (DA) induced by D-amphetamine (5 mg/kg) in the striatum of Spraig-Dowley (SD) rats and increases the locomotor activity stimulated by D-amphetamine (2 mg/kg) in C57/BL6 mice. The basal content of DA, 3,4-dihydroxyphenylacetic acid (DHPAA), and homovanillic acid (HVA) in dialysate of SD rats was 0.5-1.0, 996 +/- 25, and 761 +/- 37 pmole/ml, respectively (n = 7). D-amphetamine (5 mg/kg) induced a sharp increases in the DA level (up to 20 pmole/ml) 20-40 min after treatment and reduced the extracell DHPAA content to 30% of the basal level for a prolonged time (over the entire experimental period). Preliminary (20 min before D-amphetamine) administration of semax resulted in a greater peak of DA concentration (p < 0.05) and a more pronounced drop in DHPAA level (p < 0.01) as compared to the effects produced by the psychostimulant alone. In behavioral tests on C57/BL6 mice, D-amphetamine (2 mg/kg) increased the locomotor activity to a level of 182% (p < 0.01). Simultaneous introduction of semax (0.6 mg/kg) and D-amphetamine (2 mg/kg) led to a more pronounced increase in the locomotor activity of mice (261%, p < 0.01). It is suggested that the peptide modulates dopaminergic systems involved in the formation of the psychostimulant effect.

[Allosteric modulators of AMPA type glutamate receptors a novel gubclass of physiologically active substances]. / Allostericheskie moduliatory glutamatnykh retseptorov AMPA-podtipa - novyi klass fiziologicheski aktivnykh veshchestv.

Properties of AMPA type glutamate receptors widely presented within mammalian central nervous system are reviewed. AMPA receptors belong to ionotropic subclass of glutamate receptors and participate in fast excitatory glutamatergic transmission in the brain. Molecular structure of AMPA receptors consists of several subunits (GluRA1-GluRA4), which display various sensitivity to receptor ligands. These receptors are named according to their selective agonist alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA). AMPA receptor modulators represented by several chemical groups: pyrrolidinones (aniracetam), benzothiodiazinedioxides, benzylpiperidines and biarylpropylsulphonamides. These compounds facilitate AMPA receptor-mediated glutamatergic neurotransmission. AMPA receptor modulators enhance cognitive functions (learning and memory), reveal anxiolytic and antidepressant action, suppress the effects of psychostimulant agents, potentiate the effects of antipsychotic drugs, display neuroprotective properties. Positive modulation of AMPA receptor-associated ionic channels was shown to underline the mode of action of these substances that results in enhancement of long-term potentiation (LTP) and increasing neurotrophic factors expression. Preliminary clinical results have shown positive therapeutic effect of these substances in patients with cognitive impairment.

Role of nitric oxide and lipid peroxidation in pathophysiological mechanisms of audiogenic seizures in GEP Rats and DBA/2 mice.

We evaluated the role of nitric oxide and lipid peroxidation in the pathophysiological mechanisms of seizures in genetically epilepsy prone (GEP) rats and DBA/2 mice with genetically determined audiogenic epilepsy. In rats and mice acoustic stimulation led to locomotor activation followed by clonic-tonic seizures. The contents of nitric oxide and lipid peroxidation products at the peak of seizures markedly surpassed the control level.

[Antipsychotic agents: from phenothiazines to atypical neuroleptics of the second generation]. / Antipsikhoticheskie sredstva: ot fenotiazinov k atipichnym neiroleptikam novogo pokoleniia.

The paper addresses evolution of the problem of creation, characterization of the pharmacological properties, and elucidation of the mechanisms of action of antipsychotic drugs (neuroleptics)--one of the most important classes of modern psychotropic drugs. The appearance of these drugs marked the onset of a new era in psychiatry, the era of psychopharmacology. Special attention is devoted to the investigations in this direction at the Institute of Pharmacology, which were headed by V. V. Zakusov.

[Dizocilpine inhibits suppression of c-fos gene by delta-sleep peptide in the rat hypothalamic paraventricular nucleus]. / Dizotsilpin blokiruet éffekty podavlenia peptidom del'ta-sna ékspressii gena c-fos v paraventrikuliarnom iadre gipotalamusa u krys.

The effects of intracerebroventricular administration of the non-competitive NMDA-receptor blocker Dizocilpine (MK-801) on delta sleep-inducing peptide (DSIP) suppression of c-fos induction, were studied. The data obtained indicate that preliminary i.c.v. MK-801 injection inhibits immediate early gene c-fos suppression by DSIP in the parvocellular paraventricular hypothalamus.

Behavioral analysis of the consequences of chronic blockade of NMDA-type glutamate receptors in the early postnatal period in rats.

Considering data on the possible glutamatergic nature of the pathogenesis of schizophrenia, we attempted to model cognitive derangements in animals by chronic blockade of NMDA glutamate receptors. Wistar rats received daily s.c. injections of the non-competitive NMDA glutamate receptor antagonist MK-801 (0.05 mg/kg) from days 7 to day 49 of postnatal life. One day after the antagonist injections given on days 27 and 28 of life, animals of the experimental group showed decreased levels of spontaneous movement and orientational-investigative activity as compared with controls, where there was no change in the elevated locomotor reaction produced in response to the direct action of MK-801. These animals showed decreases in the level of anxiety (on day 40 of life) and derangement in spatial learning with food reinforcement (days 50-54 of life). It is suggested that early neonatal blockade of NMDA glutamate receptors leads to the development in animals of disturbances to situational perception and assessment of incoming sensory information.