[Study of neuroprotective, antihypoxic and antiamnesic effects of new mixture of tripeptides].

A new mixture of tripeptides (NMT: H-Lys-Asp-Glu-OH, H-Asp-Glu-Pro-OH, H-Asp-Glu-Arg-OH) in doses of 150 and 300 mg/kg per day produces clearly pronounced neuroprotective effect in rats with brain ischemia and decreases neurologic deficiency 1.1 times more effectively than reference drug semax. NMT (10, 50 and 150 mg/kg) had marked antihypoxic effect on mice in hermetic and altitude chamber. NMT in doses of 10 and 50 mg/kg was more effective than semax in hermetic chamber (1.3 and 1.5 times, respectively) and in a dose of 150 mg/kg in altitude chamber (1.9 times). NMT (50 and 150 mg/kg) had also marked antiamnesic effect on model amnesia caused by scopolamine in rats and was more effective (1.5 and 1.4 times, respectively) than semax in equal doses. NMT (50 and 150 mg/kg) also had marked antiamnesic effect on model amnesia caused by maximal electroshock and complex extreme factors in mice and in both doses was 4 times more effective than semax on the first model and in a dose of 150 mg/kg was 2.9 times more effective on the second model. NMT (50 mg/kg) increased the amplitude of transcallosal evoked potential in rat brain by 69% and was more effective than semax in equal dose. Thus, NMT is a promising neurotropic drug with neuroprotective, antihypoxic and antiamnesic activity.

[Investigation into the vestibular protective properties of melatoninergic agents].

Experiments with rats showed that melatonin (2.5 mg/kg) produces a distinct vestibular protective effect excelling promethazine (50 mg/kg) as a reference agent, and also antidepressant agomelatine (5 mg/kg) as another melatoninergic agent. Lusindol, a blocker of MT1/MT2-receptors (2.5 mg/kg), and bicuculline (1.5 mg/kg), a specific GABA-receptors antagonist, weakened the melatonin effect significantly. The results testify mediation of the melatonin action by these receptors. Whole-cell patch clamp in an experiment with convoluted oblongata sections from white nonlinear infant male rats (14-d old) disclosed that melatonin (2 mM) inhibited drastically (29 +/- 3%) the excitatory postsynaptic current caused by depolarization step in neurons of the medial vestibular nucleus. Lusindol (0.1 mM) inhibited the effect of melatonin (2 mM) significantly (71 +/- 6%) which suggests involvement of melatonin MT1/MT2-receptors.

[Effects of vestibuloprotectors mexidol and melatonin on animal cerebellum].

In experiments with cats, air-assisted microinjections of mexidol and melatonin had a direct effect on 71-81% Purkinje cells inducing the inhibitory response 4.2-6.3 times more often than exiting. In case of concurrent action of MK-801 (a specific noncompetitive NMDA-receptor antagonist) the mexidol effect on the spontaneous activity was suppressed fully or abated significantly in 88% Purkinje cells. Lusindol (a specific melatonin MT2- and MT2-receptor antagonist) and GABA-negative bicuculline prevented the inhibiting effect of melatonin fully or abated significantly the spontaneous activity of 86% and 71% Purkinje cells, respectively. This means that melatonin-produced inhibition recruits both melatonin MT1- and MT2-receptors, and also the GABA-ergic component (stimulation of GABAA-receptors). Investigation of rat's cerebellum slices with prolonged survival showed that 5 mM of mexidol inhibited reliably Purkinje cells population responses by 93 +/- 4%; the presence of MK-801 (100 microMM) weakened this effect by 82 +/- 3%. Consequently, mexidol is capable to inhibit strongly the parallel fibers--Purkinje cells synaptic transmission in the rat's cerebellum, whereas MK- 801 abates this effect appreciably.

[Experimental evaluation of actoprotective activity of nitrogen-containing heterocyclic compounds derivatives in extreme conditions].

In experiments on nonlinear male mice the ability of new derivatives of nitrogen-containing heterocyclic compounds to increase the physical working capacity in conditions of hyperthermia, hypothermia and acute normobaric hypoxia and hypercapnia has been investigated. It is established, that pyridine derivative IBHF-11 has more expressed positive action in the said conditions. It provided increase of the working capacity of animals at all kinds of extreme influence, and the value of positive action was comparable, and in conditions of acute normobaric hypoxia and hypercapnia exceeded those at the reference products bemitil and bromantan.

[On the mechanism of ikaron-1 anti-naupathia action].

Pneumomicroinjection of vestibuloprotector ikaron-1 (Russia) in specific neurons of the medial vestibular nucleus (MVN) was studied in cats immobilized by muscle relaxants using microelectrode devices. The original preparation had a direct effect on the majority of MVN neurons (95 %). Thirty four neurons of 37 cells (92 %) developed an inhibitory response, only one cell (3 %) was activated and 2 neurons (5 %) were areactive. Therefore, the inhibitory reaction to the preparation was 34 times more often than excitatory. An investigation of the MVN neurons activity evoked by adequate stimulation of the vestibular apparatus showed that ikaron-1 attenuates the evoked response in 92 % cells. This phenomenon could be behind the ikaron-lantinaupathia action.

[Analgesic effect of succinate-containing preparations].

It was established that mexidol (100 mg/kg, i.v.) in contrast to cytoflavin (1 ml/kg, i.v.) and reamberin (100 mg/kg, i.v.) produced analgesic effect in rabbits by raising pain threshold under electric stimulation of dental pulp. Mexidol (200 mg/kg, i.p.) also raised the nociceptive threshold of the same tail stimulation by in rats (vocalization test). Non-competitive antagonist of NMDA receptor complex, MK-801 (0.1 mg/kg, i.p.), and selective GABAA receptor antagonist bicuculline (1.5 mg/kg, i.p.) decrease the effect of mexidol. Therefore, the antinociceptive effect of mexidol in rats is mediated by the NMDA receptor complex and GABAA receptors. It was also found that mexidol (microiontophoretic application) produced inhibiting effect on spontaneous and evoked (caused by nociceptive electric stimulation of hind paw) activity of neurons (major part) of sensorimotor cortex and ventral posterior thalamic nucleus in rabbits. On the background of MK-801 and GABA blockers (bicuculline and picrotoxin), this action of mexidol was completely prevented or considerably decreased (by almost 80 and 60% of cells, respectively). Therefore, the effect of mexidol on these neurons is realized by inhibiting ion currents through NMDA receptor complex and via GABAA/benzodiazepine receptor complex.

[Comparative study of the influence of succinate-containing preparations on mitochondrial respiration in rat brain cells].

It has been established by polarographic measurements that preparations containing succinate, such as cytoflavin (0.85 mM succinate), mexidol, and amtizol succinate (at a concentration of 0.85 mM) but not reamberin (0.045 mM succinate), nearly equally (by 35-45%) increase oxygen consumption in rat brain mitochondria. On the other hand, malonate - inhibitor of the respiratory complex II (succinate dehydrogenase) of mitochondrial chain suppressed the stimulating effect of these drugs.

[Studies on actoprotective and antihypoxic properties of new succinate-containing benzothiazole derivatives].

Experiments with mice demonstrated that in contrast to the preparations for comparison (mexidol and reference antihypoxant succinate amtisol at a dose of 1-100 mg/kg) new succinate-containing derivatives of benzothiazole BTI-2 (0.5-5 mg/kg), BTI-3 (0.1, 0.5 and 10 mg/kg), 877-4 (0.5 mg/kg) and BTI-5 (0.5 and 1 mg/kg) improved physical performance of animals by 18-56 and 21-39% in the treadmill test and swimming test (positive effect of BTI-4 and -5 only), respectively. In all three models of acute hypoxia (normobaric hypoxic hypoxia with hyperkapnia, histotoxic and hemic) an obvious antihypoxic activity was displayed by BTI-1 and -2 only. In comparison with mexidol and succinate amtizol, positive and stronger effect of these compounds was achieved at significantly lower doses. Therefore, the succinate-containing benzothiazole derivatives have considerable promise as ingredients of performance enhancing antihypoxic and therapeutic compositions.

[Electrophysiological study of the mechanism of mexidol action].

It has been found that mexidol (5 mM) significantly (96 +/- 2%) depressed excitatory postsynaptic current caused by step depolarization in neurons of medial vestibular nucleus of medulla oblongata slices in young (aged 13 - 17 days) male albino rats. In addition, mexidol (2,5 - 5 mM) depressed by 94 +/- 3% excitatory postsynaptic current caused by Shaffer collaterals stimulation of CA1 pyramidal neurons of hippocampal slices in young rats. Complex MK-801 (non-competitive antagonist of NMDA receptors), in contrast to CNQX (competitive AMPA receptor antagonist), considerably decreased the depressant effect of the drug in both brain structures. Therefore, the central favorable effect of mexidol can be mediated by ion mechanisms with glutamate- and GABA-ergic components, primarily by the inhibition of ion currents through NMDA receptor complex.

[Comparative studies of antihypoxic, neuroprotective and analgesic action of succinate-containing drugs].

Experiments with mice showed that, unlike reamberin (100 mg/kg), mexidol (100 mg/kg) and cytoflavin (1 ml/kg) act as antihypoxants in pressure and hermetic chambers but not in case of acute hemic and histotoxic hypoxia. Amtisol succinate (100 mg/kg), a reference antihypoxant, excels the other tried succinate-containing drugs in all models of acute hypoxia except the hermetic chamber. In addition, the neuroprotective action of mexidol (100 mg/kg/d) and cytoflavin (100 ml/kg/d) in rats with induced ischemic stroke which was stronger than that of reamberin and amtisol succinate (100 mg/kg/d). Besides, mexidol (100 mg/kg) but not cytoflavin (1 ml/kg), reamberin or amtisol succinate (100 mg/kg) had a distinct analgesic effect in rabbits. On the neuronal level, mexidol interacts with the GABAA- benzodiazepine-receptor complex in nearly 60% cells and inhibits ion currents through the NMDA-receptor ion channels in nearly 80% neurons.

[Effects of different neuromediators and regulatory peptides on the impulse activity of neurons in the superior vestibular nucleus].

The microelectrode technique and microiontophoresis of physiologically active substances in experiments with cats immobilized with the muscle relaxants made it clear that different classical neuromediators (acetylcholine, norepinephrine, gamma-aminobutyric acid (GABA) and others), as well as regulatory peptides (enkephalins, thyrotropin-releasing hormone (TRH), vasoactive interstitial peptide (VIP), somatostatin (SS) and others) can exert a direct effect on the majority (61 to 100%) of neurons in the superior vestibular nucleus (SVN). The inhibiting effect of enkephalins, VIP and SS on the neurons impulse activity remained essentially unchanged by L-glutamate. Also, enkephalins, VIP and SS were found to amplify the inhibiting action of GABA and glycine. Consequently, these substances can fulfill the role of SVN neuromediators and/or neuromodulators.

[Actiprotective and antihypoxic action of new heteroaromatic antioxidants].

Expernents with mice showed that most of 15 new heteroaromatic antioxidant compounds possess aciprotective and antixopixic properties. Based on results of treadmill and swimming tests, actiprotective action of IBKhF-1, 11 and 14 surpassed greatly bemythil and bromanthane in ordinary conditions. Inhibitor of gluconeogenase tryptophan cancelled largely the stimulatting action of highly effective and active IBKhF-1, 2 and 11 on physical performance during treadmill exercise. Consequently, gluconeogenesis activation is one of the major components of the actiprotective action of these antioxidants. In addition, IBKhF-1, 11 and 14 excelled bemythil and bromanthane in the extreme conditions of running in hyperthermia and swimming in acute hypoxia combined with hypercapnia. IBKhF-2 and 14 were better than amtisol (standard antihypoxic agent) and bemythil against acute hypoxia in pressure chamber, whereas IBKhF-4 and 14 excelled these agents in thermal chamber.

[Investigation of anti-hypoxic action of 3-hydroxypyridine derivatives in animals with some types of experimental pathology].

Experiments with occlusion of the common carotid artery in mice demonstrated that, unlike mexidol and SK-170, single injection of new derivatives of 3-hydroxypyridine (3-HP) SK-100 and IBKhF-2, and semax have an anti-hypoxic action on the model of acute normobaric hypoxia with hypercapnia. In analogous experiments with rats the distinct anti-hypoxic action was produced by 4 new 3-HP derivatives (SK-100, SK-170, IBKhF-22 at the dose of 100 mg/kg and IBKhF-2 at the doses of 10 and 30 mg/kg--extension of life span by 25-39%), mexidol (100 mg/kg) and reference-class antihypoxant amtisol (30 mg/kg, life span expansion by 19 and 27%, respectively). A series of experiments with rats with acute pancreatitis, a distinct anti-hypoxic action was shown by SK-100, SK-170 at 100 mg/kg and IBKhF at 10 and 30 mg/kg (life span extension by 26-40%), mexidol (100 mg/kg) and amtisol (30 mg/kg) which extended life span by 17 and 22%, respectively. Therefore, SK-100 and IBKhF-2 are potent to prolong life span of equally mice and rats; SK-170 and mexidol were effective only in experiments with rats.

[On the mechanism of antimotion sickness effects of mexidol].

The path-clamp method used within the whole-cell configuration in experiments with convoluted medullar oblongata sections obtained from white mongrel male rats aged 13 to 17 days evidenced that 5 mV of mexidol caused 96 +/- 2% inhibition of the excitation postsynaptic current in neurons of the medial vestibular nucleus generated by the depolarization step of 10 mV (holding potential = -70 my). This means that the antimotion sickness effect of mexidol has its origin in the ion mechanisms with involvement of the glutamate- and GABAergic components, primarily inhibition of ion currents through channels of the NMDA-receptor complex.

[Effects of different neuromediators and regulatory peptides on the impulse activity of neurons in vestibular zone-I of the cerebral cortex].

Microelectrodes and micro-iontophoresis of physiologically active substances in experiments with cats immobilized by muscle relaxants made it apparent that different classical neuromediators (acetylcholine, norepinephrine, GABA and others) and regulatory peptides (enkephalins, thyrotropin-releasing hormone, vasoactive intestinal peptide (VIP), somatostatin (SS) and others) are capable to influence directly 68 to 100% of neurons in vestibular zone-I of the cerebral cortex. In the presence of L-glutamate, the inhibiting effect of enkephalins, VIP and SS on the neurons impulse activity was essentially unaltered. Also it was shown that enkephalins, VIP and SS are potent to augment the inhibiting effect of GABA and glycine. Therefore, these substances may have the neuromediator and/or neuromodulator role in this cortical zone.

[Effects of various neuromediators and regulatory peptides on the impulse activity of neurons in the lateral vestibular nucleus].

The myoelectrode technique and microiontophoresis of physiologically active substances were applied to cats immobilized with neuromuscular relaxant to show that the classic neuromediators (acetylcholine, norepinephrine, GABA etc.) and regulatory peptides (enkephalins, TRHs, vasoactive intestinal peptide (VIP), somatostatin (SS) and others) can influence directly most neurons (58 to 100%) in the lateral vestibular nucleus (LVN). Enkephalins, VIP and SS retained largely their inhibitory effect on the neuron impulse activity in the presence of L-glutamate. Also, enkephalins, VIP and SS are able to stimulate or suppress the inhibitory effect of GABA and glycine. Consequently, the substances under study may act as LVN neuromediators and/or neuromodulators.

[Effect of semax and mexidol on brain ischemia models in rats].

It was established that semax and mexidol significantly reduced neurological deficiency and increased the survival in rats with model brain ischemia induced by the bilateral ligation of common carotid arteries. Mexidol exhibited a linear dose-effect relationship (in a range of doses from 30 to 120 mg/kg per day), while the effect of semax decreased with increasing dose (in a dose range from 0.3 to 1.2 mg/kg per day). Preventive course administration of semax and mexidol considerably reduced neurologic deficiency and amnesia in a step-down passive avoidance situation in rats with model brain ischemia caused by gravitation overload.

[Evaluation of antihypoxic and antiamnemonic effects of mexicor in animals].

In experiments with mice closed in airtight and altitude chambers mexicor effectiveness against hypoxia was evident only at the dose of 100 mg/kg; effect was nil against acute hemic and histotoxic hypoxia. The reference antihypoxic substance (amtisol succinate, 25-100 mg/kg) excelled mexicor in all models of acute hypoxia. In the model of cerebral infarct in rats, the mexicor neuroprotective effect at the doses from 12.5 to 100 mg/kg was dose-dependent with a nearly linear trend and significantly stronger as compared to amtisol succinate. In amnesia models in mice the antimnemonic effect of the drug at the dose of 50-100 mg/kg was much stronger than of amtisol succinate and comparable to commonly used pyracetam and oxiracetam. Mexicor (5 mM per 53 +/- 4%, 10 mM per 94 +/- 6%) inhibited the orthodromic population response in survival sections of hippocampal CA1 in rats. Stimulation of respiration of isolated mitochondria from rat's cerebral cells showed linear dose dependence in the range from 1 mM to 5 mM. It can be concluded that the antihypoxic, neuroprotective and antiamnemonic action is achievable with high mexicor dosage.

[Modification by various neuromediators and regulatory peptides of the impulsation activity of neurons in the medial vestibular nucleus].

Cats were immobilized with myorelaxation agents to apply the microelectrode technique and microlonophoresis of physiologically active substances. As a result it was shown that various classic neuromediators (GABA, taurine and others) and regulatory peptides (vasoactive intestinal peptide (VIP), somatostatine (SS) and others) have effect on the majority (62 to 100%) of neurons in the medial vestibular nucleus. In the presence of L-glutamate VIP and SS CC retained essentially their inhibitory effect on the neurons impulse activity. Both VIP and SS were found to amplify the inhibitory action of GABA and glycine. To sum up, the substances under study can function as neuromediators and/or neuromodulators in the medial vestibular nucleus.