[The study of procognitive effect of the potential antipsychotic, Dilept and its main metabolite, GZR-125 at the novel objects recognition test in rats].

The effect of dipeptidal neurotensine mimetic, N-caproyl-L-prolyl-L-tyrosine methyl ester (GZR-123, Dilept) and its main metabolite N-caproyl-L-prolyl-L-tyrosine (GZR-125) was evaluated at novel objects recognition test (NOR) in the male outbred rats. NOR was chosen from many cognitive test as those involving the selective action on the attention and episodic memory and considering as translational model for the study of cognition deficiency in schizophrenics. M-cholinoblocking agent scopolamine (0.2 mg/kg s.c.) was used as agent disturbing the performance of the test. Dilept (2 mg/kp i.p.) was shown to restore the NOR performance, disturbed by scopolamine. The same was true for GZR-125 (2 mg/kp i.p.), whose cholinopositive effect could contribute to the procognitive effect of the parent molecule.

[The efficacy of human NGF dipeptide mimetic on the streptozotocin-induced model of diabetes in rats].

The effect of a new dimeric dipeptide mimetic GK-2 of the loop-4 human NGF (hexamethylendiamide-bis-N-monosuccinyl-glycil-L-lysine) was investigated for the first time on the dynamics of hyperglycemia and body weight loss caused in Wistar rats by streptozotocin (45 mg/kg i.p.) Prophylactic (2 weeks before streptozotocin) daily administration combined with therapeutic (4 weeks after STZ) administration of GK-2 (0.1 mg/kg i.p.) was shown to attenuate significantly the degree of hyperglycemia and to reverse the streptozotocin-induced weight loss.

[Hypocoagulant effect of the novel dipeptide NGF mimetic GK-2].

The effect of an original dimeric dipeptide NGF mimetic, GK-2 (hexamethylenediamide bis-N-monosuccinyl-L-glutamyl-L-lysine, designed on the basis of the beta-turn of the 4th NGF loop) on the hemostasis and fibrinolysis was studied in intact and diabetic Wistar rats in various periods of disorder development. Model diabetes was induced by single streptozotocin (40 mg/kg i.p.) administration. Blood glucose level, main parameters of thromboelastograms, and euglobulin clot lysis time were measured. The effect of GK-2 was studied under ex vivo conditions, by adding freshly prepared peptide solution to the blood plasma. The maximum increase in the thrombosis probability was observed in ten days after streptozotocin injection, as manifested by an increase in coagulation indices CI and I together with a decrease in the euglobulin clot lysis time. Adding GK-2 (10(-5) M) to the blood plasma was found to normalize these parameters. The tendency to hypocoagulant effect was also observed in experiments with GK-2 adding to the blood plasma of intact animals. The hypocoagulant effect of GK-2 in combination with its antihyperglycemic effect (revealed previously) is of great importance, since diabetes is known to be accompanied by violated microcirculation and increased risk of thrombosis.

[Neuroprotective effects of a dipeptide mimetic on the GK-2 nerve growth factor in model of permanent common carotid artery occlusion in rats].

The behavioral and biochemical effects of a new dipeptide mimetic of the GK-2 nerve growth factor (NGF) have been studied on a model of chronic cerebral ischemia induced by permanent common carotid artery occlusion in rats. It is established that subchronic intraperitoneal injections of GK-2 (0.5 mg/kg) 4 h after surgery, followed by seven more injections made every 24 h, fully prevent the death of operated animals and reduces the development of habitation deficit (open-field test) and decrease in exploratory activity (novel object examination) two weeks after surgery, as well as fully restores the viability of cerebral cortex cells and decreases the hyperexpression of HSP70 in cerebral cortex.

[The search of small molecules with antipsychotic activity on the background of neurotensin].

Tridecapeptide neurotensin (NT) is known to exert the neuroleptic-like effects in case of its intracerebral administration. The group of systemically active dipeptides , acylprolyltyrosines, was constructed on the background of NT. Methyl ester of N-caproyl-L-prolyl-L-tyrosine (Dilept) was chosen for further development. The paper is dealing with main principles of Dilept'design and with analysis of the experimental data concerning its effect on the "translational" model of schizophrenia--the deficit of prepulse inhibition of the acoustic startle-reaction caused by either dopamine-mimetic, apomorphine, or by the uncompetitive NMDA-blocker, ketamine. Dilept was shown to attenuate these deficits both in case ofintraperitoneal and peroral administration. Dilept is considered as a potential antipsychotic.

[Effect of the novel nootropic and neuroprotective dipeptide noopept on the streptozotocin-induced model of sporadic Alzheimer disease in rats].

Streptozotocin-intracerebroventricularly treated rats are proposed as an experimental model of sporadic Alzheimer disease (AD). Diabetogenic toxin streptozotocin (STZ) administered in both cerebral ventricles in a dose of 3 mg/kg decreases the expression of NGF and BDNF mainly in the hippocampus and increases the content of malonic dialdehyde (MDA)--a product of lipid peroxidation--in the brain tissues. These metabolic changes are accompanied by a pronounced cognitive deficiency, which is manifested by long-term memory deterioration in the passive avoidance test. These manifestations of pathology are not accompanied by hyperglycemia in the case of intraventricular STZ administration, in contrast to the systemic (in particular, intraperitoneal) route of introduction that causes a pronounced increase in the blood glucose level. These results are consistent with the existing notions that (i) STZ administered intraventricularly provokes a complex of changes imitating the sporadic AD and (ii) this disease can be considered as a manifestation of type-III diabetes. The new original cognition enhancing and neuroprotective dipeptide noopept decreases the aforementioned metabolic changes and the accompanying long-term deterioration of the memory. Previously, this systemically active dipeptide was shown to be capable of increasing expression of NGF and BDNF in the hippocampus, stimulating the antibody production to beta-amyloid, inhibiting the lipid peroxidation, activating the endogenous antioxidant systems, and decreasing the rate of glutamate release (cholinopositive effect). Taken together, these data indicate that noopept can be considered as a multipotent substance acting upon several important pathogenic chainsof the sporadic AD.

[On the mechanism of noopept action: decrease in activity of stress-induced kinases and increase in expression of neutrophines].

The influence of noopept (N-phenylacetyl-L-prolylglycine ethyl ester, GVS-111)--a drug combining the nootrope and neuroprotector properties--on the activity of mitogen-activated protein kinases (MAPKs) and the level of NGF and BDNF gene and protein expression in the frontal cortex, hippocampus, and hypothalamus has been studied in rats. Under conditions of chronic administration (28 days, 0.5 mg/day, i.p.), noopept decreased the activity of stress-induced kinases (SAPK/JNK 46/54 and pERK1/2) in rat hippocampus and increases the level of mRNA of the BDNF gene in both hypothalamus and hippocampus. The content of BDNF protein in the hypothalamus was also somewhat increased. In the context of notions about the activation of stress-induced kinases, as an important factor of amyloidogenesis and tau-protein deposition in brain tissue, and the role of deficiency of the neurotrophic factors in the development of neurodegenerative processes, the observed decrease in the activity of stress-activated MAPKs and increased expression of BDNF as a result of noopept administration suggest thatthis drug hasaspecific activity withrespect to some pathogenetic mechanisms involved in the Alzheimer disease.

[Effect of dipeptide neurotensin analog dilept on extracellular concentrations of glutamate, GABA and HVA in N. accumbens of rat brain].

The influence of dilept (GZR-123, N-caproyl-L-prolyl-L-tyrosine methyl ester)--a dipeptide analog of neurotensin (NT)--on extracellular concentration of glutamate, gamma-aminobutyric acid (GABA) and homovanillic acid (HVA) in n. accumbens of Wistar rats has been studied. By means of microdialysis, it was shown that dilept increases the concentrations of glutamate and GABA and decreases the HVA content in n. accumbens. These effects of dilept are similar to those produced by NT introduced into n. accumbens. Thus, dilept can be considered as a systemically active dipeptide analog of NT, which is capable of modulating the dysbalance of glutamate-, GABA-, and dopaminergic systems of n. accumbens. These neurochemical data taken together with previously established behavioral effects of dilept suggest that this dipeptide is a potential antipsychotic drug.

[Neurotensine dipeptide analog dilept decreases the deficiency of prestimulus startle reflex inhibition: a prognostic sign of antipsychotic activity].

The antipsychotic properties of dilept, a new drug representing substituted dipeptide based on a beta-rotational structure of the main metabolite of endogenous neuroleptic NT8-13, have been studied using the test for prestimulus inhibition (PSI) of the acoustic startle reflex in rats. It is established that dilept eliminates the PSI deficiency caused by the introduction of a noncompetitive NMDA receptor blocker ketamine, which is evidence for pronounced neuroleptic properties of the drug. Effective doses of dilept for intraperitoneal administration were 1.6, 3.2, and 6.4 mg/kg, the maximum antipsychotic effect being produced at 1.6 mg/kg. Dilept also prevented the PSI deficiency upon peroral administration in rats. In this case, the drug administration per os in the form of a tabletization mixture with poly(vinyl pyrrolidone) and lactose was more effective compared to a mixture of the parent substance with Tween-80, which can be explained by the favorable effect of additives on the bioavailability of dilept. The maximum antipsychotic effect of dilept upon oral administration was observed for a dose of 16 mg/kg. The ability of dilept to eliminate the PSI deficiency in the acoustic startle reflex test on the model of glutamate-negative psychosis in rats can be considered as a prognostic sign for the drug efficiency with respect to the negative and cognitive symptoms of schizophrenia and autism manifestations. The antidopamine activity of dilept allows us also to predict the drug efficiency with respect to the positive manifestations of schizophrenia.

[Experimental pharmacokinetics of the new neurotensine-derived antipsychotic drug dilept].

The metabolism and pharmacokinetics of a new neurotensine-derived dipeptide drug dilept (N-caproyl-L-prolyltyrosine methyl ester) and its tentative metabolites after intravenous and peroral administration of the parent drug and its tabletized form in rats have been studied by HPLC-ESI(-)-MS/MS method. It is established that unchanged dilept (detected in the blood plasma for no less than 30 min) as well as N-caproyl-L-proline and N-caproyl-L-prolyl-L-tyrosine (both detected in the blood over more than 4 h) are the major metabolites in the bloodstream upon peroral administration of the drug. The proposed structures of metabolites were confirmed by countersynthesis. Dilept and N-caproyl-L-prolyl-L-tyrosine penetrate through the blood - brain barrier. The drug is rapidly absorbed, distributed, and metabolized in the rat organism. Peroral administration of dilept in rats in the form of tablets (at a dose of 200 mg/kg) resulted in a significant increase in intestinal absorption, as evidenced by a 22% improvement in the bioavailability, whereas dilept alone showed an absolute bioavailability of less than 1%.

[The original nootropic and neuroprotective drug noopept potentiates the anticonvulsant activity of valproate in mice].

The influence of the original dipeptide drug noopept, known to possess nootrope, neuroprotector, and anxiolytic properties, on the anticonvulsant activity of the antiepileptic drug valproate has been studied on the model of corazole-induced convulsions in mice. Neither a single administration of noopept (0.5 mg/kg, i.p.) nor its repeated introduction in 10 or 35 days enhanced the convulsant effect of corazole, which is evidence that noopept alone does not possess anticonvulsant properties. Prolonged (five weeks) preliminary administration of noopept enhanced the anticonvulsant activity of valproate. This result justifies the joint chronic administration of noopept in combination with valproate in order to potentiate the anticonvulsant effect of the latter drug. In addition, the administration of noopept favorably influences the cognitive functions and suppresses the development of neurodegenerative processes.

[Interstrain differences in the content of excitatory and inhibitory amino acids in the brain of DBA/2J, Balb/c and C57BL/6 mice: characteristics of the effect of a dipeptide antipsychotic drug dilept].

We have performed a comparative study of the content of glutamate (Glu), aspartate (Asp), taurine (Tau), glycine (Gly) and gamma-amino-butyric acid (GABA) in the cortex, hippocampus, and striatum of the DBA/2J, Balb/c and C57BL/6 mice brain. The levels of Glu, Tau and GABA in DBA/2J hippocampus was lower than those in other experimental strains. These findings are consistent with published data on the specific neurophysiological properties of DBA/2J (neuroleptic sensitive prepulse inhibition, deficit), thus allowing this strain to be used in modeling schizophrenia. Taking into account these facts, in the next step we investigated the effects of dilept, the new neurotensine-derived dipeptide with antipsychotic activity (GZR-123, methyl ester of N-caproyl-L-prolyltyrosine), on the content of neurotransmitter acids in DBA/2J mice brain structures. In a dose of 0.8 mg/kg (i.p.) dilept induced a statistically significant increase in the levels of Glu, Tau and GABA in striatum of DBA/2J, as well as insignificant increase in the levels of these amino acids in the cortex. These effects are quite similar to those described for the parent peptide neurotensine, in case of its intracerebral administration. The results of our study prove the necessity of the further development of dilept as a potential antipsychotic drug.

[Behavior of mice from different strains: modifications produced by noopept].

Genotype-dependent behavioral effects were demonstrated in BALB/c, C57BL/6J [Russian character: see text] DBA/2J mice after injections of nootropic drug Noopept. In an elevated plus maze, drug administration induced an increase in the number of enterings into bright arms in BALB/c mice, whereas the opposite effect was observed in C57BL/6J. After the Noopept administration, animals from all the three strains increased the number of active avoidance reactions in stress-inducing slip-funnel test. A significant intensification of exploration behavior was observed in a closed plus-maze in BALB/c and C57BL/6J. The Noopept affected weakly or had no effect on the behavior of DBA/2J mice.

[Decrease in the glutamate release may contribute to the neuroprotective action of the novel neuroleptic drug dilept].

Dilept (GZR-123, N-caproyl-L-prolyl-L-tyrosine methyl ester), designed and synthesized at the Zakusov Institute of Pharmacology, was chosen as one of the most effective compounds from a series of N-acylprolyltyrosine derivatives having common pharmacophores with beta-turn of neurotensin (NT(8-13)) and repeating the structure of a nonpeptide prototype, the atypical neuroleptic sulpiride. The aim of this study was to evaluate the effect of dilept on the level of spontaneous and K(+)-stimulated release of glutamate. The experiments were performed in vitro on the cortical brain slices of male Wistar rats. Dilept used in concentrations 10(-5) and 10(-6) mole/liter did not affect the spontaneous release of glutamate though markedly decreased the K(+)-stimulated release. A decrease in the glutamate release under the action of the neuroleptic could contribute to the neuroprotective activity of dilept.

[Analysis of passive avoidance learning in a modified three-compartment setup].

Passive avoidance conditioning is analyzed in a three-compartment apparatus comprising the central light compartment, the dark dangerous compartment in which the electric foot shock was delivered, and the dark safe compartment where the rats were not punished. The passive avoidance performance was characterized, in addition to the latent period duration, by the number of visits into the safe compartment. The experimental data indicate that the latency of the passive avoidance response and the safe compartment preference obey different laws. The latency depends linearly on the number of shocks, while neither the safe compartment preference nor its relation to the number of shocks was observed. Piracetam had no effect on the latency, but enhanced the number of visits into the safe compartment. It is concluded that this modified model may be useful in an analysis of nootropic effects of neuropsychotropic substances.

[Genotype-dependent mice behavior in cognitive tasks. Effect of noopept].

The interstrain differences in performance of C57BL/6J, BALB/c and DBA/2J male mice in two cognitive tasks were found. Mice C57BL/6J showed good learning ability and preservation of memory traces tested 10 days after performance in a simplified version of Morris water maze. Mice BALB/c learned the task but, virtually, no long-term memory traces were revealed, whereas DBA/2J demonstrated poor learning. The effect of nootropic drug Noopept (GVS-111, N-phenil-acetyl-L-prolylglycin ethyl ether) was shown to be genotype-dependent. Its administration (0.5 mg/kg i.p., 15 min before learning) improved the long-term memory in Morris test in BALB/c mice but failed to produce any improvement in C57BL/6J. The ability of mice for extrapolation of the direction of stimulus movement differently changed after Noopept injections: the proportion of correct task solutions increased in C57BL/6J and BALB/c mice, whereas the performance of DBA/2J did not change.

[Neuroprotective activity of the proline-containing dipeptide noopept on the model of brain ischemia induced by the middle cerebral artery occlusion].

The influence of noopept (N-phenylacetyl-L-prolylglycine ethyl ester, GVS-111) on the extent of ischemic cortical stroke was investigated in experiments on white mongrel male rats with ischemia induced by a combination of the middle cerebral artery occlusion with ipsilateral common carotid artery ligation. Animals were treated with noopept (0.5 mg/kg, i.p.) according to the following schedule: 15 min and 2, 24, and 48 h after the occlusion. Test rats were decapitated 72 h after occlusion, brains were extracted and frozen, and thin brain slices were stained with 2,3,5-triphenyltetrazolium chloride. The slices were scanned and processed using Auc 1 computer program, which estimates the percentage of damaged area relative to that of the whole ipsilateral hemisphere. The conditions of coagulation the distal segment of middle cerebral artery were selected, which caused necrosis localized in the fronto-parietal and dorso-lateral regions of the brain cortex without any damage of subcortical structures. The extent of the brain damage in control group (treated by saline) was 18.6%, while that in the group treated with noopept was 12.2%, thus demonstrating a decrease in the infarction area by 34.5% (p < 05). The data on noopept efficacy on the model of the extensive ischemic injury of brain cortex show that this drug has good prospects for use in the neuroprotective treatment of stroke.

[Noopept improves the spatial memory and stimulates prefibrillar beta-amyloid(25-35) antibody production in mice].

The effects of the novel proline-containing nootropic and neuroprotective dipeptide noopept (GVS-111, N-phenylacetyl-L-prolylglycine ethyl ester) were studied on NMRI mice upon olfactory bulbectomy, which had been previously shown to imitate the main morphological and biochemical signs of Alzheimer's disease (AD). The spatial memory was assessed using the Morris (water maze) test; the immunological status was characterized by ELISA with antibodies to prefibrillar beta-amyloid(25-35), S100b protein, and protofilaments of equine lysozyme, which are the molecular factors involved in the pathogenesis of AD. The control (sham-operated) animals during the Morris test preferred a sector where the safety platform was placed during the learning session. Bulbectomized animals treated with saline failed to recognize this sector, while bulbectomized animals treated with noopept (0.01 mg/kg for 21 days) restored this predominance, thus demonstrating the improvement of the spatial memory. These animals also demonstrated an increase in the level of antibodies to beta-amyloid(25-35)--the effect, which was more pronounced in the sham-operated than in bulbectomized mice. The latter demonstrated a profound decrease of immunological reactivity in a large number of tests. Noopept, stimulating the production of antibodies to beta-amyloid(25-35), can attenuate the well-known neurotoxic effects of beta-amyloid. The obtained data on the mnemotropic and immunostimulant effects noopept are indicative of good prospects for the clinical usage of this drug in the therapy of patients with neurodegenerative diseases.

[Dilept: a tripeptoid neurotensin analog combining neuroleptic activity with positive mnemotropic action].

The effect of N-caproyl-L-prolyl-L-tyrosine methyl ester (GZR-123, Dilept), a new antipsychotic drug with a dipeptide structure, on cognitive functions was studied using the passive avoidance conditioned reflex (PACR) test. It was found that the drug improved both the acquisition and retrieval of PACR under the conditions of undertraining and prevented the amnesic effect of transcorneal electroshock. The neurotransmitter analysis of these effects using the corresponding blockers showed the ability of dilept to facilitate the central glutamatergic (NMDA type) and cholinergic (of both muscarine and nicotine types) neurotransmission. No evidence of the involvement of the GABAergic system was observed. The experimental data on the combination of antipsychotic effect with memory improving activity suggests that dilept may be effective in cases of negative symptoms of schizophrenia and psychotic manifestations in Alzheimer disease.

[The new tripeptoid neurotensin analog dilept selectively affects dopamine turnover in nucleus accumbens and hypothalamus].

The effects of dilept (N-caproyl-L-prolyl-L-tyrosine methyl ester) - a new peptidomimetic of neurotensine - on the level of monoamines and their main metabolites in four functionally important brain structures has been studied upon single and subchronic administration in intact rats and in those pretreated with the NMDA receptor blocker ketamine. Repeated administration of dilept favors the accumulation of DOPAC and accelerates the dopamine (DA) turnover in nucleus accumbens, as manifested by an increase in the DOPAC/DA ratio. The opposite effect (decrease in the DOPAC/DA ratio) was observed in the hypothalamus, where the subchronic treatment with dilept completely inhibited the activating action of ketamine on the DA turnover. The selective influence of dilept on the dopaminergic system activity in nucleus accumbens (but not in striatum), together with the previously obtained behavioral data, suggest that dilept is a new atypical neuroleptic producing no extrapyramidal side effects.