A. T. Proshin

Neurogenesis enhancer RO 25-6981 facilitates repeated spatial learning in adult rats.

The effects of Ro 25-6981 (selective NMDA receptor blocker) in a dose stimulating neurogenesis on repeated learning, reversal learning, and memory reconsolidation were studied in adult rats in Morris water maze. Ro 25-6981 facilitated repeated learning 13 days after injection, but did not influence reversal learning. The blocker injected directly before reminder did not disturb repeated learning and reversal learning in Morris water maze. These effects of Ro 25-6981 on the dynamics of repeated learning seemed to be due to its effects on neurogenesis processes in adult brain.

Hexapeptides HLDF-6 and PEDF-6 restore memory in rats after chronic intracerebroventricular treatment with β-amyloid peptide Aβ(25–35)

Effects of homologous peptides HLDF-6 and PEDF-6 on behavior of animals with experimental Alzheimer’s disease induced by chronic intracerebroventricular administration of β-amyloid peptide Aβ(25–35) were studied in the zoosocial recognition test and Morris water maze. Peptides HLDF-6 and PEDF-6 possessed neuroprotective activity and counteracted the toxic effect of Aβ(25–35). Peptides HLDF-6 and PEDF-6 mainly improved long-term memory and working memory, respectively.

Different Mechanisms of Protective and Differentiative Activities of Homological Peptides TGENHR and TQVEHR

Previously we identified a six-membered fragment 354TQVEHR359 of the C-terminal part of the PEDF (Pigment Epithelium-Derived Factor) differentiation factor molecule that shares homology with fragment 41TGENHR46 of the HLDF (Human Leukemia Differentiation Factor) differentiation factor molecule, which is responsible for its differentiation activity. HLDF has been isolated from the culture medium of human promyelocytic leukemia cell line HL-60. Hexapeptides HLDF-6 (TGENHR) and PEDF-6 (TQVEHR) corresponding to these HLDF and PEDF molecule fragments, which were previously shown to induce cell differentiation (Kostanyan et al. (2000) Russian Journal of Bioorganic Chemistry, 26, 505-511), also have neuroprotective properties. Both peptides prevent degeneration of Purkinje cells of rat cerebellar vermis upon chemical hypoxia induced by sodium azide in vivo; this effect is also observed on a behavioral level. Peptide HLDF-6 but not PEDF-6 promotes survival of HL-60 cells upon chemical hypoxia. Peptides HLDF-6 and PEDF-6 affect different second messenger biosynthesis systems in HL-60 cells. HLDF-6 diminishes cyclic AMP level in those cells due to adenylate cyclase inhibition, while PEDF-6 inhibits phosphatidylinositol-specific phospholipase C stimulated by aluminum tetrafluoride anions.

Irreversible Amnesia in Rats and Edible Snails under Conditions of Associative Memory Reconsolidation Disturbance Caused by NMDA-Glutamate Receptor Antagonist

The effect of MK-801, an antagonist to NMDA-glutamate receptors, on reconsolidation of olfactory discrimination task in rats and taste discrimination in edible snails was examined. Twenty-four hours after conditioning, the animals received a single systemic injection of MK-801 followed by a reminding conditional stimulus. Disturbances in retrieval of the acquired task were observed 10 days after injection followed by a reminding procedure. Repeated conditioning of these animals did not restore the task. Injection of MK-801 without reminding stimulation had no effect on task retention. Thus, disturbances of NMDA-dependent reconsolidation of the associative memory in animals of different taxonomic groups irreversibly eliminated long-term memory.

Corrective effect of flavonoid-containing preparation Extralife on the development of Parkinson's syndrome.

Oral administration of flavonoid-containing preparation Extralife (daily dose 40 mg/kg) to animals with modeled Parkinson’s syndrome considerably improved their survival and the main diagnostic and nosological parameters characterizing the state of locomotor functions. The preparation decreased animal mortality, rigidity, disturbances in dynamic muscular work and coordination of movements, and reduced oligokinesia. Experimental data confirm the involvement of mitochondrial enzyme complex I dysfunction in the pathogenesis of the disease and showed the possibility of by-passing this site of the respiratory chain with Extralife.

Neuroprotective effect of the hexapeptide HLDF-6 on rat hippocampal neurons on the in vivo and in vitro models of alzheimer’s disease

The neuroprotective effect of Thr-Gly-Glu-Asn-His-Arg hexapeptide (HLDF-6), a biologically active fragment of the differentiation factor of human leukemia cells (HLDF), was demonstrated on models of Alzheimer’s disease in vivo and in vitro. The syndromes of this pathology were induced in male rats by injection of beta-amyloid peptide (25–35) and ibotenic acid into the hippocampus. HLDF-6 prevented loss of long-term memory and decrease in the exploratory behavior of these animals and significantly decreased the number of pyknotic neurons in the CA1 area of the hippocampus. This peptide also exerts a protective effect in vitro on the primary cultures of the rat hippocampal and cerebellar neurons under conditions of the beta-amyloid toxicity. An increase in the dihydrotestosterone (DHT) content was demonstrated in the blood plasma of rats with the syndrome of Alzheimer’s disease and in the medium of the culture of hippocampal neurons in the presence of the Aβ(25–35) peptide. HLDF-6 inhibited this increase in both cases. A probable mechanism of the neuroprotective effect of HLDF-6 was suggested as being connected to its possible effect on both the biosynthesis and the metabolism of sex steroid hormones.

Different populations of neurons in relevant brain structures are selectively engaged in the functioning of long-term spatial memory

Using immunohistochemical methods, we studied the expression of the c-fos transcription factor in cells that synthesize the neuron-specific proteins NeuN and calbindin D-28K in the hippocampus, cerebellar vermis, and motor and retrosplenial cortex after training to find a hidden platform in a water maze. We also found apoptotic neural cells that expressed NeuN. We observed significant differences between trained and control rats in the intra- and interstructural distribution of the NeuN- and calbindin-positive neurons that expressed c-fos. We found a correlation between the number of c-fos-expressing NeuN-positive neurons in the retrosplenial cortex and indicators of long-term spatial memory consolidation. We believe that the data we obtained reflect the selective engagement of neurons from different neural populations in relevant brain structures in the functioning of long-term spatial memory.

Delayed Effects of NMDA Receptor Antagonist MK-801 on Storage and Reconsolidation of Spatial Memory in Rats

We studied the effects of NMDA receptor antagonist MK-801 on the storage and reconsolidation of spatial memory in Morris water maze in adult rats. MK-801 (50 μg/kg) administered 24 h after the completion of training was shown to improve the resistance of spatial memory to spontaneous extinction, while reminder against the background of MK-801 suppresses its ameliorating effect on memory storage. The detected behavioral effects of MK-801 persisted over 60 days after administration and can be associated with its influence on coupled neurogenesis/apoptosis processes induced during memory trace formation in adult animals.

Neurogenesis and apoptosis in the mature brain during formation and consolidation of long-term memory

We measured the contents of the cell proliferation marker 5-bromo-2′ deoxyuridine (BrdU) in native and fragmented DNA (indicators of neoneurogenesis and neoapoptosis) in the cerebral cortex, hippocampus, and cerebellum of adult rats, as well as a marker of apoptosis, the internucleosomal DNA fragmentation at 1, 14, and 30 days after systemic administration of BrdU, which coincided with the beginning of a 4-day training in the Morris watermaze. We found that physical exercise and the emotional condition associated with swimming in the pool induced a substantial increase (more than two-fold) in the level of neoneurogenesis and neoapoptosis markers in all explored rat brain structures. The initial stage of long-term memory formation triggered a significant increase in apoptotic activity in the hippocampus and cerebellum. The consolidation of long-term spatial memory is associated with significant changes in indicators of differentiation and programmed cell death of new 14–30-day-old cells in the prefrontal cortex and cerebellum. We demonstrated the differences in the power and direction of correlations between proliferation, differentiation, and loss of “new” and “old” cells in the studied adult brain structures during physical exercise and the formation of long-term memory.

A Hardware-and-Software System for Experimental Studies of the Acoustic Startle Response in Laboratory Rodents.

We developed and tested a novel hardware-and-software system for recording the amplitude of the acoustic startle response in rodents. In our experiments, the baseline indexes of acoustic startle response in laboratory rats and pre-stimulation inhibition under the standard delivery of acoustic stimulation were similar to those evaluated by other investigators on foreign devices. The proposed system is relatively cheap and provides the possibility of performing experiments on freely moving specimens. It should be emphasized that the results of studies can be processed with free-access software.