[THE REGULATING EFFECT OF DIPEPTIDES ON CELL PROLIFERATION IN NERVE TISSUE CULTURE IN MAMMALS AND ON ASSOCIATIVE LEARNING IN INSECTS].

The effect of dipeptides AspPro and AspSer and of their composing amino acids (asparagine acid--Asp, proline--Pro, serin--Ser) on the proliferative activity in the explants of cortex and subcortical structures of the rat brain and on the functional activity of CNS of the honeybee was studied. The square index defined as a proportion of the whole explant square to the square of its central zone was determined. The number of bees responded with the conditional reaction (proboscis extension in the direction to aromatized solution) after 1 min (short-term memory) and 180 min (long-term memory) was detected after single learning procedure. Both dipeptides, as well as the asparagine acid, stimulated an increase of the growth zone of the subcortical structure explants in rats and of the number of honeybees with retention of conditional reaction in the short-term/long-term memory independently of the effect of the second member of the dipeptide. The unidirectionality of the effect suggests the existence of common mechanisms of reception and signal transduction established during evolution that require the further study.

[Metabotropic receptor of the group I of the 5th subtype (ImGLuR5) in honeybee associative olfactory learning].

The work deals with study of character of localization in the honeybee head ganglion of metabotropic receptor ImGluR5 and its role in memory formation. With aid of pharmacological method (injections of antisense oligonucleotide and of selective receptor agonist and antagonist) and of behavioral criterion (formation and testing of preservation in memory of conditioned alimentary reflex for olfactory stimulus), there is first shown participation of the studied receptor in formation of the honeybee long-term memory. By using the immunohistochemical method, there is first revealed the predominant expression of the ImGluR5 receptor in the mushroom body Canyon cells responsible for the insect integrative activity. The present study, together with the previous ones, allows concluding about the presence in the honeybee head ganglion of the group I of metabotropic glutamate receptors with two subtypes 1 and 5 (ImGluR1,5) that have similar with mammalian pharmacological properties favoring preservation of the individually acquired experience in the long-term memory.

[On epigenetic regulation of process of formation of long-term memory].

The review summarizes current concepts on role of several covalent posttranslation chromatin modifications in the process of memory formation in vertebrate and invertebrate animals. There is described a chain of intracellular events from activation of receptors and signal pathways to change of the functional state of genome.

[Genetic determinants of generating the motor pattern of rhythmic movements in Drosophila melanogaster].

To investigate molecular and cellular mechanisms of central pattern generators (CPG) functioning, we previously selected candidate genes mutations of which are accompanied with deviations in Drosophila melanogaster motor activity. In this research we tested locomotor parameters in lines with post transcriptional silencing of 12 candidate gene in Drosophila central nervous system. Silencing was provided by synthesis of interfering RNA by means of GAL4/UAS system under control of CNS-specific gene promoters (elav, nrv2, appl, tsh). It was found that RNA interference of most genes are accompanied with changes in one or several locomotor parameters. Pattern of revealed deviations under control of different promotors makes it possible to determine the genes that activity in nervous system is necessary for proper functioning of locomotor CPG.

[Peculiarities of the courtship song in the Drosophila melanogaster populations adapted to gradient of microecological conditions].

In theory of evolution, two chief scenarios of development of sexual isolation--allopatric and sympatric, which act respectively under conditions of geographic separation or without it. Differences in the courtship behavior and in the used signals can lead to reproduction isolation and prevent gene exchange between sympatric populations or species, in which postcopulational barrier are absent. The previous studies of natural Drosophila populations inhabiting the opposite, ecologically contract slopes of evolutional canyon (vicinities of the brook Open in the mountain ridge Karmel, Israel) revealed statistically significant differences between them by the complex of adaptive and behavioral parameters including courtship behavior and choice of partner for copulation. Astonishingly, differentiation of two populations has appeared in spite of a very small distance between two slopes. Here we report the statistically significant differences between males from the opposite slopes in characteristics of the courtship song that is one of signals serving for recognition by female of sexual partner of her species. We suggest that these differences can underlie the earlier revealed female discriminational behavior and can reflect different adaptive strategies in the populations inhabiting opposite canyon slopes.

[Novel memory mutants in Drosophila: behavioral characteristics of the P-insertional mutant in the Ent2P locus].

The Drosophila mutant P124, carrying insertion of P(lacW) vector in the second chromosome on the background of the w mutation in the X chromosome, was previously isolated as showing memory deficiency after courtship conditioning. Here we report additional features of the mutant phenotype: (1) abnormal adaptation to dark-light transition; (2) impaired perception by males of nuances of visual image of a female, specifically, of her fine movements such as preening and ovipositor extrusion; (3) subnormal performance index after odor-shock conditioning. These abnormalities are not related to a deficit of the eye screening pigments because they are also revealed on the background of the normal w+ allele in the X chromosome. The visual and cognitive impairments are independent pleiotropic effects of the mutation. The mutation is caused by insertion of the P vector 12 nucleotides upstream of the transcription start of the gene Ent2 (equilibrative nucleoside transporter 2). Ent2(P124) is the second mutant allele of this gene found in Drosophila. The genetic variability in Ent2 locus should be considered as a factor of risk for development of mental retardation and disorders of visual perception.

Comparative studies of four Drosophila P-insertion mutants with memory defects.

Studies of conditioned reflex courtship suppression in mutant Drosophila males in two tests--a memory retention test (with a virgin female) and a repeat training test (with a fertilized female)--yielded experimental support for a previously suggested physiological model of the acquisition of this reflex. Mutations altered both types of conditioned association suggested in the model, i.e., the association between the conditioned and unconditioned stimuli (lat, rut, dnc, amn, and P153) and the association between the conditioned stimulus and the aversive motivational system mediating the action of the unconditioned stimulus (P171). A third category of mutants appeared to have a disturbance to the function of the aversive motivational system (P95 and P124).

Plasticity of social behavior in Drosophila.

This article presents results obtained from studies of the plasticity of changes in social behavior in Drosophila (interactions between individuals in groups) in conditions of homo- and heterogeneous environments. This is the first report of data illustrating self-starting acquisition by female Drosophila of a classical conditioned reflex to contextual factors signaling possible threats from other individuals and blocking the initiation of activity. A previously described operant conditioned reflex also helped flies avoid aggression from other individuals and make more efficient use of food resources by decreasing the initially high level of activity. Classical conditioning had the effect that the fly did not need to repeat acquisition of the conditioned reflex each time: when placed into an analogous situation, the fly's activity automatically decreased as a result of exposure to the conditioned stimulus, i.e., contextual factors.

[Comparative study of four P-insertional memory-deficient Drosophila mutants]. / Sravnitel'noe izuchenie chetyrekh P-insertsionnykh mutantov drozofily s defektami pamiati.

The previously suggested physiological model of conditioned courtship suppression in Drosophila was experimentally supported through investigation into the behaviour of the mutant males in two tests: the memory retention test and the retraining test. The mutations disrupted both types of the conditioned connections predicted by the model: association between conditioned and unconditioned stimuli and association between the conditioned stimulus and the aversive motivational system mediating the response to the unconditioned stimulus. The third category of mutants (P95, P124) appears to disrupt the function of the aversive motivational system.

Identification of Drosophila mutant with memory defects after acquisition of conditioned reflex suppression of courtship.

Four lines were selected from a collection of 33 lines prepared by P insertion mutagenesis using a single-copy P-element system; the males of these four lines showed memory defects after acquisition of conditioned reflex suppression of courting. In two lines (P171 and P95), the dynamics of retention of the conditioned reflex in the repeated impregnated-female courting test were similar to those of known short-term memory mutants dnc and rut. In line P153, the dynamics were more reminiscent of the memory dynamics in a known medium-term memory mutant, amn. In line P124, the learning index was insignificant immediately after training was completed, which may indicate that this line was unable to acquire conditioned reflex suppression of courting. Determination of the positions of the P elements (P171: 48A-B; P153: 49B-C; P124: 67B-68A; P95: 77C-D) showed no correspondence with previously known mutations producing memory lesions.

[Plasticity of the social behavior in Drosophila]. / Plastichnost' sotsial'nogo povedeniia u drozofily.

Original data illustrate self-starting classical conditioning to environmental factors in Drosophila, the factors serving as signals of a possible threat from other individuals and blocking initiation of activity. Instrumental conditioning resulting in reduction of an initially high level of activity in the group situation, helps a fly to avoid aggression from other flies and to use the food resources more efficiently. Classical conditioning makes it unnecessary for a fly to learn this instrumental task again and again: being faced with an analogous situation the fly automatically decreases its activity following presentation of the conditioned stimuli or the specific environment.

[Isolation of memory-deficient Drosophila mutants in conditioned courtship suppression paradigm]. / Vyiavlenie mutantov drozofily, proiavliaiushchikh defekty pamiati posle vyrabotki uslovnoreflektornogo podavleniia ukhazhivaniia.

Among 33 mutant stocks of Drosophila melanogaster generated by means of P-insertional mutagenesis in the system with single P element, 4 stocks have been isolated as demonstrating deficient memory in the conditioned courtship suppression paradigm. Localization of the P insertions never coincided with that of previously known mutations affecting memory.

Age-dependent changes in memory and mushroom bodies in the Drosophila mutant vermilion deficient in the kynurenine pathway of tryptophan metabolism.

Evolutionary conservation of homologous genes that cause related phenotypes in humans and Drosophila help to unravel genes implicated in polygenic human diseases. Among them are neurodegenerative disorders, such as Huntington, Parkinson, Alzheimer and HIV-induced diseases. They are characterized by a late onset disturbances of memory, changes in volumetric indices of the brain structures involved in memory formation, synaptic and glial pathology, and altered content of the intermediates of the kynurenine pathway, the endogenous modulators of the NMDA receptors. This pathway in conserved in insects, rodents and humans. We, therefore, studied the effects of aberrant tryptophan metabolism on memory, brain plasticity, synaptic and glial immunoreactivity in the Drosophila mutants vermilion (no kynurenines) and cinnabar (excess of neuroprotective kynurenic acid) over the life time. The mutant vermilion demonstrated gradual decline of 3-th memory performance and complete memory failure on the 28th day of life in a paradigm of conditioned courtship suppression. A drastic increase in the volume of the calyces of the mushroom bodies, and a decay in immunochemical staining of this brain structure with antibodies to synaptic protein csp and glia, precede the age-dependent memory defect and develop from the 12th day of adult life.

Drosophila conditioned courtship: two ways of testing memory.

In Drosophila, courtship reduction in male flies that have previous experience of courting a mated female is a result of the counterconditioning of an attractive unconditioned stimulus (US)--the aphrodisiac--which becomes an aversive conditioned stimulus (CS) after being paired with an aversive US--the antiaphrodisiac. In a retention test with a virgin female lacking the antiaphrodisiac, males retain a lower level of courtship for 3 hr after training. However, a measure of courtship suppression, the learning index (LI), decreases significantly after only 1 hr. In contrast, in the retraining test with a mated female, the LI shows no decrease for 8 hr but falls below significance 16 hr after training. These results are discussed in terms of the transfer of training. Nonspecific transfer and nonassociative behavioral modifications play little, if any, role in the transfer of training. The retraining test is recommended as a new protocol for studying conditioned courtship. According to the model proposed here, in tests with a virgin female, the duration of memory retention is limited by the retention of the direct association between the CS and the aversive motivational system or by the retention of an internal representation of the US. In retraining tests, the CS-US association seems to be the only factor involved in transfer 3 or more hours after training.

Genetic aspects of the mechanisms of learning.

Published data demonstrating the direct involvement of the genome in processes associated with learning are presented. These processes include the intensification of protein and RNA synthesis during learning and induction of early gene expression during learning. The relationship between consolidation of memory traces and protein synthesis is discussed. Along with different types of memory needing induction of gene expression for consolidation, some types of long-term memory are independent of protein synthesis. The use of genetic methods for studying the mechanisms of learning and memory is discussed.

Autosomal mutations in Drosophila which reduce operant learning ability.

A collection of Drosophila melanogaster mutants was created by insertion of a P-element into autosomes at a rate of one copy per genome. The abilities of 64 homozygous P-insertion mutants to produce a form of associative behavior were determined. Testing was based on an original paradigm of operant learning: interactions between Drosophila individuals when placed in a group situation in which the flies learned to inhibit their own activity to avoid punishment in the form of conflict with other individuals. Four lines were found in which, like the known learning mutants dunce and rutabaga, individuals did not show changes in their initial responses to each other. These lines were also studied using other paradigms of associative learning.

[Genetic aspects of learning mechanisms]. / Geneticheskie aspekty mekhanizmov obucheniia.

The following literature data point to the direct involvement of genome into processes related to learning; the protein and RNA synthesis intensification and the induction of the immediate-early genes expression in the course of learning, dependence of the memory consolidation upon the protein synthesis. In addition to the memory forms requiring induction of the gene expression for consolidation, there are forms of the long-lasting memory independent on the protein synthesis. The usage of genetic techniques in studying the mechanisms of learning and memory is considered.

[Autosomal mutations in drosophila interfering in the capacity for operant learning]. / Autosomnye mutatsii u drozofily, narushaiushchie sposobnost' k operantnomu obucheniiu.

Collection of autosomal P-insertional mutant stocks with single P-element per genome was created in Drosophila melanogaster. The learning ability was tested in 64 homozygous P-inserts using the original paradigm of self-starting operant learning in a group situation. Normal flies placed in a group situation learned to suppress their activity to avoid punishment. The learning-deficient mutants failed to change adaptively their initial locomotor response to presence of other individuals. The ability to learn in other paradigms of the associative learning is now being investigated in these mutant stocks.