Characteristics of the intraspecies interaction of rats with differing zoosocial experience

It has been found that among white outbred rats with different experience of intraspecies contact four types of reaction to the partner are singled out in the "stranger-resident" test: active, neutral passive, highly-aggressive. Belonging to one or another type is determined by the level and correlation of aggression and intraspecies sociability. Among animals isolated in an adult age, all four types of reaction to the partner are represented while in rats kept in isolation since 13--14th day of life only one type is presented--the active one. For animals of the control group the first three types of reaction are typical. It is revealed that only "late" isolation leads to a pathological increase of aggressivity in a part of the animals; an increase of aggression in "early" isolants may be considered as a consequence of sharp rise of intraspecies sociability. Conclusion is made about principal difference in mechanisms of aggression increase in "early" and "late" isolants.     

Behavioral reactions to stimulation of the emotiogenic zones of the brain in the rats with different individual experience

Emotional reactions evoked by electric stimulation of the hypothalamus and amygdala were studied in white outbred rats, grown either in conditions of isolation or in community. The method of self-stimulation in shuttle box was used. The values of self-stimulation reaction were significantly lower and those of avoidance reactions were higher in animals bred in isolation. Their food-procuring behaviour disappeared faster at stimulation of the negative emotiogenic zones. The observed differences are due to plastic reorganization of the brain reinforcing systems.     

Effect of the melanostatin analogue alaptide on dopamine-dependent behavior in rats reared in isolation

The effects of alaptide, a new analog of melanostatine, on self-stimulation of the lateral hypothalamus, rotation behavior in rotometer, and stereotypy were studied in rats bred in social isolation from other animals beginning from the 17th day of birth and rats bred in groups. Alaptide potentiated amphetamine-stimulated behavior only in rats reared in social isolation. This effect was lateralized: the left rotation dominated. In rats reared in isolation and in groups the effects of alaptide on self-stimulation were oppositely directed: in the former it increased and in the latter decreased the rate of self-stimulations with oppositely directed changes in pedal pressing duration. At the same time, alaptide suppressed the effects of amphetamine on self-stimulation of rats reared in isolation. The central dopamine mechanisms of melanostatine action are discussed.     

"Sensitive periods" in the systemogenesis of intraspecific aggression in rats

As a result of experiments conducted on male outbred white rats, approximate limits were established of two sensitive periods for the formation of intraspecies aggression of rats under the influence of contacts with the animals of the same age: sensitive period from 12th to 21st postnatal day for changing from playing behaviour into the aggressive one; and 40-60 days for differentiation of the aggressivity against the males and females. It was shown, that despite considerable change in the spectrum of aggressive reactions of early isolated rats towards intruders and low effect of these reactions, judging by response behaviour of intruders, these reactions were based on the emotionally-motivational state, typical for the formed aggressive behaviour. It was also found, that disturbances of the aggression formation in rats isolated in early age, were caused by deprivation of contacts with rats of the same age and not by general informational impoverishment of the environment where rat pups were bred.     

Effects of intra-amygdaloid TRH injections on motor activity and dominant-submissive behavior in rats competing for water.

The effect of thyrotropin releasing hormone (TRH) microinjections into the central amygdala (10 g in 0.5 1 into each side) on locomotor activity water intake and dominance behavior in a water competition test was investigated in male Wistar rats. TRH increased the general motility without altering the number of rearings. Intra-amygdaloid TRH injection to submissive rats resulted in a loss of subordinate position in these animals in the water competition test. A tendency to decrease dominance followed the injection of the peptide to the dominant animals. The effect of TRH in the dominance test does not appear to involve influence on the thirst drive as microinjection of the peptide did not change significantly the water consumption in thirsty rats.     

Increase in litter size and decrease of post-implantation loss of fetuses observed in an SPF colony of Wistar-Imamichi rats

The number of delivered offspring, corpora lutea and implantation sites was observed in an SPF colony of Wistar-Imamichi rats bred in a barrier system free of specified microorganisms and parasites and was compared with that of rats bred under conventional conditions. The litter size of 6142 SPF rats ranged from 1 to 20, averaging 12.4 +/- 0.04, a value significantly higher (P less than 0.001) than that of conventionally bred rats (11.0 +/- 0.04). Although the number of corpora lutea was also higher in SPF rats than under conventional conditions, the number of post-implantation losses in SPF rats with less than 10 offspring showed a marked decrease compared with conventionally bred rats. These results show that the number of delivered offspring is higher in SPF rats than in conventionally bred rats and indicate that the increase in litter size is due to the increase in the number of corpora lutea and decrease in post-implantation loss of embryos of fetuses.     

Time-dependent enhancement of lymphocyte activation by mitogens after exposure to isolation or water scheduling

The effects of isolation and water scheduling on mitogen induced lymphocyte proliferation were investigated. Isolated rats were animals which had been raised in group-housed conditions and then transferred to individual cages with ad lib access to water for a 1 or 2 week period. Water scheduled rats were maintained in group housing (5 rats per cage) with ad lib access to food but with access to water for a single 30 minute session each day. Responses of these groups were compared to those of animals which had been continuously group-housed with ad lib access to food and water. No differences in lymphocyte responses to phytohemagglutinin (PHA) were found 1 week after exposure to isolation. However, after 2 weeks, splenic and blood T lymphocytes from isolated animals demonstrated an increased proliferative response to suboptimum and maximum concentrations of PHA. Splenic B lymphocyte responses to lipopolysaccharide (LPS) from isolated animals were also increased by 2- to 3-fold compared to group-housed controls. Two weeks of exposure of animals to daily water scheduling similarly increased the splenic lymphocyte proliferation. This increased responsiveness to PHA was not accompanied by a significant change in the sensitivity of the lymphocytes to PHA, in the total number of white blood cells, or the proportion of splenic T or T helper lymphocytes. Our results show that the increase in lymphocyte proliferation is time-dependent, requires greater than 1 week of exposure to isolation and is due to factors other than changes in sensitivity to mitogen or T lymphocyte number.     

The role of the frontal cortex of the left and right hemispheres in regulating the intraspecific interaction of rats with differing zoosocial experience

By means of the analysis of probabilistic ethological structures of the intraspecies rats behaviour in the test "stranger-resident" and by the method of isolated destruction of the frontal cortex or the left and right hemispheres,--it is established that the frontal cortex of the left hemisphere regulates the intraspecies sociability and keeps it on a certain level, because the change (increase) of the intraspecies sociability is observed only at the unilateral destruction of the left frontal cortex. Isolation from the relatives in early ontogenesis leads to the loss of regulating influence of the left frontal cortex on the intraspecies sociability. In isolated animals the frontal cortex of the left hemisphere regulates the level and probability of the appearance of aggression. The right hemisphere ensures the adequate inclusion of the aggression in the probabilistic ethological structure of the total intraspecies behaviour; at its damage the forms appear of an adequate pathological aggression, and connection is lost between the elements of aggressive behaviour and the acts of intraspecies sociability.     

Changes in predatory and intraspecific aggressiveness of the male rat during food deprivation

A significant intensification of intraspecies aggression of mice-killing male rats was manifest under the influence of food deprivation, judging by two aggressive reactions of rats-residents towards intruders and by the number of rats performing such reactions. In conditions of free access to food, the mice-killing and not mice-killing rats did not differ by their intraspecies aggression.     

Rat behavior in a light/dark chamber: place preference task

After a 6-week social isolation (from 22nd to 70th day from birth) male Wistar rats (a sibship, 10 animals), were tested for 20 min in a light/dark box in order to reveal behavioral features of choice of their spatial localization in unknown conditions. Socially deprived rats significantly differed from control animals in longer time of the room choice, higher number of entries of the light section, and higher number of rearings, which was probably explained by their higher anxiety and lack of experience to estimate unexpected stimuli and select a response. The mean level of behavioral activity during exploration of the box defined by the number of elementary operations per minute remained constant and was significantly higher in the socially deprived rats than in the control animals.     

Comparative phylogeographic patterns of several vertebrates in the east Palearctic

An overview of our own and literature molecular phylogenetic studies on intraspecies variability in widely distributed Asian fishes, amphibians, birds, and mammals is presented. In many cases, the populations from the southeastern parts of the species ranges demonstrate distinct sets of haplotypes and increased variability. This means that such populations might have experienced isolation in refuges and that eastern Asia might have served as a hotspot in the speciation process for many Asian animals.     

Influence of partial intraspecies deprivation on short-term image-driven memory in rats

Behavior and short-term memory function were studied in adult rats risen under conditions of partial intraspecies social deprivation. Testing of delayed responses (and emotional state) showed that the partial deprivation of intraspecies communication at the early stage of postnatal ontogeny led not only to disorders of short-term memory in the adult rats, but also to behavioral alterations, which may be due to impaired development of the regulatory mechanisms of motivation and emotions.     

Environmental lighting and muricidal behaviour in the male Wistar rat.

Effects of different conditions of environmental lighting on the appearance of the muricidal behaviour in male Wistar rats have been studied. The animals were kept under different conditions of environmental lighting: 1) natural day light alternated with the dark of the night; 2) sodium, continuous light emitted by a sodium steam lamp; 3) neon, continuous light emitted by fluorescent neon tubes. The continuous sodium steam light increased the percentage of animals becoming muricide when compared to animals bred in a natural environment with a normal succession of day-night lighting. On the contrary, this percentage decreased if the rats of the same group are exposed to continuous light emitted by fluorescent neon tubes. As the exposure of rats to an environment under continuous light causes a reduction of the cerebral content of serotonin, the muricidal behaviour provoked in naturally non-muricide rats by this type of lighting could be related to this depletion.     

24-hour rhythms of splenic mitogenic responses, lymphocyte subset populations and interferon γ release after calorie restriction or social isolation of rats

To assess the effect of calorie restriction equivalent to a 66% food restriction or social isolation on splenic immune responses, calorie-restricted five week-old male Wistar rats, pair fed controls individually caged and pair fed controls caged in groups, were studied for four weeks. Calorie restricted and isolated rats showed increased splenic concanavalin A response with peak activity during the activity span. Mean 24 h values of splenic lipopolysaccharide response decreased in isolated rats compared to grouped rats. The highest values of T cells occurred in calorie restricted rats and those of B cells in isolated rats. Mean values of splenic CD4⁺ and CD8⁺ cells augmented in isolated or calorie restricted groups. The highest in vitro interferon-γ production occurred in the isolated group and the lowest in the grouped rats, the differences among groups being significant. Both experimental procedures generally disrupted 24-h rhythmicity of splenic immune parameters. Mean values of plasma corticosterone were higher in calorie restricted rats than in isolated rats and both differed significantly from grouped rats. The results indicate that either calorie restriction or social isolation augmented cell-mediated immunity in rat spleen.     

Behavioral and energetic costs of group membership in a coral reef fish

Animals in social aggregations often spend more time foraging than solitary conspecifics. This may be a product of the relative safety afforded by aggregations: group members can devote more time to foraging and less time to antipredator behaviors than solitary animals (the “risk reduction” effect). All else being equal, risk reduction should result in higher food intake for grouped animals. However, intragroup competition may force group members to spend more time foraging in order to obtain the same food ration as solitary individuals (the “resource competition” effect). We compared these opposing explanations of foraging time allocation in a coral reef fish, bluehead wrasse (Thalassoma bifasciatum). Aggregations of juvenile bluehead wrasse experience safety-in-numbers, and preliminary observations suggested that juveniles in aggregations spent more time foraging for copepods in the water column than solitary juveniles. However, the risk reduction and resource competition hypotheses are indistinguishable on the basis of behavioral observations alone. Therefore, we collected behavioral, dietary, and growth data (using otolith growth rings) for bluehead wrasse at multiple reefs around a Caribbean island. Despite spending more time foraging in the water column, grouped fish did not capture more prey items and had slower growth rates than solitary fish. Thus, the increased foraging time of grouped fish appears to reflect resource competition, not risk reduction. This competition may limit the size and frequency of aggregations among juvenile bluehead wrasse, which have been shown to experience reduced mortality rates in larger groups. Bluehead wrasse recruits also spent less time foraging but grew faster at sites where planktonic copepod prey were more abundant. This suggests the possibility that large-scale spatiotemporal variability in the abundance of planktonic copepods over coral reefs may produce corresponding variability in the dynamics of reef fish populations. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Time lags and global stability in two-species competition

Global asymptotic stability and equilibrium coexistence is established in two species Lotka-Volterra-type competition when there are time delays in interspecific interaction terms and the intraspecies competition is stronger than the interspecies competition.     

Protein synthesis in the critical periods of early postnatal ontogeny: its role in the development of the interspecific aggressive behavior of rats

Chronic administration of cycloheximide to young rats from 15-th to 30-th postnatal day before daily 3-hour seances of their contacts, disturbed the formation of animals intraspecies aggressivity. In adults it was manifested by hyperaggressivity and by changes of proportions of different reactions in the integral act of aggressive behaviour. By their character these disturbances were close to those observed in the young rats completely deprived of social contacts in this period of ontogenesis.     

Determination of taxonomic resolution capacity of conventional one-dimensional SDS-polyacrylamide gel electrophoresis of whole-cell proteins using Enterobacteriaceae

The capacity of one-dimensional SDS-PAGE of whole bacterial cells to both separate and cluster taxonomic units is studied using members of Enterobacteriaceae as test material. The results show that intraspecies variation can be detected and on the other hand the degree of taxonomic divergence which still can be grouped together is determined. In addition the system has high tolerance to changes in cell culture conditions making the usage of SDS-PAGE suitable for applications where rapid and reliable bacterial identification is needed.     

Long-lasting effects of social stress on peritoneal inflammation in some strains of mice

Adult male mice were kept for one week either one or four animals per cage. Some were maintained under the same social conditions for an additional 9 days (controls); their counterparts were either grouped (4 per cage) or isolated (1 per cage). Changes in housing conditions caused a significant increase of plasma corticosterone measured 30 minutes after separation or grouping of SWISS, C57C3H, and BALB/c but not of C57BL/6 mice. Peritoneal inflammation was induced by i.p. zymosan injection on day 9 after changes in housing conditions when corticosterone was again at its initial level in each group. Peritonitis-connected pain symptoms, exudatory PMN numbers, and cytokine (IL-1beta and MPC-1) and corticosterone levels were compared between animals living in stable social conditions with those shifted 9 days earlier from separation to the group or vice versa. These factors were unaffected by social stress in C57BL/6 mice and in SWISS animals transferred from the group to isolation. In all other instances at least two parameters were significantly different in the post-stressed and control animals, being either enhanced or inhibited. In conclusion, social stress had long-term consequences on the course of inflammation in three out of four investigated strains of mice.     

No effect of isolation on blood pressure and daily electrolyte excretion in rats

The effects of isolation stress on mean blood pressure (BP) and on body weight, water and food intake as well as on urine flow, urinary sodium and potassium excretion were studied in CFY and Long Evans rats. During a 7 day isolation period, food and water intake as well as urine flow, urinary sodium and potassium excretion, as expressed for 100 g body weight, were not changed in either group. Body weight increased similarly in isolated (38 +/- 2 g) and aggregated (41 +/- 5 g) CFY rats. Compared to group housed rats, BP in male CFY animals was not increased after a 7 day isolation (111 +/- 3 vs 111 +/- 3 mmHg, NS). In additional experiments high sodium intake by physiological saline drinking slightly elevated blood pressure but failed to induce arterial hypertension in isolated rats (118 +/- 2 vs 121 +/- 3 mmHg, NS). We conclude that, contrary to some reports from other laboratories, isolation stress has no detectable effect on BP and/or water and electrolyte balance.