RatDEGdb: a knowledge base of differentially expressed genes in the rat as a model object in biomedical research.

The animal models used in biomedical research cover virtually every human disease. RatDEGdb, a knowledge base of the differentially expressed genes (DEGs) of the rat as a model object in biomedical research is a collection of published data on gene expression in rat strains simulating arterial hypertension, age-related diseases, psychopathological conditions and other human afflictions. The current release contains information on 25,101 DEGs representing 14,320 unique rat genes that change transcription levels in 21 tissues of 10 genetic rat strains used as models of 11 human diseases based on 45 original scientific papers. RatDEGdb is novel in that, unlike any other biomedical database, it offers the manually curated annotations of DEGs in model rats with the use of independent clinical data on equal changes in the expression of homologous genes revealed in people with pathologies. The rat DEGs put in RatDEGdb were annotated with equal changes in the expression of their human homologs in affected people. In its current release, RatDEGdb contains 94,873 such annotations for 321 human genes in 836 diseases based on 959 original scientific papers found in the current PubMed. RatDEGdb may be interesting first of all to human geneticists, molecular biologists, clinical physicians, genetic advisors as well as experts in biopharmaceutics, bioinformatics and personalized genomics. RatDEGdb is publicly available at https://www.sysbio.ru/RatDEGdb.

Differential expression of 10 genes in the hypothalamus of two generations of rats selected for a reaction to humans.

Individual behavioral differences are due to an interaction of the genotype and the environment. Phenotypic manifestation of aggressive behavior depends on the coordinated expression of gene ensembles. Nonetheless, the identification of these genes and of combinations of their mutual influence on expression remains a difficult task. Using animal models of aggressive behavior (gray rats that were selected for a reaction to humans; tame and aggressive rat strains), we evaluated the expression of 10 genes potentially associated with aggressiveness according to the literature: Cacna1b, Cacna2d3, Drd2, Egr1, Gad2, Gria2, Mapk1, Nos1, Pomc, and Syn1. To identify the genes most important for the manifestation of aggressiveness, we analyzed the expression of these genes in two generations of rats: 88th and 90th. Assessment of gene expression levels was carried out by real-time PCR in the hypothalamus of tame and aggressive rats. This analysis confirmed that 4 out of the 10 genes differ in expression levels between aggressive rats and tame rats in both generations. Specifically, it was shown that the expression of the Cacna1b, Drd2, Egr1, and Gad2 genes does not differ between the two generations (88th vs 90th) within each strain, but significantly differs between the strains: in the tame rats of both generations, the expression levels of these genes are significantly lower as compared to those in the aggressive rats. Therefore, these genes hold promise for further studies on behavioral characteristics. Thus, we confirmed polygenic causes of phenotypic manifestation of aggressive reactions.

Adolescent oxytocin treatment affects resident behavior in aggressive but not tame adult rats.

There are indications that exposing adolescent rodents to oxytocin (OT) promotes social activity and reduces anxiety in adulthood. Adult male gray rats selected for elimination and enhancement of the aggressive response to humans, when exposed to OT, showed divergent changes in the resident behavior towards the intruder. It could be assumed that adolescent administration of both OT and antagonist of OT receptor (OTR) would also have different long-term effects on resident behavior and startle reflex in adult aggressive and tame rats. The aim of this work is to study the long-term effects of adolescent administration of both OT and antagonist of OT receptor (OTR) on resident behavior and startle reflex in adult tame and aggressive male gray rats. Starting at the age of 28 days, the animals received nasal applications of 5 µL of oxytocin solution (1 µg / µL) or saline for 5 days (daily). At the age of two months, the acoustic startle amplitude was assessed in two series of 5 acoustic stimuli. The resident-intruder test was performed one week later. Antagonist of OT receptor l-368,899 was administered intraperitoneally (i.p.) once at a dose of 5 mg/kg at the age of 30-33 days. Subsequent startle reflex tests were performed 20 days later, at the age of 50-53 days. A week later, the resident-intruder test was performed on the same rats. The startle amplitude in aggressive rats of the control group (in two series of acoustic stimuli) and those having received saline (in the first series) was larger than in the corresponding tame groups. Oxytocin and saline solutions did not significantly affect the startle amplitude compared to control animals. After saline administration, the attack latency in tame rats was longer than in aggressive rats (P <0.05). Oxytocin treatment caused a prolongation of this period in aggressive males compared with control animals receiving saline solution (P <0.01). In addition, oxytocin administration in aggressive males caused an increase in the time of social behavior, which did not include aggressive and same-sex behavior, as compared with the corresponding control animals (P <0.05). Exogenous oxytocin receptor antagonist (l-368,899) did not affect the startle amplitude and behavior in the resident-intruder test in aggressive and tame male rats. Adolescent OT treatment causes a prolongation of both the attack latency and social behavior in the resident-intruder test in adult aggressive male rats, but does not affect these parameters in tame rats.

Modeling of Focal Seizures with Automatisms in Rats with Pendulum Movements.

Phenotypical study was carried out in rats with pendulum movements. The animals exhibited a high level of abortive seizures in response to audiogenic stimuli and longer postictal catalepsy in comparison with those in Wistar population. Seizure severity positively correlated with the duration of poststimulus catalepsy (r=0.90). High aggressiveness towards humans, the absence of BP elevation in stress, lower body weights, and lower weights of the kidneys and spleen in PM rats are considered concomitant traits. Correlations were detected between startle-1 and BP in rats with pendulum movements (r=0.70) and between startle-10 and BP in narcotized Wistar rats (r=-0.0.71). The newly described signs in rats with pendulum movements did not contradict the signs of the focal seizure model with typical automatisms in humans.

[Expression of apoptosis genes in the brain of rats with genetically defined fear-induced aggression].

The programmed cell death (or apoptosis) plays an important role both in developing and mature brains. Multiple data indicate the involvement of processes of apoptosis in mechanisms of different psychopathologies. At the same time, nothing is known about the role of apoptosis in the regulation of genetically defined aggression. In the present work, the expression of the genes that encode main pro- and antiapoptotic BAX and BCL-XL proteins, as well as caspase 3 (the main effector of apoptosis), in different brain structures of rats that were selected on a high aggression towards human (or its absence) was studied. A significant increase in the expression of the gene encoding caspase 3 was detected in the hypothalamus. This was accompanied by a significant decrease in the expression of proapoptotic Bax gene in the hippocampus and increase in mRNA level of antiapoptotic Bcl-xl gene in the raphe nuclei area of midbrain in highly aggressive rats. An increase in the ratio Bcl-xl: Bax was found in the midbrain and amygdala; a trend towards an increase in the ratio was also found in hippocampus of aggressive animals compared to tame animals. Thus, we demonstrated that genetically defined fear-induced aggression is associated with significant changes in the genetic control of apoptosis in the brain. It is assumed that an increase in the Bcl-xl gene expression (accompanied by a decrease in the Bax gene expression) can indicate an increase in the threshold of neuronal apoptosis in highly aggressive rats.

[Comparative Analysis of Behavior in The Open-field Test in Wild Grey Rats (Rattus norvegicus) and in Grey Rats Subjected to Prolonged Selection for Tame And Aggressive Behavior].

The aim of this work is analysis of the open-field behavior in grey rats selected for the tame and aggressive behavior in comparison with the wild grey rats. Significant influences of the rat group factor on the 13 of 19 behavioral features studied in the open-field were found. This effect, in general, depends on existence of great differences between behaviors of the wild rats from the one hand and behaviors of the tame and aggressive rats from the other. The behaviors of the rats from the last two groups are practically identical. Multidimensional analysis confirms the distinct separation in coordinates of the two main components of the wild rat behavior from the behavior of both the tame and selectively bred aggressive rats. The first main component dimension corresponds to the grade of fear, which was significantly enhanced in the wild rats. So, in spite of the equality of behavioral aggressiveness of the wild rats and the rats selected for aggression with the glove test, the behavior of selected aggressive rats in the open-field is analogous to behavior of the rats selected for tameness. Comparison of behavioral features with the hormonal stress responsiveness allowed us to conclude that the aggressive behavior of the wild and se lected for aggression rats based on different motivational and neuroendocrine processes.

The influence of social environment in early life on the behavior, stress response, and reproductive system of adult male Norway rats selected for different attitudes to humans.

The influence of social disturbance in early life on behavior, response of blood corticosterone level to restraint stress, and endocrine and morphometric indices of the testes was studied in 2-month Norway rat males from three populations: not selected for behavior (unselected), selected for against aggression to humans (tame), and selected for increased aggression to humans (aggressive). The experimental social disturbance included early weaning, daily replacement of cagemates from days 19 to 25, and subsequent housing in twos till the age of 2months. The social disturbance increased the latent period of aggressive behavior in the social interaction test in unselected males and reduced relative testis weights in comparison to the corresponding control groups. In addition, experimental unselected rats had smaller diameters of seminiferous tubules and lower blood testosterone levels. In the experimental group, tame rats had lower basal corticosterone levels, and aggressive animals had lower hormone levels after restraint stress in comparison to the control. The results suggest that the selection in two directions for attitude to humans modifies the response of male rats to social disturbance in early life. In this regard, the selected rat populations may be viewed as a model for investigation of (1) neuroendocrinal mechanisms responsible for the manifestation of aggression and (2) interaction of the hypothalamic-pituitary-adrenal and hypothalamic-pituitary-gonadal systems in stress.

Functional characteristics of serotonin 5-HT2A and 5-HT2C receptors in the brain and the expression of the 5-HT2A and 5-HT2C receptor genes in aggressive and non-aggressive rats.

The functional activity of serotonin 5-HT(2A) and 5-HT(2C) receptors and the expression of the genes encoding them were studied in Norway rats bred for 60 generations for the presence and absence of high levels of stress-evoked aggression to humans. There were no significant differences in the levels of 5-HT(2A) receptor mRNA in the midbrain, frontal cortex, and hippocampus and the extents of head twitching evoked by the 5-HT(2A) agonist DOI in rats with and without genetically determined high levels of aggression. Administration of the selective 5-HT(2C) agonist MK-212 weakened reflex startle in response to an acoustic signal (the acoustic startle response) in non-aggressive animals but had no significant effects on the response in aggressive animals. Increases in the level of 5-HT(2C) receptor mRNA were seen in the frontal cortex and hippocampus in non-aggressive rats as compared with aggressive animals. Increases in the expression of the 5-HT(2C) receptor gene and the functional state of 5-HT(2C) receptors were seen in the brains of non-aggressive rats, without any changes in the 5-HT(2A) receptor mRNA level or receptor sensitivity; this is evidence for the involvement of 5-HT(2C) receptors in the mechanisms inhibiting fear-evoked aggressive behavior.