Effect of Silicon Dioxide Nanoparticles on Syrian Hamsters Infected by Opisthorchis felineus: 1H MRS Study of the Brain

In recent years, silicon dioxide nanoparticles have been widely used in medicine and the pharmaceutical industry, however, their effect on the brain has hardly been studied. We assessed the effects of long-term consumption of 5-nm amorphous silicon dioxide nanoparticles (SiO₂-NPs) by Syrian hamsters infected with the trematodes Opisthorchis felineus on the hippocampus and frontal cortex. Spectroscopic determination of brain neurometabolites, performed using a horizontal Magnetic Resonance Imaging system at 11.7 Tesla magnetic field, has shown that the ratio of the excitatory neurotransmitters (glutamate + glutamine + aspartate) to the inhibitory ones (GABA + glycine) was higher in the animals infected with O. felineus. However, pre-consumption of the SiO₂-NPs solution prevented this imbalance. In addition, the protective effect of SiO₂-NPs on the level of myo-inositol and glycine was found. It is concluded that the use of SiO₂-NPs can neutralize the negative effects of infectious factors on the brain.

Studyng the effects of Cantharellus cibarius fungi on Opisthorchis felineus trematode and on parasite host - C57BL/6 inbred mice

Opisthorchiasis is a dangerous parasitic disease caused by trematodes in the family Opisthorchiidae. One of the causes of this infection is the species Opisthorchis felineus, which is common in the Russian Federation and Western Europe. The disease has a large number of complications and relatively few effective treatments, so nowadays it is relevant to look for new drugs for the treatment of opisthorchiasis, with the maximum antiparasitic and minimal side effect. In this work, a potentially anthelmintic effect of the methanol extract of the golden chanterelle mushroom (Cantharellus cibarius) was investigated. In in vitro experiments, the significantly reduced mobility and survival rates of juvenile O. felineus specimens with increasing concentrations (10-1000 pg/ml) of the C. cibarius extract were shown. In in vivo studies, administration of the C. cibarius extract on the first day after parasitic infection of inbred C57BL/6 mice resulted in a decrease of the number of helminths in the bile ducts of the liver, evaluated 6 weeks after infection. In another series of experiments, administration of the C. cibarius extract for 7 days to mice infected with O. felineus for five weeks had no anthelmintic effect. In both cases, the state of the infected hosts, evaluated by a number of physiological and biochemical parameters (relative weight of organs, blood indices), did not deteriorate, indicating that there was no adverse effect of the C. cibarius extract. The results obtained suggest that the C. cibarius extract might have anthelmintic properties if applied as parasite larvae excyst.

Physicochemical Properties and Anti-Opisthorchosis Effect of Mechanochemically Synthesized Solid Compositions of Praziquantel with Glycyrrhizic Acid Disodium Salt

The mechanochemical preparation of solid compositions of praziquantel with plant saponin (glycyrrhizic acid disodium salt) is described. The study of a number of physicochemical parameters showed that dissolving solid compositions in water is accompanied by the inclusion of praziquantel molecules into micelles, which are formed in the solution of the glycyrrhizic acid disodium salt. Using the opisthorchiasis model caused by Opisthorchis felineus, we found a 4- to 11-fold increase in the anthelmintic activity of praziquantel in the composition as compared to the official praziquantel. According to the pharmacokinetic data, the use of the composition increased the bioavailability of praziquantel 3 times.

[Resistance of DBA/2J Mice to the Chronic Social Defeat Stress]

We investigated behavioral changes in male mice DBA/2J after the acquisition of a long experience of social defeats in agonistic interactions with aggressive partners of C57BL/6J and DBA/2J lines. The long experience of social defeat in DBA/2J mice did not change the strategy of theirbehavi6r during agonistic interactions. Reduced communicativeness and increased level of anxiety were found in the "partition" and "elevated plus maze" tests. There were no changes in locomotor activity in the "open field" test. After 20-30 days of social defeat stress there were no signs of depression, determined by the behavior during confrontations and in the Porsolt test. There was no sign of catalepsy, decreased exploratory be- havior and impaired social recognition. Thus, the mice of this strain can be considered relatively resis- tant to the development of depressive-like state under chronic social stress and may be used for the study of the mechanisms of such stability.

[Effects of buspirone complex with glycyrrhizic acid on behavior of mice with anxious-depressive state]

We report here studies of the effects of subchronic administration of 5-HT1A receptor agonist buspirone and its novel complex with glycyrrhizic acid (GA) to C57BL/6J mice at the different stages of the anxious-depressive state formation, induced by conditions of social stress. The experiment of agents' administration during the conditions of stress (beginning with initial stage) showed that only complex had a protective effect revealed in prevention of the anxiety with the high level of mice communicativeness maintenance. At the stage when the anxious-depressive state is completely formed, buspirone and its complex with GA decreased mice motor activity however complex--less significantly. Here we discuss a possible mechanism of action of investigated agents on the background of changes in the sensitivity of 5-HT1A receptors, induced by the formation of the anxious-depressive state of mice with experience of social stress. Despite of different effects of agents depending on the stage of the anxious-depressive state development, novel buspirone complex with GA has some advantage over buspirone.

[Development of movement disorders in DBA/2J male mice under repeated experience of aggression]

Changes in the behavior of DBA/2J mice after gaining repeated experience of aggression have been investigated. It was shown that the long-term experience of aggression led to development of hyperactivity estimated as increased motor activity in different tests: open field, elevated plus maze and during testing of reaction to a novelty. Symptoms of attention deficit estimated in the "partition" test as a reduction of the communicativeness and the lack of reaction to unfamiliar partner were noticed. Appearance of a large number of hyperkinesis manifested most often in the form of sudden involuntary head movements (jerks) was observed in the behavior of aggressive males during agonistic interactions. Most of the changes in the behavior of DBA/2J mice differed significantly from previously detected in the behavior of aggressive mice of C57BL/6J and CBA/Lac strains, suggesting a significant contribution of heredity that determines the features of behavioral disorders that occur under the influence of long-term experience of aggression. Similarity of symptomatics of movement disturbances in mice and in humans with some neurological diseases is discussed.

[Effects of buspirone on the behavior of female mice in a model of social discomfort]

The influence of acute and chronic (14 days) buspirone administration (1 mg/kg, intraperitoneally) on the behavior of C57BL/6J female mice, being in social discomfort, were studied. The conditions of social discomfort include the permanent habitation of females in the cage with aggressive males through a perforated partition and daily presence during intermale confrontations. The dynamic changes of 5-HT1A-receptor sensitivity in the brain of female mice, estimated by the female behavior after 30 min ofbuspirone administration, were discovered. The sensitivity increased at the early stages of pathological behavior development (10 days) and decreased after 20-30 days. Females who had reduced of 5-HT1A receptor sensitivity after 30 day of maintenance in social discomfort conditions also showed a decreased sensitivity on chronic buspirone administration.

[Effects of chronic buspirone treatment on female mice exposed to the long-lasting psychoemotional influence]

The effects of chronic treatment (30 days) with the 5-HT1A receptor partial agonist buspirone (0.05, 1 and 10 mg/kg i.p.) on the behaviour of C57BL/6J female mice exposed to long-lasting psychoemotional influence were studied. The influence involved forced living of each female with an aggressive male separated with a perforated transparent partition in the same cage and daily female's presence during 10-min intermale confrontations behind a partition caused by introducing of another male to the aggressive male. Chronic buspirone injection (in all used doses) did not affect the behaviour of females estimated in the "partitions" and "open field" tests at the end of the drug treatment. The anxiolytic effect of buspirone only at the dose of 1 mg/kg on the female's plus-maze behaviour was revealed. In the Porsolt, test buspirone in the dose of 1 mg/kg caused a slight increase in the duration of immobility indicating a slight pro-depressive effect. Thus, chronic buspirone treatment of females exposed to the long-lasting psychoemotional impact has a different effect on their behaviour depending on the dose and test conditions.

[3H]SCH 23390 binding in various brain regions of C57BL/6J mice with repeated experience of victory or social defeat in agonistic interactions

The binding of [3H]SCH 23390 has been studied in various brain regions of male mice with the experience of repeated victory (winners) or defeat (losers) gained over 10 (T10) and 20 (T20) days of daily agonistic confrontations. In the frontal cortex, B(max) of [3H]SCH 23390 binding sites was found to be increased in T10 losers and decreased in T20 losers when compared to the control mice. In the striatum, T10 and T20 winners had reduced values of [3H]SCH 23390 binding sites than the ones in the control mice. The K(d) was increased in the frontal cortex of T10 losers and T10 winners as well as in the amygdala of T20 losers. Reduced K(d) values were found in the striatum of all experimental groups as well as in the amygdala of T20 winners. Thus, both specific changes relating to social behavior patterns and non-specific ones in [3H]SCH 23390 binding were found in the brain regions of mice after 10 and 20 days of intermale confrontations.

[Mouse gender-related behavioral responses to long-lasting psychoemotional influence]

Behavior of male and female inbred mice of C57BL/6J strain was studied after long-lasting psychoemotional influence consisting of forced living with aggressive male separated with a perforated transparent partition in the same cage, and daily presence of males and female during 10-min intermale confrontations behind a partition caused by introducing intact mouse to an aggressive male. In a month, the increased level of anxiety in mice of both genders was revealed in the elevated plus-maze test. However, only females showed a longer time of passive swimming in the Porsolt's test. Under these conditions, females demonstrated some decrease of communication in the partition test. Accordingly, a more expressed behavior response was revealed in females in comparison with males on long-lasting psychoemotional influence.

[Effects of ethanol on metastasis of Lewis lung carcinoma in male mice with different social states]

The aim of this work was to study the effect of ethanol on experimental metastasis of Lewis lung carcinoma in male mice in positive or negative emotional states. Sensory contact model was used for generating animals with repeated experience of social victories or defeats. Tumor cells were injected into the tail vein after 20 days of agonistic interactions, and the number of metastases in the lung was calculated 16 days later. Group-housed mice were used as the controls. Mice of all experimental groups were chronically treated with ethanol (20%, 2 ml/kg of weight, i.p.) and saline during 7 days starting with the day of tumor cells injections. The experimental metastasis was shown to develop differently in mice with opposing social experience: saline-treated winners had significantly less metastases in the lung than the saline-treated losers. Chronic ethanol injections decreased the number of metastases in the losers, increased it in the winners and did not affect the controls. The results obtained indicate that effects if ethanol on Lewis lung carcinoma metastasis depend on psychoemotional status in male mice.

An experimental approach for the study of psychotropic drug effects under simulated clinical conditions

The sensory contact model can induce various different psychopathological states in male mice (anxious depression, catalepsy, social withdrawal, pathological aggression, cognition disturbances, anhedonia, alcoholism etc.). Additionally, this model facilitates the screening of drugs for therapeutic properties, preventive properties and efficiency under simulated clinical conditions. This approach can reveal the action of drugs at different stages of disease development. It is proposed that this pharmacological approach can be applied for the screening of various novel psychotropic drugs.

[Influence of experimental context on the development of anhedonia in male mice exposed to chronic social stress]

Consumption of 1% sucrose solution supplemented with 0.2% vanillin was studied in two experimental contexts in male mice living under chronic social stress induced by daily experience of defeats in agonistic interactions and leading to development of depression. In the first experiment, vanillin sucrose solution was made available as an option along with water during 10 days for mice living in group home cages. Then the mice were subjected to repeated social defeat stress and during exposure to stress they were provided with both vanillin sucrose solution and water using a free two-bottle choice paradigm. In the other experiment, vanillin sucrose solution was first offered to mice after 8 days of exposure to social defeat stress. Males familiar with vanillin sucrose solution showed vanillin sucrose preference while experiencing defeat stress: consumption of vanillin sucrose solution was about 70% of total liquid consumption. However, the consumption of vanillin sucrose solution per gram of body weight in mice exposed to social stress during 20 days was significantly lower than in control males. In the second experiment, males after 8 days of social defeat stress were found to consume significantly less vanillin sucrose solution as compared to control males. On average, during two weeks of measurements, vanillin sucrose solution intake was less than 20% of total liquid consumption in males. Consumption per gram of body weight also appeared to be significantly lower than in control group. The influence of experimental context on the development of anhedonia measured as a reduction of sucrose solution intake by chronically stressed male mice is discussed.

Effects of single episodes of severe stress on the behavior of male and female CBA/Lac and C57BL/6J mice

Experiments were performed to compare the behavior of male and female mice of the inbred strains CBA/Lac and C57BL/6J in the open field test after single episodes of severe stress imposed by forced swimming. Testing was performed 2 h (first test) and one day (second test) after stress. Control animals were intact males and females of these strains, and were also tested in the open field on two sequential days. Both male and female CBA/Lac mice showed increases in the latent period of excursions from the center of the field 2 h after stress. This change persisted to the second test in female CBA/Lac mice. In female C57BL/6J mice, there were changes in four of seven behavioral measures 2 h after stress, though at one day their behavior was as in control individuals. Stress had virtually no effect in males of this strain, only increasing the number of grooming acts in the first test. In addition, detailed analysis of the effects of repeat testing in control and stressed individuals of these mouse strains also revealed interstrain and gender-related differences in the effects of stress. The possible existence of increased basal (trait) and situational (state) anxiety in female C57BL/6J and CBA/Lac mice respectively is discussed.

[Effects of acute and chronic introduction of fluoxetine on anxiety-depressive condition of male and female mice]

The effects of acute and chronic fluoxetine treatment in intact and anxiety-depressive male and female inbred mice of the C57BL/6J strain were studied. The gender differences in the behaviour of mice in the tests estimating anxiety, locomotion and exploration activity, communication, and depressive-like state after fluoxetine injection were established. The dependence of fluoxetine treatment on normal or pathological state in mice was discovered. It was concluded that use of the animals in pathological condition and chronic (but nor acute) fluoxetine treatment are represented as the most correct estimative means of antidepressant efficiency.

[Effect of a single severe stress on behaviour of males and females in the mouse inbred strains CBA/Lac and C57BL/6J]

The effect of single severe stress in the form of forced swimming on the behavior of males and females in the mouse inbred strains CBA/Lac and C57BL/6J were examined in the open field test. Measurements were carried out within two hours after the stress exposure (Trial 1) and repeated 2 hours thereafter (Trial 2). Intact males and females of the both mouse strains which tested in the open field twice too were used as control. An increased latency was found until first escape from the center both in males and females of the CBA/Lac strain within two hours after the end of forced swimming. This parameter was still high in females in the Trial2. Four out of seven behavior parameters were changed in females of the C57BL/6J strain two hours after the stress exposure, but their behavior was similar to control in the Trial 2. The males of the C57BL/6J strain demonstrated the least changed behavior in the open field test after the stress exposure with the exception of increased number of grooming in the Trial 1. Further on, a detailed analysis of repeated testing in the open field within intact and stressed mice of both strains was performed. This comparison allowed revealing hereditary and gender peculiarities in the mouse behavior after single severe stress exposure. The results are discussed in respect to the possible genetically inherent increased traitanxiety in females of C57BL/6J strain and the state of anxiety in females of CBA/Lac strain.

Formation of behavioral pathology in female C57BL/6J mice exposed to prolonged negative psychoemotional conditions

Prolonged exposure of females to negative psychoemotional conditions by permanent keeping with aggressive males on the other side of a perforated partition in a cage with daily witnessing of intermale confrontations had negative influences on the behavior of females, assessed using a variety of ethological tests. The elevated maze test and the open field test provided evidence for the development of marked anxiety in the females, with inhibition of motor and investigative activity. Decreases in the responses of females close to the partition to familiar and unfamiliar males one month after the onset of exposure to negative psychoemotional conditions and before the end of the experiment provided evidence for a decrease in communicativeness. After two months of exposure to negative psychoemotional conditions, intermale confrontations also ceased to interest females, as shown by the partition test. The hotplate test revealed worsening of pain sensitivity in experimental females. More than half of the individuals demonstrated impairment to the cyclicity of sexual cycles with increases in the duration of diestrus. After being kept in negative psychoemotional conditions, females ceased to differentiate littermates by social status and gender, as shown by social/sexual recognition tests. All these data provide grounds for suggesting the development of an anxious-depressive state in females after being kept in negative psychoemotional conditions for prolonged periods.

[Development of anhedonia under negative experience of social confrontations in male mice]

Possible development of anhedonia in male mice under chronic stress produced by social confrontations was investigated. Cheese, instead of traditional sucrose solution, was used as a positive reinforcement. It has been shown that the controls, the winners with repeated experience of aggression accompanied by victories and the losers with repeated experience of social defeats, irrespective of their social status, preferred to eat cheese, but not pellets, under the free choice conditions--80% of total food. After three days of cheese deprivation, the least food motivation and the least level of cheese consumption were observed in the losers as compared with the controls and winners. Influence of social stress as well as negative psychoemotional state produced by social defeats, on development of anhedonia as a symptom of major depression, is discussed.

[Choice of "control" in experimental researches of animal social interactions in mice]

The purpose of the present experiment was to clarify the individuals as an appropriate "control" in research of social interactions in animals. As it has been established for the C57BL/6J mouse strain, the best control animals are individually housed for 5 days males in contrast to males placed with females or with other males in groups of 3-10 mice. Such male mice were less anxious and had high exploratory and motor activities in the elevated plus-maze, open-field, forced swimming and exploratory-activity tests.

A Model of Anxious Depression: Persistence of Behavioral Pathology

Chronic psychoemotional stress induced by negative experience of social defeats in intermale confrontations over a period of 30 days was found to lead to the development of anxious-depressive symptomatology in male mice. Cessation of the psychopathogenic conditions and placing of depressed animals in comfortable conditions for 1-2 weeks with females did not lift the pathological state. Individuals continued to show marked anxiety, a behavioral deficit, decreased communicativeness, and a high level of depressivity, as revealed by a variety of behavioral tests. Persistence of the resulting psychoemotional disturbance in these animals is evidence for the development and persistence of the behavioral pathology requiring drug treatment.

Anxiety in females induced by long-lasting psychoemotional influences

The experiments reported here addressed the behavior of female mice after long-lasting psychoemotional influences consisting of daily placing of females in the presence of intermale confrontations, the females being on the other side of a transparent perforated partition; females were subsequently placed in the territory (litter) in which the conflict had taken place. These conditions induced anxiety in the females, detected in the elevated cross maze test. In the absence of any marked prodepressant effect, females were more passive in the Porsolt test. There was also an increase in the time spent by females close to the partition both 5 min before the start of the conflict and during the intermale conflict.

[Development of pathological behavior in C57BL/6J female mice under the long-lasting psychoemotional influence]

Long-lasting psychoemotional influence consisting of permanent stay of females with aggressive males separated with a perforated transparent partition in the same cage, and daily presence of females during intermale confrontations, is negative toward the females' behavior estimated in the some ethological tests. Elevated plus-maze and open field tests reveal an increased anxiety and inhibited exploratory behavior and motor activity. Within a month, the decreased females' reactions near the partition to both familiar and unfamiliar males testify to decreased communicativeness. In two months from the beginning, intermale confrontations become uninteresting for females too, as it was shown in the partition test. Abnormalities in the pain sensitivity estimated in the hot-plate test are found in females after the psychoemotional influence. More than half of all females have a prolonged diestrous stage of the estrous cycle. Moreover, after the psychoemotional influence females lose the capability to recognize intact female and male littermates as well as aggressive and submissive males. Taken together the results suggest that long-lasting psychoemotional influence can cause the anxiety-depression states in females.

[The animal model of anxious depression: persistence of behavior pathology]

It has been shown that chronic psychoemotional stress caused by repeated experience of defeats in agonistic interactions during 30 days led to development of the anxiety depression--like state accompanied by pronounced anxiety, behavioral deficit, decreased communication, and increased depressiveness as estimated by various behavioral tests in male mice. This psychopathological state still existed after 1-2 weeks living with females in comfortable conditions (without confrontations with other males), that testified to persistence of behavior pathology.

[Dynamic changes of brain serotonergic and dopaminergic activities during development of anxious depression: experimental study]

Chronic psychoemotional stress of social defeats produces development of experimental anxious depression in male mice similar to this disorder in humans. 5-HT and 5-HIAA levels, TPH and MAO A activities, 5-HT1A-receptors in different brain areas were investigated at different stages of development of experimental disorder. It has been shown that initial stage (3 days of social stress) is accompanied by increase of 5-HT level in some brain areas. Decreased 5-HIAA levels in the hippocampus, amygdala and nucleus accumbens were discovered at the stage of forming depression (10 days of social stress). Pharmacological desensitisation and decreased number of 5-HT1A-receptors were shown in frontal cortex and amygdala. At the stage of pronounced depression (20 days of stress), there were no differences in 5-HT and 5-HIAA levels in all brain areas (excluding hypothalamus) of depressive animals. However increased number of 5-HT1A-receptors and decreased affinity in amygdala and decreased TPH and MAOA activities in hippocampus were found in depressive mice. Hypofunction of serotonergic system is suggested at the stage of pronounced depression state in animals. Similar processes had place in brain dopaminergic systems. It is concluded that dynamic changes of brain monoaminergic activities accompany the development of anxious depression in animals. Various parameters of monoaminergic systems are differently changed depending on brain area, mediator system and stage of disorder.

Effects of Repeated Experience of Aggression on the Aggressive Motivation and Development of Anxiety in Male Mice

The sensory contact model allowed aggressive behavior to be formed in male mice as a result of repeated experience of victory in daily social confrontations. In individuals of the low aggressivity, high emotionality line CBA/Lac, repeated experience of aggression led to the development of anxiety, assessed in the elevated cross maze test. Males showed increases in aggressive motivation, measured in terms of increases in behavioral reactions to conspecifics in the partition test. It is concluded that repeated experience of aggression provokes the development of anxiety in male mice and that the level of developing anxiety, like its behavioral correlates, depends on the duration of aggressive experience and the mouse line studied.

[Changes in the expression of monoaminergic genes under the influence of repeated experience of agonistic interactions: from behavior to gene]

The role of genetic and environmental factors as well as brain neurochemistry in regulating aggressive and submissive behaviors in animals are considered. We present a review of data on changes in brain monoaminergic activity (synthesis, catabolism, receptors) and on the expression of monoaminergetic genes under repeated daily agonistic confrontations in male mice. A repeated experience of aggression was shown to result in the total activation of the dopaminergic system and the inhibition of the serotonergic one. This was accompanied by a decrease in the mRNA level of the catechol-O-methyltransferase gene in the midbrain and an increase of the mRNA level of the dopamine transporter and tyrosine hydroxylase genes in the ventral tegmental area of aggressive male mice. Repeated experience of social defeats produced dynamic changes in the serotonergic system of some brain areas and an increase of the mRNA level of the serotonin transporter and monoamine oxidase A genes in the midbrain raphe nuclei. Theoretical and methodological possibilities of the proposed ethological approach for studying molecular mechanisms of agonistic behavior are discussed in the context of the fundamental problem of investigating the ways of regulation from behavior to gene.

[Long-term isolated housing causes anxiety in C57BL/6J female mice]

Behaviour of female C57BL/6J strain mice was studied in the elevated plus-maze and Porsolt's tests after either long-lasting individual housing or keeping with daily shifting group-housed females (social instability). After 2-3 months, an increased level of anxiety in the individually housed females was revealed in the elevated plus-maze. However, in 3 months the least passive behaviour in the Porsolt's was in the individually housed females. No changes were found in behaviour of females individually housed at 3 weeks of age for 4 months. Also, females with preliminary social contacts with males and following individual housing for one month had not any abnormalities in the used behavioural tests. Social instability conditions did not significantly influence the females' plus-maze behaviour, but decreased the passive behaviour in the Porsolt's test.

Ethological Analysis of the Effects of Fluoglyzine on Mice Exposed to Chronic Social Stress

Ethological study of a new agent fluoglyzine (fluoxetine analog) was carried out. Porsolt test revealed a positive antidepressant effect of fluoglyzine in mice with pronounced depression-like state. This effect was more pronounced than the effect of fluoxetine. Both drugs effectively improved communicative activity of experimental animals. Anxiety tests showed no anxiolytic effects of fluoglyzine and fluoxetine.

[Anxiety in females caused by long-term psycho-emotional stress]

Behaviour of female mice was studied under long-lasting psychoemotional influence. Daily presence of females during inter-male confrontations through a perforated transparent partition in the same cage and the next female placing on the male territory (sawdust) after the confrontations, were included as the influencing factors. Under these conditions, the increased level of anxiety in the females was revealed in the elevated plus-maze test. At the same time, the females demonstrated a more passive behaviour in the Porsol test. The psycho-emotional influence also affected the females' behaviour in the partition test. The females spent a significantly longer time near the partition both 5 minutes prior to and during the inter-male confrontations.

[Effects of repeated experience of aggression on aggressive motivation and development of anxiety in male mice]

The sensory contact technique allows an aggressive type of behavior to be formed as a result of repeated experience of social victories in daily agonistic confrontations. In mice of the low-aggressive and high-emotional CBA/Lac strain repeated positive fighting experience increases plus-maze anxiety. Behavioral reactivity of males to other conspecifics in the partition test (which measures aggressive motivation) significantly rises. It is concluded that repeated experience of aggression provokes the development of anxiety in male mice. The results suggest that level of anxiety and its behavioral realization depend on duration of aggressive experience and genetic strain.

Changes in blood biochemistry in mice during development of experimental depression

Biochemical parameters of the plasma were studied in mice at different stages of the development of depression-like states in males after social defeats in 10 and 20 intermale confrontations (T10 and T20 victims, respectively). Glucose and cholesterol levels were increased in T10 victims in comparison with intact animals. In T20 victims the increase in glucose level was paralleled by an increase in total protein. T20 victims differed from T10 victims by lower catalase activity.

[The effect of DAGO, selective milli-opioid receptor agonist, on hostile and anxious behaviors in male mice with different experience of aggression]

Effects of mu-opioid receptor agonist DAGO (2.0 mg/kg, s.c.) on anxioUs, hostile, and aggressive behaviors of male mice with repeated 3- and 20-day experience of aggression accompanied by victories (T3 and T20 winners, respectively) were stUdied. T20 winners showed lower aggression (attacking and biting) and hostile behavior and were more anxioUs (estimated by plUs-maze test) than T3 winners. In the plUs-maze test DAGO prodUced anxiogenic effects in intact males and was ineffective in T3 and T20 winners testifying to a decrease in mu-receptor sensitivity Under the inflUence of repeated aggression. In agonistic confrontation test, DAGO increased aggressive grooming in T20 winners, decreased hostile behavior (digging and throwing partner's litter) in T3 winners, and did not inflUence attacks in both groUps. It is sUggested that mu-opioid receptors are involved into forming the aggressive behavioral type in mice, and DAGO effects may be conditioned by emotional backgroUnd of these behavioral forms.

Behavioral effect of 1A-serotonin receptor agonist ipsapirone in mice previously defeated in male-male encounters

The effect of 1A-serotonin receptor agonist ipsapirone (3 mg/kg) on mouse behavior was studied in the "wall" and Porsolt tests. The effects of the test drug were compared in intact animals and mice previously defeated in 20 intermale encounters (victims). Ipsapirone was ineffective in victims and effective in intact mice in the wall test. In the Porsolt test the drug prolonged stupor in victims.

[Effect of long-term restraint stress on behavior of female C57BL/6J and CBA/Lac inbred mice. Dispersion and cluster analysis]

An augmented exploratory behaviour and motor activity and diminished anxiety after a restraint stress were found in CBA/Lac female mice [corrected] but not in C57BL/6J ones. In the Porsolt test the result was exactly opposite. A possibility of inherent anxiety-depressive pathological condition in the C57BL/6J mice [corrected] developing under the effect of repeated psychological stress, is assumed.

Fighting among C57BL/6J mice and its implications for [3H]8-hydroxy-N, N-dipropyl-2-aminotetralin binding in various brain regions

The binding of [3H]8-hydroxy-N, N-dipropyl-2-aminotetralin ([3H] 8-OH-DPAT) has been studied in various brain regions of male mice with the experience of repeated victory (winners) or defeat (losers) gained over 10 (T10) and 20 (T20) days of daily agonistic confrontations. The Bmax of [3H]8-OH-DPAT binding sites was found to be decreased in the hippocampus of the T20 winners when compared to the T10 winners or the control mice, and increased in the amygdala of the T20 losers. The Kd was increased in the amygdala of the T20 losers when compared to the animals of any other experimental group. No change in [3H]8-OH-DPAT binding was observed in the midbrain or the hypothalamus of the winners or losers. It was concluded that the 20-day agonistic confrontations, arranged in order to categorize the mice as winners or losers, had opposing effects on [3H]8-OH-DPAT binding.

Effect of enterosorbent noolith on behavior and serotonin (1A) receptors in mouse brain

Protective properties of a new enterosorbent noolith (lithium ions immobilized on mineral matrix) were studied in C57Bl/6J mice predisposed to depression caused by intermale confrontations. The drug was administered daily for 15 days after the 5th confrontation and then the animals were tested in the forced swimming test. The number of specific(3)H-8-OH-DPAT binding sites in 3 brain regions was determined. It is shown that noolith produced an antidepressive effect manifested in decreased immobility time in the Porsolt test. Moreover, noolith reduced the number of 1A-serotonin receptors in the frontal cortex and hypothalamus. It is concluded that noolith possesses protective properties.

[Analysis of possibility of genotypic correlation between fear and anxiety]

Special features of anxious behavior in the elevated plus maze test and acoustic startle response were analyzed in 11 inbred mouse strains. A significant influence of the genotype both on the startle amplitude and behavior in the elevated plus maze was found. However, analysis of covariance did not reveal a genotype-related association between anxiety and startle amplitude. The data indicates that the fear-induced acoustic startle response and anxious behavior in the elevated plus maze (agoraphobia) are not genetically related.

[Response of the serotoninergic brain system to social stress of various duration in male mice C57BL/6J and CBA/Lac]

The effects of social stress caused by experience of defeats in mice during 3 or 10 consecutive days of intermale confrontations on serotonergic brain activity (5-HT, 5-HIAA levels and 5-HIAA/5-HT ratio) in some brain regions of CBA/Lac (CBA) and C57BL/6J (C57) inbred mice have been studied. It was revealed the significant changes in 5-HT methabolism in the brain regions of defeated mice (losers) of CBA strain after 3 intermale confrontations. However, after 10 days of social stress these changes (excluded amygdala) turned to the control measures testifying to the adaptive mechanisms of serotonergic system in CBA losers. In C57 strain, the three-day social stress produced the mild changes in the brain serotonergic activity both quantitatively as well as qualitatively. Nevertheless, losers subjected to ten-day intermale confrontations had more expressed changes in 5-HT, 5-HIAA levels of 5-HIAA/5-HT ratios in the brain regions studied. It seems that long lasting social stress induced the development of disbalance of the brain serotonergic activity in C57 losers: it was shown the hyperactivity in the hypothalamus and hypoactivity in the amygdala and nucl. accumbens. Apparently, this cause leads to the development of the pronounced anxiety shown earlier in this mouse strain.

[Modifying effect of the repeated experience of agonistic confrontations on effect of naltrexone in male mice]

In mice with different experience of agonistic confrontations: victories or social defeats during 3 and 10 days (T3 and T10 winners and T3 and T10 losers, resp.), T10 winners displayed a lesser aggression and a more hostile behaviour than T3 winners. Naltrexone dose-dependently decreased attacks in the T3 winners and did not affect aggressive grooming, diggings, autogrooming, and exploratory activity. Naltrexone was ineffective in T10 winners. The naltrexone effects were similar in T3 and T10 losers and its high and low doses contrarily affected different parameters of submissive behaviour. The repeated experience of agonistic confrontations seems to modify the naltrexone effects depending on a neurochemical background, differing in winners and losers.

Features of the genetically defined anxiety in mice

The behaviors of male mice of the C57BL/6J (C57), CBA/Lac (CBA) and BALB/c (BALB) strains have been studied in the plus-maze and open field tests for estimation of state anxiety in the stressful novel conditions, and in the cubic box test (exploration of novel cubic box) and the partition test (behavioral reactivity to the unfamiliar partner in the neighboring compartment) for estimation of trait anxiety in the unstressful familiar conditions of the home cage. Plus-maze data suggest that C57 mice are the more anxious than CBA and BALB ones. However, it was revealed the opposite rank order in the open field. The study on the effect of pre-testing in the one of test on the behavior in the other test revealed active behavioral strategy in C57 mice in any situations. The plus-maze behavior of CBA mice was affected to a much lesser extent than in C57 ones after pre-testing in the open field, but expressed changes were observed in open field behavior of CBA mice after pre-testing in the plus-maze. BALB mice displayed low-reactive behavior after any pre-testing exposure under the state anxiety-provoking conditions. Familiar environment revealed a higher level of trait anxiety in C57 than males of other two strains: CBA and BALB mice willingly explore unfamiliar partner and cubic box while C57 mice avoid its. Mainly genetically inherent state anxiety in CBA mice and trait anxiety in C57 mice has been suggested. Lowest state and trait indices of anxiety were revealed in BALB mice in these conditions.

[The determination of the parameters of anxiety in C57BL/6J, CBA/Lac and BALB/c mice under the influence of a serotonin C1A receptor agonist [correction of antagonist]

Three strains of inbred mice, C57BL/6J (C57), CBA/Lac (CBA), and BALB/c (BALB) were examined in the elevated plus-maze after the injection of an anxiotropic drug, a 5-HT1A agonist ipsapirone (3 mg/kg; i.p.; 30 min). Treatment with ipsapirone had different anxiogenic effects on the behavior of mice in accordance with their genotype. In C57 mice the drug produced a significant decrease in the percentage of the open-arm time and the number of open-arm entries as well as in the number of full entries (when an animal was between the half and the end of an open-arm) and in the number of head dippings. Besides; the number of C57 mice which performed full entries after the ipsapirone injection decreased. In CBA mice ipsapirone reduced the number of enclosed-arm entries, the number of the passages from one enclosed arm to another and the number of head dippings. Only the number of passages dropped in BALB mice after the drug injection. Probably, just these parameters reflect anxiety in mice of the genotypes under study. It was suggested that the sensitivity of 5-HT1A receptors in C57 mice is the highest.

[The characteristics of the manifestation of hereditarily induced anxiety in male C57Bl/6J and CBA/Lac mice]

Behavior of male mice of C57Bl/6J and CBA/Lac strains was tested in the elevated plus-maze and open field in order to estimate state anxiety in novel conditions. The cube and partition tests were used to reveal trait anxiety in the familiar conditions of the home cage. It is concluded that genetically defined state anxiety is more pronounced in CBA/Lac mice and trait anxiety in C57Bl/6J strain.

[The behavior of mice from 6 genotypes in 2 tests for anxiety]

Mice from six inbred strains (CBA, ICR, SWR, BALB/c, DBA/2, and C57BL/6J) were tested for anxiety in elevated plus-maze and light-dark box. In the elevated plus-maze CBA, ICR, and SWR mice spent more time in the open area (open arms and the center of the maze) than BALB/c and, especially, DBA/2 and C57BL/6J mice. A significant negative correlation was revealed between the percent of time spent in the open area and the number of peepings from the enclosed arms. There was no correlation between the percent of the open-area time and the number of entries into the open arms. A positive correlation was found between the percent of the open-area time in the plus-maze test and percent of time spent in the white section of the light-dark box. Mice of SWR strain spent 64 percent of the experimental time in the white section, whereas C57BL/6J mice spent in the illuminated section of the box only 15 percent of time. A significant interaction was found between the main index of anxiety (percent of the open-area time in the box) and indices of exploratory activity (number of crossed squares and number of rearings) in the light-dark test.

[The participation of the brain dopamine D1 and D2 receptors in the process of the development of depression induced by social confrontations in mice]

Brain D1 and D2 receptors were studied in male mice with repeated experience of social defeats in daily intermale aggressive confrontations inducing development of experimental depression. Groups of animals were studied after 10 (T10 losers) and 20 (T20 losers) days of agonistic confrontations. Mice after 5 days of individual housing were used as a control group. In the experimental groups D1/D2 antagonist cisfluphentixol (0.2 mg/kg) did not affect the communicative behavior in the partition test that estimated behavioral reactivity of a male to another one. Selective D2 antagonist sulpiride (20 mg/kg), however, decreased these reactions in the control group and, in particular, in T10 losers but was ineffective in T20 losers. Both antagonists changed behavior in Porsolt's test of the control mice and, to a greater extent, of T10 losers but failed to change it in T20 losers. Decrease in Bmax in nucleus accumbens and increase in Kd in amygdala were revealed in T20 losers with [3H]-SCH 23390 binding assay. The obtained evidence shows that development of DISC is accompanied by D1 and D2 receptor sensitivity changes. Analysis of data suggests the specific participation of D1 receptors of the mesolimbic dopaminergic system at the stage of developed DISC.