The composition of peripheral immunocompetent cell subpopulations and cytokine content in the brain structures of mutant Disc1-Q31L mice

The DISC1 (disrupted in sсhizophrenia 1) gene is associated with brain dysfunctions, which are involved in a variety of mental disorders, such as schizophrenia, depression and bipolar disorder. This is the first study to examine the immune parameters in Disc1-Q31L mice with a point mutation in the second exon of the DISC1 gene compared to mice of the C57BL/6NCrl strain (WT, wild type). A flow cytometry assay has shown that intact Disc1- Q31L mice differ from the WT strain by an increase in the percentage of CD3+ T cells, CD3+CD4+ Т helper cells and CD3+CD4+CD25+ T regulatory cells and a decrease in CD3+CD8+ T cytotoxic/suppressor cells in the peripheral blood. A multiplex analysis revealed differences in the content of cytokines in the brain structures of Disc1-Q31L mice compared to WT mice. The content of pro-inflammatory cytokines was increased in the frontal cortex (IL-6, IL- 17 and IFNγ) and striatum (IFNγ), and decreased in the hippocampus and hypothalamus. At the same time, the levels of IL-1β were decreased in all structures being examined. In addition, the content of anti-inflammatory cytokines IL-4 was increased in the frontal cortex, while IL-10 amount was decreased in the hippocampus. Immune response to sheep red blood cells analyzed by the number of antibody-forming cells in the spleen was higher in Disc1-Q31L mice at the peak of the reaction than in WT mice. Thus, Disc1-Q31L mice are characterized by changes in the pattern of cytokines in the brain structures, an amplification of the peripheral T-cell link with an increase in the content of the subpopulations of CD3+CD4+ T helpers and CD3+CD4+CD25+ T regulatory cells, as well as elevated immune reactivity to antigen in the spleen.

Cytokine Production by Splenic Cells in C57BL/6J Mice with Depression-Like Behavior Depends on the Duration of Social Stress

We studied the influence of depression-like behavior developed in C57BL/6J mice under conditions of social stress of different duration on cytokine production by splenic cells. Imbalance of the pro- and anti-inflammatory cytokines was detected at the early stage of depression-like behavior (10-day experience of defeats): increased production of proinflammatory IL-2 and IL-6 cytokines along with a decrease in anti-inflammatory IL-10 level; the levels of IL-1β, TNFα, IFNγ, and IL-4 remained unaffected. At later terms (20 days of confrontations), we revealed more pronounced changes in spontaneous production of proinflammatory cytokines that were not detected after shorter social stress. These findings suggest that cytokine profile depends on duration of social stress. Possible mechanisms of cytokine production during formation of depression-like state are discussed.

Effect of Antidepressants on Immunological Reactivity in ASC Mice with Genetically Determined Depression-Like State

The effect of chronic treatment with antidepressant drugs fluoxetine (20 mg/kg) and imipramine (25 mg/kg) on the number of antibody-producing cells and the main T cell subpopulations in ASC mice characterized by genetic predisposition to depression-like states was studied at the peak of the SE-induced immune response (5×10(8)). Fluoxetine produced an immunostimulatory effect manifested in an increase in the relative and absolute number of IgM antibody-producing cells in the spleen and index of immunoreactivity (CD4/CD8). Administration of fl uoxetine to parental mouse strains without depression (CBA and AKR) had no effect (CBA) or reduced the immune response. The CD4/CD8 ratio did not increase under these conditions. Imipramine was ineffective in the correction of immune reactions in a depression-like state.

[Effect of dopamine D1 and D2 receptor blockade on the immunostimulating effect of δ1 opioid receptor agonist DPDPE in mice with different psychoemotional states]

It is established that activation of delta1 opioid receptors with their selective agonist DPDPE(100 μg/kg) significantly increases IgM immune response not only in C57BL/6J mice with unchanged psychoemotional state, but also in mice displaying aggressive or depressive-like behavior in the social stress model (10 days of agonistic confrontations). SCH-23390 (1.0 mg/kg), selective antagonist of dopamine D1 receptors, and selective D2 receptor blocker haloperidol (1 mg/kg) prevented the immunostimulating effect of DPDPE in animals not subjected to social stress. At the same time, both SCH-23390 and haloperidol did not affect DPDPE-induced immunostimulation in mice engaged in aggressive or depressive-like behaviors.

[Effect of antipsychotic amisulpride on immune reactivity]

The effect of atypical antipsychotic solian (amisulpride), binding predominantly to dopamine D2/D3-receptors, on the immune reactivity has been studied in mice of the CBA strain with different psychoemotional states (aggressive and submissive behavior). In addition, the effect of solian on the expression of various CD-markers of lymphocytes in has been analyzed in vitro for patients with schizophrenia diagnosis. Chronic (10 days) administration of solian in mice at a dose of 5.0 mg/kg resulted in a significant suppression of the immune response to T-dependent antigen (sheep red blood cells). This effect was manifested in animals with both psychoemotional states, but was more expressed in aggressive animals. In the in vitro system, solian produced opposite effects on the expression of surface CD receptors in lymphocytes of patients with schizophrenia. It is suggested that solian does not only affects immune function through D2 receptors of the brain, but also directly influences immunocompetent cells.

CLINICAL AND EXPERIMENTAL RESEARCH OF IMMUNOMODULATORY EFFECT OF AMISULPRIDE

Study of immunomodulatory effect of atypical antipsychotic amisulpride has revealed a positive clinical effect after 6-week therapy of schizophrenic patients regarding both positive and negative symptoms. A decrease in activity of humoral immunity factors (В lymphocytes, immunoglobulins, HLA-DR+-cells) identified among schizophrenic patients in the process of amisulpride therapy can be attributed to a positive effect optimizing the ratio Th1/Th2. Amisulpride when used under experimental conditions produced a suppression of IgM-immune response in mice of the C57BL/6J strain. This effect was more expressed in animals with aggressive behavior pattern. 

[Effect of activation of serotonin 5-HT1A-receptors on the immune response in mice of the ASC strain with depressive-like behavior]

Selective activation of serotonin 5-HT(1A)-receptors produced different effects on immunological reactivity in mice of ASC strain with genetic predisposition to depressive-like behavior, and parental CBA and AKR strains displaying no depressive reactions. Administration of 5-HT(1A)-receptors agonist 8-OH-DPAT at low dose (0.1 mg/kg) affecting upon presynaptic receptors resulted in immunostimulation in CBA mice and did not change the immune response level in mice of ASC strain. Activation of postsynaptic 5-HT(1A)-receptors with higher dose of 8-OH-DPAT (1.0 mg/kg) caused immunosuppression in CBA and AKR strains while under the same conditions the immune response of ASC mice was increased. Decrease the immune reactions in ASC mice was observed only after application of 8-OHDPAT at dose of 5 mg/kg. The changes of functional activity of pre- and postsynaptic 5-HT(1A)-receptors under a high predisposition to depressive-like behavior providing different effects of this receptor activation on immune function are discussed.

[T-lymphocyte subpopulations and immune response in mice of the ASC strain with depressive-like behaviour]

Analysis of the content of CD16/32+, CD4+ and CD8+ -cells was perfomed in the peripheral blood and spleen ofmice of the ASC strain with high predisposition to depressive-like state in comparison with mice of parent CBA strain having no depressive behaviour. In both cases, ASC mice showed a decrease in the percentage of CD16/32+ and CD4+-cells along with an increase CD8 cells and lowering of immunoreactivity index (CD4+/CD8+). Changes in cellular subpopulations found in intact ASC mice was accompanied with animals' low capacity to respond to T-dependent antigen: sheep red blood cells at the dose of 5 x 10(8). In contrast to CBA mice the percentage and absolute number of IgM-antibody-forming cells were significantly decreased in the spleen of ASC mice on the 4th and 5th days after immunization as well as the numbers of IgG-antibody-forming cells on the 6th day of the immune response. Possible mechanisms underlying the immune reactivity inhibition under depressive-like state are discussed.

[Clinical and experimental research of immunomodulatory effect of amisulpride]

Study of immunomodulatory effect of atypical antipsychotic amisulpride has revealed a positive clinical effect after 6-week therapy of schizophrenic patients regarding both positive and negative symptoms. A decrease in activity of humoral immunity factors (B lymphocytes, immunoglobulins, HLADR(+)-cells) identified among schizophrenic patients in the process of amisulpride therapy can be attributed to a positive effect optimizing the ratio Th1/Th2. Amisulpride when used under experimental conditions produced a suppression of IgM-immune response in mice of the C57BL/6J strain. This effect was more expressed in animals with aggressive behavior pattern.

[Role of serotonin receptors in the delta-opioid immunosuppression]

The present study indicates involvement of serotoninergic (5-HTergic) mechanisms in immunosuppression by DSLET (100 mkg/kg), a selective agonist of the delta2-opioid receptors, in CBA mice. 8-OH-DPAT (0.1 mg/kg), a selective agonist of the 5-HT(1A)-autoreceptors, WAY-100635 (1, 3 mg/kg) and ketanserin (1, 3 mg/kg), a selective antagonists of the postsynaptic 5-HT(1A)- and 5-HT(2A)-receptors, respectively, prevented immunosuppressive effect of DSLET. A possible differential role for 5-HT-receptors in delta-opioid immunosuppression is suggested.

[Immune response under activation of pre- and postsynaptic serotonin 5-HT1A-receptors in mice with depressive-like behavior]

Development of depressive-like state in mice of the C57BL/6J strain is accompanied by a considerable decrease in the immune response. A selective activation of presynaptic 5-HT1A-receptors (8-OH-DPAT, 0.1 mg/kg, for 15 min before immunization) markedly increased the immune response tested with the number of IgM-antibody-forming cells, and stimulation of postsynaptic 5-HT1A-receptors (8-OH-DPAT, 1.0 mg/kg, for 30 min before immunization twice) produced an immune suppression in control animals (mice without experience of victories and defeats). On the other hand, there were no changes in the immune response level following 8-OH-DPAT administration (0.1 and 1.0 mg/kg) in mice with depressive-like state. The role of pre- and postsynaptic 5-HT1A-receptors in immunomidulation in mice with depressive-like behaviour is discussed.

[Mu-opioidergic immunomodulation: the neurochemical basis]

The review summarizes information from literature and results of autor's own investigation concerning the influence of the selective mu-opioid agonists (beta-endorphin, morphine, DAGO) on immune status. The neurochemical mechanisms of the interaction between the mu-opioidergic and neuromediator systems are discussing. The participation of the dopaminergic mechanisms in mu-opioid-induced changes of immunological reactivity is revealed also.

[Effects of chronic fluoxetine treatment on catalepsy and immune response in mice genetically predisposed to freezing reaction: the role of 5-HT1A and 5-HT2A receptors and tph2 and SERT genes]

ASC/Icg (Antidepressant Sensitive Catalepsy) mouse strain selected for high predisposition to pinch-induced catalepsy is characterized by depressive-like behavior and impaired immune response. Chronic treatment with SSRI fluoxetine attenuated catalepsy manifestation and normalized a decreased number of rosette-forming cells (RFC) in spleen in ASC mice. Chronic fluoxetine administration had no effect on catalepsy and RFC number in mice of parental cataleptic CBA/Lac strain. Fluoxetine failed to alter 5-HT1A receptor functional activity in mice of both strains and diminished 5-HT2A receptor functional activity in CBA but not in ASC mice. No effect on cortical 5-HT1A and 5-HT2A receptor mRNA levels and on 5-HT1A receptor, tph2 (tryptophan hydroxylase-2) and SERT (serotonin transporter) mesencephalic gene expression was observed in ASC mice. Other possible serotonergic mechanisms of fluoxetine effect on catalepsy and immune response in mice with depressive-like state are discussed.

[Involvement of presynaptic 5-HT1A receptors in immunomodulation under conditions of psychoemotional state]

The development of the immune reaction after the activation or blockade of presynaptic 5-HT1A receptors, respectively, with a selective agonist or antagonist depends on specific behavioral patterns. Agonist of 5-HT1A receptors 8-OH-DPAT (0.1 mg/kg 15 min prior to immunization) did not change the number of IgM plaque-forming cells in the spleen of aggressive mice at the peak of the immune response (the 4-th day after immunization) but increased their number in submissive animals, in which the baseline immune response was lower than in aggressive animals. Administration of WAY-100635 (0.1 mg/kg 30 min prior to immunization) resulted in a decrease in the immune reaction in aggressive mice and led to its increase in submissive animals. It is suggested that the immunomodulatory effects of drugs affecting the activity of presynaptic 5-HT1A receptors are related to changes in the functional state of these receptors and the interaction between serotonin- and dopaminergic systems.

[Impact of serotonin 1A receptors in the kappa-opioid immunosuppression]

The data obtained indicate that rimorphin (0.1 mg/kg), a specific kappa-agonist, evoked a significant inhibition of the immune response in CBA mice. Pretreatment of the animals with 8-OH-DPAT (0.1 mg/kg), a selective serotonin (5-HT) agonist, activating presynaptic 5-HT(1A) receptors, or WAY-100635 (1.0 mg/kg), a selective 5-HT(1A) receptors blocker of postsynaptic 5-HTIA receptors, prevents kappa-opioid effect. The present data indicate that kappa-opioid-induced immunosuppression is due to the involvement of the 5-HT-ergic mechanisms that are modulated via pre- and postsynaptic 5-HT(1A) receptors.

The differential contribution of dopamine D(1) and D (2) receptors to mu-opioidergic immunomodulation

Activation of mu-opioid receptors (mu-OR) by the highly selective agonist DAGO (100 microg/kg) significantly increased the immune response in CBA mice. This effect of the mu agonist was prevented by prior blockade of dopamine D(2) receptors with haloperidol (2 mg/kg). In contrast, the selective D(1) receptor antagonist SCH 23390 (1 mg/kg) had no effect on the nature of the immune reaction in response to antigen (sheep erythrocytes, 5 x 10(8) cells). However, blockade of both types of dopamine receptor led to the same effect--immunosuppression. These data lead to the suggestion that D(1) and D(2) receptors make different contributions to modulating immunogenesis on activation of mu-OR.

[Presynaptic 5-HT1A receptors in immunomodulation]

It is shown that a selective agonist of 5-HT1A receptors 8-OH-DPAT in a low dose (0.1 mg/kg), which is known to affect mainly the presynaptic 5-HT1A receptors increased the immune response at the peak of reactions (the forth or fifth day after immunization with sheep red blood cells - SRBC) in CBA mice and Wistar rats. Treatment of the animals with the drug 15 min prior to antigen injection raised the number of plaque-forming cells (lgM-PFC) and rosette-forming cells (RFC) in the spleen. The preliminary blockade of 5-HT1A receptor with a selective antagonist of 5-HT1A receptors WAY-100635 (0.1 mg/kg) prevented the immunostimulating effect of 5-HT 1A receptors agonist 8-OH-DPAT, whereas WAY-100635 administration alone in the same dose didn't change the immune response. Activation of 5-HT1A receptors under conditions of electrical lesion of 5-HTergic neurons of the nucleus raphe was unable to enhance the immune reactions, as it did in sham-operated rats. The data obtained indicate that the somatodendric 5-HT1A autoreceptors are involved in immunomodulation.

Effects of activation and blockade of dopamine D2 receptors on the immune response in mice with different types of behavior

Activation of dopamine D(2) receptors by the selective agonist quinpirole was found to lead to immunostimulation in control (no experience of confrontations) C57BL/6J mice and in mice subjected to psychoemotional tension (aggression and submission). The most marked increase in the immune response was seen on formation of the aggressive and submissive behavioral strategies. The effects of blockade of D(2) dopamine receptors by haloperidol-immunosuppression-were seen only in control and aggressive animals, but were not seen in animals with submissive behavior. The question of the significance of the initial psychoemotional state, which is linked with particular neurotransmitter patterns in the brain (levels of dopamine, serotonin, their metabolites; dopamine receptor activity in subcortical structures), for the effects of agents altering the activity of dopamine D(2) receptors on the immune response is discussed.

Significance of initial emotional state for neuroimmunomodulation in conditions of activation and blockade of 5-HT1A receptors

Experiments performed on male CBA mice immunized with sheep erythrocytes at a dose of 5 x 10(8) cells showed that the selective agonist of serotonin 5-HT(1A) receptors 8-OH-DPAT (1 mg/kg) suppresses the immune response in aggressive animals. In mice demonstrating the submissive type of behavior, formed during 10 days of experience of defeats, activation of 5-HT(1A) receptors with 8-OH-DPAT had no effect on the immune response. However, treatment with the selective 5-HT(1A) receptor blocker WAY-100635 stimulated the immune response, but only in submissive mice. These data lead to the conclusion that activation and blockade of 5-HT(1A) receptors have different effects on the immune response in CBA mice depending on the initial emotional state of the animals, due to different activities of neurotransmitter systems, particularly the serotoninergic, in aggressive and submissive mice.

[Effect of the activation and blockade of D2 dopamine receptors on the immune response in mice with different types of social behavior]

Activation of D2 dopamine receptors with a selective agonist quinpirol in C57BL/6J mice was found to induce increase in the immune response regardless of the initial psychoemotional state of animals, e. g. in aggressive mice, submissive mice, and mice without victory or defeat experience (control). However, the immune response level in aggressive and submissive mice was significantly higher than that of control animals. At the same time, the blockade of D2 dopamine receptors with haloperidol suppressed immunogenesis in aggressive and control mice, whereas the immune reactions in submissive mice were unchanged. Thus, the effect of activation and blockade of D2 dopamine receptors on immune function is dependent on the initial psychoemotional status of animals which to a greater extent might be provided by the neuromediator pattern of the brain and activity of DA receptors.

[Differential contribution of dopamine D1 and D2 receptors in the mu-opioidergic immunomodulation]

The study has shown that activation of mu-opioid receptors by a highly selective agonist DAGO (100 microg/kg) results in a significant increase of the immune response to antigen (SRBC, 5% 10(8)) in CBA mice. Haloperidol (2 mg/kg), a selective antagonist of the postsynaptic dopamine (DA) receptors, prevented immunostimulating effect of DAGO. In contrast, selective D1--antagonist SCH 23390 (1 mg/kg) did not affect on DAGO-induced enhancing of immune reactivity. At the same time, the blockade of both types of DA receptors (D1 and D2) caused similar immunosuppressing effects. These data suggest a possible differential role for D1 and D2 receptors in mu-opioidergic immunomodulation.

[Significance of initial emotional state for neuroimmunomodulation under conditions of activation or blockade of 5-HT1A receptors]

Selective agonist of 5-HT1A receptors--8-OH-DPAT (1 mg/kg) induced a suppression of the immune reaction in aggressive male CBA mice immunized with SRBC (5 x 10(8)). In submissive mice with 10-day defeat experience in confrontation tests, the activation of 5-HT1A receptors with 8-OH-DPAT did not alter the immune response, whereas the application of selective antagonist of 5-HT1A receptors WAY-100635 increased the immune reaction only in submissive mice. It is concluded that activation or blockade of 5-HT1A receptors produced different effects on the immune function of CBA mice depending on the initial emotional state which is known to be provided in aggressive and submissive animals by different activities of the brain neurotransmitter systems including the 5-HTergic system.

Effect of Dexamethasone on Immune Response of Mice with Different Behavioral Types

Experiments on a model of paired sensory contact showed that dexamethasone effectively suppressing the response to ACTH not only prevented immunosuppression in male C57Bl/6J mice with submissive behavior formed during different periods of confrontation testing (days 10 and 20), but also stimulated the immune response in comparison with the control. Immune response in aggressive animals after 20-day confrontations was higher than in controls and submissive mice and did not change after dexamethasone injection. The authors conclude that the immunosuppressive effect in submissive animals is realized through ACTH, which little contributes into immunomodulation in aggressive mice.

[Activation and blocking of 5-HT1A receptors influence on the immune response in CBA mice]

5-HT1A type serotonin receptors influence the immunomodulating action of the selective preparations 8-OH-DPAT (5-HT1A receptor agonist) and WAY-100635 (5-HT1A receptor antagonist) in CBA mice. The activation of 5HT1A receptors with 8-OH-DPAT (1 mg/kg) decreased, while their blocking with WAY-100635 (1 mg/kg) increased the reaction intensity at the peak of response to immunization with ram erythrocytes. Preliminary blocking of the 5-HT1A receptors with WAY-100635 prevented the inhibiting action of 8-OH-DPAT.

Stimulation of the Immune Response During Activation of the Dopaminergic System in Mice with Opposite Types of Behavior

Studies reported here demonstrated that activation of the dopaminergic system induces increases in the immune response regardless of the type of behavior in mice (line CBA), i.e., in aggressive mice, submissive mice, and mice lacking experience of victory or defeat (controls). Changes in the activity of the dopaminergic system were induced with SKF-38393, a selective agonist of dopamine D1 receptors, and with p-chlorophenylalanine (PCPA), which we have previously shown to activate D2 receptors. In the aggressive form of behavior, which was characterized by strong (compared with controls) immune responses, SKF-38393 and PCPA led to further increases in the immune response. In submissive mice, activation of the dopaminergic system altered the nature of the immune response, with immunostimulation, as in aggression. It is suggested that activation of the dopaminergic system in conditions of defined psychoemotional status fixed by acquisition of opposite types of behavior, induces the formation of a new neurochemical pattern--the dopaminergic set--which led to changes in the nature and intensity of the immune response.

Nature of the distribution of serotonin and a serotonin metabolite in brain structures and the development of immunosuppression in submissive mice

Studies of C57BL/6J mice with acquired submissive behavior in a sensory contact model demonstrated increases in serotonin (5-HT) levels in the amygdaloid complex, hippocampus, the dopaminergic nuclei A11, A10, and A9, and in the caudate nucleus and hypothalamus, compared with controls, after 10 and 20 days of confrontations. Levels of the 5-HT metabolite 5-hydroxyindoleacetic acid (5-HIAA) in most structures were significantly higher after 20 days of confrontations than after 10 days. Increases in the 5-HIAA/5-HT ratio in the cervical nuclei of the midbrain, nucleus accumbens, A9, and hypothalamus as compared with controls were seen in mice with 10 and 20 days of confrontations. Immunization of mice on days 10 and 20 of confrontations showed suppression of immune responses as compared with controls, while immune measures reached control values by 40 days of experience of defeat. Thus, experience of 10 days of defeat led to immunosuppression on a background of activation of the 5-HT system in a series of brain structures: the cervical nuclei of the midbrain, the nucleus accumbens, and A9. As confrontations continued, there were decreases in the 5-HIAA/5-HT ratio on these structures, along with a tendency for immune responses to increase.

[Activation of dopaminergic system stimulates an immune response in mice with opposite type of behaviour]

It was shown that activation of dopaminergic (Daergic) system induced an increase of the immune responsiveness independent of the CBA mice behaviour typeanimals without experience of victories and defeats (control), with aggression and submission. Administration of SKF-38393, a selective agonist of DA D1-receptors, resulted in enhanced immune response as tested by plaque-forming cells and rosette-forming cells number. Similar immunostimulation was observed after injection of p-chlorophenylalanine realizing its influence on the immune response through DA D2-receptors as shown by us elsewhere. It was suggested that activation of Da-ergic system produces a new neurochemical pattern (Daergic neurochemical set) which are responsible for character and intensity changes of the immune response in mice with alternative form of social behaviour.

[Distribution of serotonin and its metabolites in the brain structures and immunosuppression in submissive mice]

The development of submissive behaviour in C57BL/6J mice in the sensory contact model was associated with an increase in the content of serotonin (5-HT) in the amygdala, hippocampus, dopaminergic nuclei A11, A10, A9, as well as in the caudate nucleus and hypothalamus after 10 and 20 days of confrontations compared to the controls. The level of 5-HT metabolite 5-hydroxyindolacetic acid (5-HIAA) was significantly higher in the most structures examined after 20 daily encounters as compared to animals with experience of 10 confrontations. The time course of submission over 10 or 20 days resulted in an increase of 5-HIAA/5-HT ratio in the midbrain nucleus raphe, nucleus accumbens, A9 and hypothalamus. In mice immunised on the 10th or 20th day of confrontations, the immune response inhibition was observed while its level remained unchanged after more prolonged confrontations (40 days). Thus, the experience of defeats during 10 days shown to be accompanied with an activation of 5-HT system in a number of the brain structures, produced immunosuppression. With increasing number of confrontations the ratio 5-HIAA/5-HT was decreased in the same structures and a tendency to the immune response elevation appeared.

Effects of type 1A serotonin receptor agonist 8-OH-DPAT on immune response

The selective agonist of type 1 A serotonin receptors 8-hydroxy-2-(di-n-propyl-amino)tetra-lin (8-OH-DPAT) suppressed the immune response. Intraperitoneal administration of 1 mg/kg 8-OH-DPAT to Wistar rats over 2 days after immunization decreased the count of plaque- and rosette-forming cells on day 5. Our results indicate that type 1A serotonin receptors are involved in the realization of the immunosuppressive effects of the serotoninergic system.

[Involvement of dopaminergic systems in the functional specialization of brain areas during formation of aggressive and submissive behavior in mice]

In addition to its common activating action, the DA system is involved in the functional specialization of the brain areas which participate in the expression of discrete behavioral components. The evidence for different levels of activity of the mesocortical DA system in aggressive and submissive mice were obtained. In C57BL/6J mice, confrontations produced simultaneous increase in the extracellular DA content and its release from the nerve terminals in the nucleus accumbens and frontal cortex, while an elevation of the HVA concentration in these structures was found only in submissive mice. After 20 encounters, the habituation of animals to the repeated stress exposures and conditioning developed. Activation of the DA metabolism (increase in the DOPAC level and DOPAC/DA ratio) in the hippocampus was observed only in aggressive mice after 20 days of confrontation, when the extinction of the information novelty leading to aggression had been already accomplished. Our findings suggest the predominance of the role of the mesolimbic DA system, in particular, of its mesoaccumbens link, in the extinction of the information novelty in aggressors. A role of the mesocortical DA system in realization of the submissive behavior patterns, stress reactions, conditioned defensive behavior, anxiety-related behavior, and in modulation of the anxiety response to social stimuli is considered.

Brain content of 5-hydroxytryptamine and 5-hydroxyindoleacetic acid and immune response in aggressive C57bl/6J mice

Catabolism of 5-hydroxytryptamine in the midbrain raphe nuclei of aggressive C57Bl/6J mice increased after 10 and 20 days of confrontations. Both catabolism and concentration of 5-hydroxytryptamine increased in the dopaminergic nuclei A11, A10, A9, and in the amygdala. The level of 5-hydroxyindoleacetic acid in the A9 and raphe nuclei decreased after 20 days of confrontations, which coincided with manifestation of the immune response.

[Effect on the immobilization-induced stress on the immune response in mice with various behavioral stereotypes]

CBA and C57BL/6J mice with aggressive and submissive types of zoo-social behavior fixed during 10-day confrontation testing demonstrated different immune response to immobilization stress. In aggressive mice with confrontation experience stress resulted in a decrease in the immune response in comparison with aggressive inexperienced mice. Therewith, the immune response of CBA mice did not differ from the control level (the immunized mice without experience of victories and defeats), and in C57BL/6 mice the immune response was two times lower than in the control. In contrast to the control and aggressive mice, stress did not suppress the immune response in submissive animals. It is suggested that stress-induced changes in the immune response depend on zoo-social rank of an individual underlain by a particular neurochemical pattern of the brain.

[The neurochemical set of the brain--an extra-immune mechanism of psychoneuroimmunomodulation]

The present study provides evidence for involvement of brain neurotransmitters in the control of an immune response. The extra-immune mechanism of immunomodulation is considered by analyzing drug-induced changes in the brain neurotransmitter systems, brain destruction, altered activity of brain regions due to psychoemotional stress, including mental disease. It is suggested that the pattern of neurotransmitter activity with its prevalence in certain brain regions determines the neurochemical set-up of the brain for psychoneuroimmunomodulation, i.e. its extra-immune mechanism.

[Changes in the number of CD4+ T-helpers in the bone marrow of aggressive mice of C57BL/6J and CBA strains]

Aggressive behaviour led to immunostimulation with a subsequent rise in the number of T-helpers in C57B1 and CBA mice. The number of CD4+ T-helpers in their bone marrow correlated with duration of successive experience of victories. The effect of such a behaviour on immunity seems to be due to an activation of the dopaminergic system.

[Effect of opioid peptides on immunomodulation]

Activation of the opioid receptors by delta-agonist DSLET and by kappa-agonist rimorphin led to a significant inhibition of plaque-forming and rosette-forming cells in the CBA mice. On the other hand, mu-agonist DAGO stimulated the immune response on the 4th and 5th days after immunization with SRBC (5 x 10(8)). Lesion of the hypothalamo-hypophyseal connection prevented immuno-stimulating as well as immuno-depressive effects. The latter seems to be due to an interaction with the serotoninergic system, whereas immuno-stimulating effect involves the dopaminergic system.

Participation of opiate delta-receptors in immunomodulation

The activation of the opiate delta-receptors by the highly specific agonist DSLET evokes an immunoinhibitory effect in CBA mice which disappears with preliminary blockade of S2 serotonin receptors by cyproheptadine. The blockade of delta-receptors by the antagonist ICI 174,864 leads to stimulation of the immune response, which is tested on the basis of the number of rosette-forming cells. Neither stimulation nor suppression of immunogenesis are manifested in animals with a transsected hypophyseal stalk; this suggests the central action of the opioids. The increase in the immune response obtained with the administration of ICI 174,864 is associated with the dopaminergic system, since it is prevented by haloperidol. It was demonstrated that the thymus participates in the immune-stimulating influence of ICI 174,864.

[The participation of the delta opioid receptors in immunomodulation]

The delta-receptors agonist DSLET inhibited immune responses in the CBA mice. The immunosuppression was shown to be due to an interaction with the serotoninergic system. No immunostimulating effect of the delta-opioid receptors antagonist ICI 174,864 occurred in the animals with dissection of the pituitary stalk. The immunostimulation was shown to be realised via the thymus and prevented by a preliminary haloperidol blockade of the D-2 dopaminergic receptors. The cerebral delta-opioid receptors seem to participate in neuro-immunomodulation through the interaction with the serotonin and dopamine neurotransmitter systems.

[The normalization of the immune response in old stressed mice by apomorphine]

It has been shown that the immune reactivity of old C57BL/6 mice aged 24-27 months immunized with sheep red blood cells (5 x 10(8)) was decreased as compared to young mice (2-3 months). Activation of the dopaminergic system by the agonist of dopamine postsynaptic receptors apomorphine resulted in normalization of an immune response in old mice. Injection of apomorphine also prevented the immunosuppression observed in old mice, which was induced by immobilization stress (3.5 hours on the back). Immune response level of these animals approached that of young nonstressed animals. It was suggested that disturbance of the mechanisms of psychoneuroimmunomodulation in old and stressed animals could be prevented by changing the neurochemical pattern of the brain.