[Functional Responses to the Chronic Activation of 5-HT1A Receptors in Mice with Genetic Predisposition to Catalepsy].

The effects of chronic 5-HT1A receptor activation on the behavior, functional activity of 5-HT1A receptors, and expression of key genes of the brain 5-HT system were studied in mice of the catalepsy-prone CBA strain and the catalepsy-resistant C57BL/6 strain. Chronic treatment with 8-Hydroxy-2-(di-n-propyl-amino)tetralin (8-OH-DPAT) (1.0 mg/kg i.p., 14 days) led to a significant decrease in the hypothermic response to acute administration of 8-OH-DPAT in CBA and C57BL/6 mice, which indicates the desensiti-zation of 5-HT1A receptors in both strains. Pretreatment with the 5-HT7 receptor agonist SB 269970 did not affect the hypothermic response to the acute administration of 8-OH-DPAT, which suggests an independent functional response of 5-HT1A receptors. The treatment did not induce any changes in the behavior in the open field paradigm in CBA mice, but significantly increased the total path, the time spent in the center, and the number of rearings in C57BL/6 mice, which indicates the enhancement of locomotor and exploratory activity in C57BL/6 mice. The chronic activation of 5-HT1A receptor downregulated 5-HT1A gene expression, as well as the expression of the gene that encodes tryptophan hydroxylase 2, a key enzyme of 5-HT biosynthesis, in the midbrain and the expression of the gene that encodes the 5-HT2A receptor in the frontal cortex of CBA, but not C57BL/6 mice. The obtained data provide a new evidence on the receptor-gene cross talk in the brain 5-HT system that may underlie the loss of pharmacological efficacy of 5-HT1A receptor agonists. In turn, the loss of the behavioral response and compensatory alterations in key genes of the brain 5-HT system in CBA mice suggests that catalepsy-prone and -resistant genotypes demonstrate different sensibility to the effects of drugs.

[The Effects of Chronic Alcoholization on the Expression of Brain-Derived Neurotrophic Factor and Its Receptors in the Brains of Mice Genetically Predisposed to Depressive-Like Behavior].

Brain-derived neurotropic factor (BDNF) plays an important role in mechanisms of depression. Precursor protein of this factor (proBDNF) can initiate apoptosis in the brain, while the mature form of BDNF is involved in neurogenesis. It is known that chronic alcoholization leads to the activation of apoptotic processes, neurodegeneration, brain injury, and cognitive dysfunction. In this work, we have studied the influence of long-term ethanol exposure on the proBDNF and BDNF protein levels, as well as on the expression of genes that encode these proteins in the brain structures of ASC mice with genetic predisposition to depressive-like behavior and in mice from parental nondepressive CBA strain. It was shown that chronic alcoholization results in a reduction of the BDNF level in the hippocampus and an increase in the amount of TrkB and p75 receptors in the frontal cortex of nondepressive CBA mice. At the same time, the long-term alcoholization of depressive ASC mice results in an increase of the proBDNF level in the frontal cortex and a reduction in the p75 protein level in the hippocampus. It has also been shown that, in depressive ASC mice, proBDNF and BDNF levels are significantly lower in the hippocampus and the frontal cortex compared with nondepressive CBA strain. However, no significant differences in the expression of genes encoding the studied proteins were observed. Thus, changes in the expression patterns of proBDNF, BDNF, and their receptors under the influence of alcoholization in the depressive ASC strain and nondepressive CBA strain mice are different.

[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.

[Influence of chronic alcohol treatment on the expression of the Bdnf, Bax, Bcl-xL, and CASP3 genes in the mouse brain: Role of the C1473G polymorphism in the gene encoding tryptophan hydroxylase 2].

Tryptophan hydroxylase 2 (Tph-2) is the key enzyme in serotonin biosynthesis. Serotonin is one of the main neurotransmitters involved in the regulation of various physiological functions and behavior patterns. The influence of chronic ethanol consumption on the expression of the Bdnf, Bax, Bcl-xL, and CASP3 genes was studied in the brain structures of B6-1473C (C/C) and B6-1473G (G/G) mice that had been obtained on the base of the C57BL/6 strain. The strains differed in the genotype for the C1473G single nucleotide polymorphism in the Tph-2 gene and in Tph-2 enzyme activity. It was found that chronic alcohol treatment led to a significant increase in the expression of the Bdnf gene in the midbrain of B6-1473G mice, but not in B6-1473С. Chronic alcohol treatment considerably decreased the expression of the ultimate brain apoptosis effector, caspase 3, in the frontal cortex, but increased it in the hippocampus of B6-1473G mice. At the same time, chronic ethanol administration reduced the level of the antiapoptotic Bcl-xL mRNA in the midbrain of B6-1473C mice. Thus, the C1473G polymorphism in the Tph-2 gene considerably influenced the changes in the expression patterns of genes involved in the regulation of neurogenesis and neural apoptosis induced by chronic ethanol treatment.

Effect of microgravity on glial cell line-derived neurotrophic factor and cerebral dopamine neurotrophic factor gene expression in the mouse brain.

UNLABELLED: Mice were exposed to 1 month of space flight on the Russian biosatellite BION-M1 to determine its effect on the expression of genes involved in the maintenance of the mouse brain dopamine system. The current article focuses on the genes encoding glial cell line-derived neurotrophic factor (GDNF) and cerebral dopamine neurotrophic factor (CDNF). Space flight reduced expression of the GDNF gene in the striatum and hypothalamus but increased it in the frontal cortex and raphe nuclei area. At the same time, actual space flight reduced expression of the gene encoding CDNF in the substantia nigra but increased it in the raphe nuclei area. To separate the effects of space flight from environmental stress contribution, we analyzed expression of the investigated genes in mice housed for 1 month on Earth in the same shuttle cabins that were used for space flight and in mice of the vivarium control group. Shuttle cabin housing failed to alter the expression of the GDNF and CDNF genes in the brain structures investigated. Thus, actual long-term space flight produced dysregulation in genetic control of GDNF and CDNF genes. These changes may be related to downregulation of the dopamine system after space flight, which we have shown earlier. © 2015 Wiley Periodicals, Inc. SIGNIFICANCE: Our results provide the first evidence of microgravity effects on expression of the GDNF and CDNF neurotrophic factor genes. A considerable decrease in mRNA level of GDNF and CDNF in the nigrostriatal dopamine system was found. Because both GDNF and CDNF play a significant role in maintenance and survival of brain dopaminergic neurons, we can assume that this dysregulation in genetic control of GDNF and CDNF genes in substantia nigra could be among the reasons for the deleterious effects of space flight on the dopamine system.

[The effect of central administration of the neurotrophic factors BDNF and GDNF on the functional activity and expression of the serotonin 5-HT2A receptors in mice genetically predisposed to depressive-like behavior].

Brain serotonin (5-HT) system plays an important role in the control of normal and pathological behavior. 5-HT2A receptors are widely implicated in the regulation both normal functions and psychopathologies, especially schizophrenia and depression. Here, we investigated implication of 5-HT2A receptor in mechanisms of neurotrophic factors BDNF and GDNF action. We found that the acute intracerebroventricular injection of BDNF produced considerable increase in 5-HT2A receptor functional activity in ASC mice. Moreover, BDNF injection led to the increasing of 5-HT2A receptor gene expression in the hippocampus and its decrease in the frontal cortex without any effects in the midbrain. On the contrary, GDNF injection failed to alter 5-HT2A receptor functional activity, but increased the 5-HT2A receptor gene expression in the frontal cortex without any effects in the hippocampus and midbrain. Thus, an effect of the central administration of the neurotrophic factors BDNF and GDNF on the 5-HT2A receptor functional activity and gene expression was shown. The results indicate the implication of 5-HT2A receptor in the mechanisms of BDNF and GDNF action.

[Effect of GDNF on the behavior of ASC mice with high hereditary predisposition to catalepsy].

ASC mice, which were selected for high predisposition to catalepsy, are convenient genetic model for research of central mechanisms related to disorder of motor regulation. The aim of the work was to study the effect of glial cell line-derived neurotrophic factor (GDNF) on catalepsy, locomotor activity, stereotyping behavior in the marble burying test and on the dopamine level in striatum of ASC mice. It was shown that GDNF increased the locomotor activity in the open field, reduced catalepsy expression and stimulated the stereotyping obsessive-compulsive behavior. These changes in behavior were accompanied by increasing dopamine level in striatum.

[Implication of 5-HT2A receptors in the genetic mechanisms of the brain 5-HT system autoregulation].

Brain serotonin (5-HT) system has been implicated in pathophysiology of anxiety, depression, drug addiction, and schizophrenia. 5-HT2A receptor is involved in the mechanisms of stress-induced psychopathology and impulsive behavior. Here, we investigated the role of 5-HT2A receptor in the autoregulation of the brain 5-HT system. The chronic treatment with agonist of 5-HT2A receptor DOI (1.0 mg/kg, i.p./14 days) produced considerable decrease of 5-HT2A receptor-mediated "head-twitches" in AKR/J mice indicating desensitization of 5-HT2A receptors. Chronic DOI treatment failed to alter 5-HT2A receptor gene expression in the midbrain, hippocampus and frontal cortex. At the same time, the increase in the expression of the gene encoding key enzyme of 5-HT synthesis, tryptophan hydroxylase 2 (TPH2), the increase in TPH2 activity and 5-HT levels and decreased expression of serotonin transporter (5-HTT) gene was found in the midbrain of DOI-treated mice. The results provide new evidence of receptor-gene cross-talk in the brain 5-HT system and the implication of 5-HT2A receptor in the autoregulation of the brain 5-HT system.

[On the role of selective silencer Freud-1 in the regulation of the brain 5-HT(1A) receptor gene expression].

Selective 5-HT(1A) receptor silencer (Freud-1) is known to be one of the main factors for transcriptional regulation of brain serotonin 5-HT(1A) receptor. However, there is a lack of data on implication of Freud-1 in the mechanisms underlying genetically determined and experimentally altered 5-HT(1A) receptor system state in vivo. In the present study we have found a difference in the 5-HT(1A) gene expression in the midbrain of AKR and CBA inbred mouse strains. At the same time no distinction in Freud-1 expression was observed. We have revealed 90.3% of homology between mouse and rat 5-HT(1A) receptor DRE-element, whereas there was no difference in DRE-element sequence between AKR and CBA mice. This indicates the absence of differences in Freud-1 binding site in these mouse strains. In the model of 5-HT(1A) receptor desensitization produced by chronic 5-HT(1A) receptor agonist administration, a significant reduction of 5-HT(1A) receptor gene expression together with considerable increase of Freud-1 expression were found. These data allow us to conclude that the selective silencer of 5-HT(1A) receptor, Freud-1, is involved in the compensatory mechanisms that modulate the functional state of brain serotonin system, although it is not the only factor for 5-HT(1A) receptor transcriptional regulation.

[The role of the glycoprotein gp130 in serotonin mediator system in mouse brain].

Glycoprotein gp130 is involved in signaling out of significant cytokine receptors as interleukin-6 (IL-6), leukemia inhibitory factor and ciliary neurotrophic factor, which play critical role in immunity, inflammation and neurogenesis. IL-6 and brain neurotransmitter serotonin are involved in the mechanism of depression. The aim of this work was to investigat the role of protein gp130 in the regulation of expression of genes, coding the key enzyme of serotonin synthesis--tryptophan hydroxylase 2 (TPH2), 5-HT-transporter, 5-HT(1A)- and 5-HT(2A)-receptors of serotonin. The study was carried out on adult mouse males of AKR and congenic AKR.CBA-D13Mit76 strains, created by transfer of the fragment of chromosome 13 containing the gene coding gp130 protein from CBA/Lac strain to the genome of AKR/J strain. Decreased expression of 5-HT(1A) - 5-HT(2A)-receptor genes in hippocampus midbrain and TPH2 gene in midbrain in AKR.CBA-D13Mit76 mice compared with AKR mice were shown. Activation of nonspecific immunity by bacterial endotoxin lipopolysaccharide (LPS) administration did not affect the genes expression in AKR mice, but increased 5-HT(2A)-receptor expression in midbrain and decreased 5-HT(1A)-receptor expression in cortex in AKR.CBA-D13Mit76 mice. The results indicate: 1) the participation of gp130 in the regulation of TPH2, 5-HT(1A)- and 5-HT(2A)-receptor genes and 2) association of this protein in the genetically determined sensitivity to LPS.

Alterations in pharmacological and behavioural responses in recombinant mouse line with an increased predisposition to catalepsy: role of the 5-HT1A receptor.

BACKGROUND AND PURPOSE: One important syndrome of psychiatric disorders in humans is catalepsy. Here, we created mice with different predispositions to catalepsy and analysed their pharmacological and behavioural properties. EXPERIMENTAL APPROACH: Two mouse lines, B6-M76C and B6-M76B, were created by transfer of the main locus of catalepsy containing the 5-HT1A receptor gene to the C57BL/6 genetic background. Behaviour, brain morphology, expression of key components of the serotoninergic system, and pharmacological responses to acute and chronic stimulation of the 5-HT1A receptor were compared. KEY RESULTS: B6-M76B mice were not cataleptic, whereas 14% of B6-M76C mice demonstrated catalepsy and decreased depressive-like behaviour. Acute administration of the 5-HT1A receptor agonist 8-OH-DPAT resulted in dose-dependent hypothermia and in decreased locomotion in both lines. Chronic 8-OH-DPAT administration abolished the 5-HT1A receptor-mediated hypothermic response in B6-M76C mice and increased locomotor activity in B6-M76B mice. In addition, 5-HT metabolism was significantly reduced in the hippocampus of B6-M76C mice, and this effect was accompanied by an increased expression of the 5-HT1A receptor. CONCLUSIONS AND IMPLICATIONS: Our findings indicate that transfer of the main locus of hereditary catalepsy containing the 5-HT1A receptor from CBA mice to the C57BL/6 genetic background led to increased postsynaptic and decreased presynaptic functional responses of the 5-HT1A receptor. This characteristic establishes the B6-M76C line as an attractive model for the pharmacological screening of 5-HT1A receptor-related drugs specifically acting on either pre- or postsynaptic receptors. LINKED ARTICLES: This article is part of a themed section on Updating Neuropathology and Neuropharmacology of Monoaminergic Systems. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v173.13/issuetoc.

Risk neurogenes for long-term spaceflight: dopamine and serotonin brain system.

Mice were exposed to 1 month of spaceflight on Russian biosatellite BION-M1 to determine its effect on the expression of key genes in the brain dopamine (DA) and serotonin (5-HT) systems. Spaceflight decreased the expression of crucial genes involved in DA synthesis and degradation, as well as the D1 receptor. However, spaceflight failed to alter the expression of tryptophan hydroxylase-2, 5-HT transporter, 5-HT1A, and 5-HT3 receptor genes, though it reduced 5-HT2A receptor gene expression in the hypothalamus. We revealed risk DA and 5-HT neurogenes for long-term spaceflight for the first time, as well as microgravity-responsive genes (tyrosine hydroxylase, catechol-O-methyltransferase, and D1 receptor in the nigrostriatal system; D1 and 5-HT2A receptors in the hypothalamus; and monoamine oxidase A (MAO A) in the frontal cortex). Decreased genetic control of the DA system may contribute to the spaceflight-induced locomotor impairment and dyskinesia described for both humans and rats.

Effect of actual long-term spaceflight on BDNF, TrkB, p75, BAX and BCL-XL genes expression in mouse brain regions.

Mice of C57BL/6J strain were exposed to 1-month spaceflight on Russian biosatellite Bion-M1 to determine the effect of long-term actual spaceflight on the expression of genes involved in the processes of neurogenesis and apoptosis. Specifically, we focused on the genes encoding proapoptotic factor BAX, antiapoptotic factor BCL-XL, brain-derived neurotrophic factor (BDNF) and BDNF receptors TrkB and p75. Spaceflight reduced the expression of the antiapoptotic BCL-XL gene in the striatum and hypothalamus, but increased it in the hippocampus. To estimate environmental stress contribution into spaceflight effects we analyzed spaceflight-responsive genes in mice housed for 1 month on Earth in the same shuttle cabins that were used for spaceflight, and in mice of the laboratory control group. It was shown that 1-month shuttle cabin housing decreased BCL-XL gene expression in the striatum but failed to alter BCL-XL mRNA levels in the hippocampus or hypothalamus. Spaceflight failed to alter the expression of the proapoptotic BAX gene in all investigated brain structures, although the insignificant increase of the BAX mRNA level in the hippocampus of spaceflight mice was found. At the same time, shuttle cabin housing produced insignificant decrease in BAX gene expression in the hippocampus. In contrast to the BCL-XL gene, genes encoding BAX, BDNF as well as TrkB and p75 receptors did not respond to 30-day spaceflight. Thus, long-term spaceflight (1) did not affect the expression of genes encoding BDNF as well as TrkB and p75 receptors, (2) produced dysregulation in genetic control of the neuronal apoptosis, (3) implicated BCL-XL as the risk factor for spaceflight-induced behavioral abnormalities.

[Effects of stress on corticosterone level, expression of c-Fos gene and serotonin turnover in brain in mice with genetic predisposition to catalepsy].

Freezing or catalepsy is a passive-defensive reaction to stress. The participation of brain serotonin (5-HT) in the regulation of catalepsy was shown. The major gene of predisposition to catalepsy in CBA strain was localized in a 59-70 cM fragment of chromosome 13. This fragment was transferred from the CBA strain to genome of AKR non-cataleptic strain and created AKR. CBA-D13Mit76 (D13) congenic strain. The aim of the study was to compare the effects of acute stress (restriction, 1 h) on corticosterone level in plasma, the expression of c-Fos gene (neuromarker of stress) and serotonin metabolism in the brain in AKR catalepsy-resistant strain and congenic D13 catalepsy-prone strain. The level of corticosterone was significantly lower (p < 0.001) in the stressed D13 mice compared with the stressed AKR mice. Acute stress led to increased expression of c-Fos gene in the hypothalamus and midbrain in mice of both strains. Stress increased (p < 0.05) serotonin turnover in midbrain in D13 mice, but not in AKR. Thus, the fragment of chromosome 13, containing the major gene of catalepsy, participates in the regulation of hormonal response and serotonin turnover to acute stress.

Effect of brain-derived neurotrophic factor on behavior and key members of the brain serotonin system in genetically predisposed to behavioral disorders mouse strains.

The effect of brain-derived neurotrophic factor (BDNF) on depressive-like behavior and serotonin (5-HT) system in the brain of antidepressant sensitive cataleptics (ASC)/Icg mouse strain, characterized by depressive-like behavior, in comparison with the parental nondepressive CBA/Lac mouse strain was examined. Significant decrease of catalepsy and tail suspension test (TST) immobility was shown 17days after acute central BDNF administration (300ng i.c.v.) in ASC mice. In CBA mouse strain, BDNF moderately decreased catalepsy without any effect on TST immobility time. Significant difference between ASC and CBA mice in the effect of BDNF on 5-HT system was revealed. It was shown that central administration of BDNF led to increase of 5-HT(1A) receptor gene expression but not 5-HT(1A) functional activity in ASC mice. Increased tryptophan hydroxylase-2 (Tph-2) and 5-HT(2A) receptor genes expression accompanied by 5-HT(2A) receptor sensitization was shown in BDNF-treated ASC but not in CBA mouse strain, suggesting BDNF-induced increase of the brain 5-HT system functional activity and activation of neurogenesis in "depressive" ASC mice. There were no changes found in the 5-HT transporter mRNA level in BDNF-treated ASC and CBA mice. In conclusion, central administration of BDNF produced prolonged ameliorative effect on depressive-like behavior accompanied by increase of the Tph-2, 5-HT(1A) and 5-HT(2A) genes expression and 5-HT(2A) receptor functional activity in animal model of hereditary behavior disorders.