[Prospects for the use of drugs with anti-inflammatory properties for the treatment of depression]

The review briefly summarizes experimental and preclinical data of the role of pro-inflammatory cytokines in triggering pathophysiological changes associated with depression, primarily major depressive disorder (MDD), as well as the possibility of using anti-inflammatory drugs as antidepressants.

Chemogenetic Activation of Glutamatergic Neurons in the Juvenile Rat Cortex Reduces Anxiety

Abstract-Chemogenetic activation of glutamatergic neurons of the prefrontal cortex reduces the manifestations of psychoemotional anxiety during the juvenile period of ontogenesis. This result is the first evidence of feasibility of targeted chemogenetic control of neuronal activity during the early stages of brain development.

Doxycycline Used for Control of Transgene Expression has its Own Effects on Behaviors and Bcl-xL in the Rat Hippocampus

Doxycycline (Dox)-inducible transgenic approach is used to examine the neural mechanisms of anxiety and depression; however, its own effects on related behaviors are not clear. To address this, in the present study, we tested the anxiety- and depression-like behaviors in rats treated with Dox in drinking water (2 mg/ml) in the elevated plus-maze (EPM; on day 5) and forced swim (FST; on day 8) tests, respectively. In addition, the levels of mRNAs and proteins of brain-derived neurotrophic factor (BDNF) and anti-apoptotic protein Bcl-xL in the hippocampus (HIPP) and frontal cortex (FC) were also analyzed. Consumption of Dox for 4 days induced an anxiogenic-like phenotype that was manifested by the decreased percentages of open arm entries and time spent on the open arms of the EPM. After Dox for 7 days, animals demonstrated more active behavior in the FST than control rats as evidenced by the increase in climbing time. When assessed after the FST, expression of Bcl-xL was increased in the hippocampus of Dox-treated animals. Furthermore, hippocampal Bcl-xL content correlated positively with the duration of climbing in the test. This study is the first to find that Dox in treatment regime used to control transgene expression can affect anxiety- and depression-like behaviors in rats. Dox-induced increase in Bcl-xL expression in the hippocampus may be involved in the moderate activation of FST behavior.

[Anti-apoptotic protein enhances resilience to psychoemotional effects of stress]

Stress predisposes to depression by enhancing apoptosis and reducing neurogenesis in the brain. There are significant individual differences in resilience to the effects of stress on mood. These differences, at least in part, may be related to the expression of the anti-apoptotic protein Bcl-xL in the brain. Increased expression of this protein in the hippocampus may be an important factor of resilience to stress-induced depression. Expression of the Bcl-xL in the brainstem acquires the ability to respond to stress induction during the course of treatment with prozac concomitantly with the emergence of the therapeutic effect of this antidepressant on behavior. Processes linking stress and behavior in which the protein Bcl-xL is involved, are considered in this review.

Effects of swim stress and fluoxetine on 5-HT1A receptor gene expression and monoamine metabolism in the rat brain regions

Changes in gene expression of the brain serotonin (5-HT) 1A receptors may be important for the development and ameliorating depression, however identification of specific stimuli that activate or reduce the receptor transcriptional activity is far from complete. In the present study, the forced swim test (FST) exposure, the first stress session of which is already sufficient to induce behavioral despair in rats, significantly increased 5-HT1A receptor mRNA levels in the brainstem, frontal cortex, and hippocampus at 24 h. In the brainstem and frontal cortex, the elevation in the receptor gene expression after the second forced swim session was not affected following chronic administration of fluoxetine, while in the cortex, both control and FST values were significantly reduced in fluoxetine-treated rats. In contrast to untreated rats, no increase in hippocampal 5-HT1A receptor mRNA was observed in response to FST in rats chronically treated with fluoxetine. Metabolism of 5-HT (5-HIAA/5-HT) in the brainstem was significantly decreased by fluoxetine and further reduced by swim stress, showing a certain degree of independence of these changes on 5-HT1A receptor gene expression that was increased in this brain region only after the FST, but not after fluoxetine. FST exposure also decreased the brainstem dopamine metabolism, which was unexpectedly positively correlated with 5-HT1A receptor mRNA levels in the frontal cortex. Together, these data suggest that the effects of the forced swim stress as well as fluoxetine involve brain region-dependent alterations in 5-HT1A receptor gene transcription, some of which may be interrelated with concomitant changes in catecholamine metabolism.

[Behavior in the forced-swimming test and expression of BDNF and Bcl-xl genes in the rat brain]

A single exposure of rats to the forced-swimming stress decreased BDNF mRNA levels in the cortex and increased Bcl-xl gene expression in the hippocampus and amygdala 24 h after the stress. The animals demonstrated a depressive-like behavior and elevated blood corticosterone level. There was a significant negative correlation between BDNF mRNA level in the cortex and immobility time during swimming. Repeated exposure to swimming stress caused the elevation of the hippocampal BDNF mRNA level assessed 24 h after the second swimming session. The data suggest that stress-induced down-regulation of cortical BDNF gene expression and behavioral despair in the forced-swimming test may be interrelated. The increase in the BDNF and Bcl-xl mRNA levels may contribute to the mechanisms protecting the brain against negative effects of stress.

[Neurobiological mechanisms of depression and antidepressant therapy]

Depression represents a complex mental disorder which results from the contribution of multiple genetic and environmental factors. A depressive state can be characterized by abnormalities in the functions of monoaminergic neurotransmission, hypothalamic-pituitary-adrenocortical system, neurotrophins and cytokines in genetically predisposed individuals that endured the impact of stress or infection. Genetic, epigenetic and ontogenetic factors underlie these abnormalities. Manifestations of the pathology demonstrate associations with specific alleles of candidate genes. Epigenetic mechanisms of DNA methylation, acetylation and methylation of histones and processes of transcription and translation are also involved in the development of depressive symptoms and their amelioration under prolonged treatment with antidepressants. These processes are regulated by transcription factors and specific microRNAs. The search for effective means to affect activity of these intracellular targets with traditional pharmaceutical agents altering intercellular communication performed by neurotransmitters, hormones and tissue factors that provide long-lasting neuronal plasticity would be useful for unraveling the pathophysiological mechanisms of depression and for development of new approaches to its therapy.

[Neuroadaptive changes in brain during selective serotonin reuptake inhibitors action]

Selective serotonin reuptake inhibitors such as fluoxetine that are widely used for the treatment of depression and anxiety disorders produce neuroadaptive change not only in the serotoninergic system but also in other neuromediator systems. These changes may be involved in the therapeutic as well as in side effects of the drugs.

Up-regulation of tryptophan hydroxylase-2 mRNA in the rat brain by chronic fluoxetine treatment correlates with its antidepressant effect

Tryptophan hydroxylase-2 (TPH2), the rate-limiting enzyme in 5-HT synthesis in the brain, is a candidate for participation in a mechanism mediating the antidepressant effect of selective 5-HT reuptake inhibitors such as fluoxetine. Using real-time reverse transcription-polymerase chain reaction (RT-PCR) and semi-quantitative RT-PCR techniques, we have examined the effects of fluoxetine administration with drinking water (7.5 mg/kg/day) for 2, 4 and 8 weeks on TPH2 mRNA expression in the midbrain part of the dorsal raphe nucleus (DRN) and in the brainstem containing the rest of the raphe complex. Fluoxetine treatment for 4 and 8 weeks significantly increased basal TPH2 mRNA levels in the midbrain, an effect that was correlated with the appearance of antidepressant-like effects in the forced swim test. A significant induction of TPH2 and 5-HT transporter (5-HTT) mRNAs was detected in the midbrain of untreated rats 24 h after the swim test. In these animals, the swim test also produced a marked decrease in 5-HT metabolite (5-hydroxyindoleacetic acid (5-HIAA)) content in the amygdala. Fluoxetine treatment for 4 and 8, but not for 2 weeks, abolished these swim-induced changes in TPH2 and 5-HTT mRNAs levels in the midbrain and 5-HIAA content in the amygdala. The results of the present study suggest that TPH2 gene expression in the midbrain part of the DRN is implicated in depression and stress response, as well as in the antidepressant fluoxetine action.

[Involvement of striatal serotonin in fluoxetine effects on adrenocortical function and behaviour]

Treatment of the adult rats with selective serotonin (5-HT) reuptake inhibitor: fluoxetine and its complexes with glycyrrizhinic acid during 2 weeks (25 mg/kg/day) significantly increased plasma corticosterone levels that were measured after 5-min plus-maze. All the drugs decreased the content of 5-HT and its metabolite 5-hydroxyindoleacetic acid (5-HIAA) in the striatum as well as 5-HT in the hippocampus. There was a significant negative correlation between 5-HT in the striatum and corticosterone levels. These data suggest that fluoxetine induces serotoninergic changes in the striatum that might be related to neuroendocrine and behavioural effects of the drug.

Effect of repeated treatment with fluoxetine on tryptophan hydroxylase-2 gene expression in the rat brainstem

Selective serotonin (5-HT) reuptake inhibitors such as fluoxetine are widely used in the treatment of depression and anxiety; however, the mechanisms underlying their action and particularly the delay in therapeutic onset remain unclear. It is proposed that 5-HT reuptake inhibitors exert their therapeutic activity by increasing serotonergic neurotransmission; therefore, the aim of the present study was to investigate the effects of repeated treatment with fluoxetine (25 mg/kg/day p.o., 14 days) on expression of genes coding for proteins that involved in the synthesis and reuptake of 5-HT. Exposure of animals to plus-maze conditions on the first day of drug administration produced an increase in baseline anxiety on subsequent trial 2 weeks later. Fluoxetine strengthened the anxiogenic effects of maze experience. Two-week fluoxetine treatment also significantly reduced expression of tryptophan hydroxylase-2 (TPH2) and 5-HT transporter mRNAs as determined by RT-PCR in the brainstem. These changes were consistent with the decreased 5-HT levels and 5-HT turnover in the brain, and might contribute to the anxiogenic effects of the drug. The results also suggest that recently found association between treatment responses to fluoxetine and polymorphic variants of human TPH2 gene [Peters EJ, Slager SL, McGrath PJ, Knowles JA, Hamilton SP. Investigation of serotonin-related genes in antidepressant response. Mol Psychiatry 2004; 9:879-889] may be related to the drug effect on the TPH2 gene expression.

[Effects of fluoxetine on locomotor activity: possible involvement of dopamine]

Plus-maze benavior of adult mail rats was assessed and contents of 5-hydroxyindoleacetic acid (5-HIAA) and dopamine (DA) in different brain regions were analyzed after two-week fluoxetine treatment (25 mg/kg/day, per os). Chronic fluoxetine treatment produced a general decrease in the brain 5-HIAA content and a decrease in DA content in the frontal cortex and striatum. Behaviorally, fluoxetine-treated animals displayed enhanced anxiety and decreased locomotor activity. The DA depletion os supposed to be responsible for fluoxetine-produced hypolocomotion. This is supported by a significant correlation between the dopamine content in the frontal cortex and the number of entries into the closed arms of the plus-maze. The results suggest that the hypolocomotor effect of fluoxetine may involve the changes in the dopaminergic system.

The effects of fluoxetine and its complexes with glycerrhizic acid on behavior in rats and brain monoamine levels

The effects of the serotonin reuptake inhibitor fluoxetine (FL) and its complexes with glycyrrhizic acid (GA) in molar ratios of 1:1 (FLG-1) and 4:1 (FLG-4) on the behavior of adult rats were studied in an elevated cross maze, with measurement of brain monoamine and monamine metabolite levels. Agents were given via the intragastric route using a cannula at a dose of 25 mg/kg 1 h before testing. FL increased anxiety in the rats and decreased their movement activity; FLG-1 and FLG-4 had no effect on behavior. None of the agents affected brain serotonin content, though all decreased the levels of its metabolite 5-hydroxyindoleacetic acid in the hypothalamus, FLG-4 also decreasing this in the cortex. Noradrenaline levels in the hypothalamus were increased after FLG-1 and FLG-4. In the striatum, FL increased the levels of dopamine and its metabolite dihydroxyphenylacetic acid but had no effect on the level of transmitter catabolism. Unlike FL, FLG-1 activated dopamine metabolism in the striatum. Overall, use of FL complexed with GA significantly modified its behavioral effects, which appears to be associated with the effects of FL and its complexes on the function of the monoaminergic systems involved in controlling behavior.

Attenuation of alpha2A-adrenergic receptor expression in neonatal rat brain by RNA interference or antisense oligonucleotide reduced anxiety in adulthood

Brain alpha2-adrenergic receptors (alpha2-ARs) have been implicated in the regulation of anxiety, which is associated with stress. Environmental treatments during neonatal development could modulate the level of brain alpha2-AR expression and alter anxiety in adults, suggesting possible involvement of these receptors in early-life programming of anxiety state. The present study was undertaken to determine whether the reduction of the expression of A subtype of these receptors most abundant in the neonatal brain affects anxiety-related behavior in adulthood. We attenuated the expression of alpha2A-ARs during neonatal life by two different sequence specific approaches, antisense technology and RNA interference. Treatment of rats with the antisense oligodeoxynucleotide or short interfering RNA (siRNA) against alpha2A-ARs on the days 2-4 of their life, produced a marked acute decrease in the levels of both alpha2A-AR mRNA and [3H]RX821002 binding sites in the brainstem into which drugs were injected. The decrease of alpha2A-AR expression in the neonatal brainstem influenced the development of this receptor system in the brain regions as evidenced by the increased number of [3H]RX821002 binding sites in the hypothalamus of adult animals with both neonatal alpha2A-AR knockdown treatments; also in the frontal cortex of antisense-treated, and in the hippocampus of siRNA-treated adult rats. These adult animals also demonstrated a decreased anxiety in the elevated plus-maze as evidenced by an increased number of the open arm entries, greater proportion of time spent in the open arms, and more than a two-fold increase in the number of exploratory head dips. The results provide the first evidence that the reduction in the brain expression of a gene encoding for alpha2A-AR during neonatal life led to the long-term neurochemical and behavioral alterations. The data suggests that alterations in the expression of the receptor-specific gene during critical periods of brain development may be involved in early-life programming of anxiety-related behavior.

[Effects of fluoxetine and its complexes with glycyrrizhinic acid on behavior and brain monoamine levels in rats]

Effects of serotonin uptake inhibitor fluoxetine (F) and it's complexes with glycyrrizhinic acid (GA) in molar proportions 1GA : 1F (FGA-1) and 4GA : 1F (FGA-4) on rat behavior in elevated plus-maze and brain monoamine concentrations were studied. Drugs (25 mg/kg) were administered per os 1 h before investigations. F-treated rats showed increased anxiety and reduced locomotor activity, whereas FGA-1 and FGA-4 had no effects on the behaviors. None of the compounds modified brain tissue serotonin content, but all of them decreased the level of its metabolite 5-hydroxyindole-3-acetic acid level in the hypothalamus, and FGA-4 also decreased it in the cortex. Noradrenaline levels were increased in the hypothalamus of rats treated with F in both combinations with GA. In the striatum, F increased dopamine and its metabolite DOPAC levels, but their ratio (an indicator of the neurotransmitter turnover) was not altered by this drug. Unlike F, FGA-1 significantly activated dopamine turnover in the striatum. The data obtained suggested that application of F in complexes with GA significantly modified the drug behavioral effects and these alterations may be related to specific effects of the pure compound and its complexes on the functions of the brain monoaminergic systems that regulate investigated behavior.

[Cortical alpha-2a adrenoreceptors involved in the inhibitory control of motor activity in neonatal rats]

Involvement of alpha 2A-adrenoceptors in control of motor activity in neonatal rats was investigated using intrabrain injections of antisense deoxyoligonucleotide targeting mRNA of these receptors. Antisense-induced decrease in the receptor expression in the brain accompanied by an augmentation of animal's motor activity, which was evaluated as a number of paddling movements with the right forepaw. This antisense effect was stimulatory and was not related to somatic growth and maturation of reflexes in the animals. The antisensetreated pups differed from controls neither in body weight nor the latency of righting reflex. The data suggest that alpha 2A-adrenoceptors are involved in inhibitory control of motor activity of rat pups from the first day of life.

Effects of antisense oligodeoxynucleotide to the alpha2A-adrenoceptors on the plasma corticosterone level and on elevated plus-maze behavior in rats

Antisense strategy was used to investigate the role of alpha2A-adrenoceptor (alpha2A-AR) subtype in anxiety-related behavior. A 18-mer phosphorothioate oligodeoxynucleotide (AS-ODN) complementary to the alpha2A-AR mRNA was administered to the adult male rats for 3 days (1 nmol/5 microl/day) into the region of locus coeruleus (LC). Control groups received infusions of either oligodeoxynucleotide of a random sequence (RS-ODN) or saline. Treatment with AS-ODN significantly reduced the levels of alpha2A-AR mRNA in the brain stem. At the same time, AS-ODN treatment caused only a small reduction in [(3)H]clonidine binding (by 26-32%) in the brain stem which was not significant. Compared to both RS-ODN and saline controls, treatment with AS-ODN significantly increased the percentage of open arm entries in the elevated plus-maze while the total number of arm entries was unaltered. Also, AS-ODN treatment elevated basal levels of plasma corticosterone by 217% and 96% compared to both RS-ODN and saline controls. These changes in the hormone concentrations were at a level of marginal significance (p<0.1 versus random group). Taken together, the data indicate that administration of AS-ODN against alpha2A-ARs in the LC significantly reduced expression of alpha2A-AR mRNA in brain stem, moderately increased plasma corticosterone and had anxiolytic-like effect in the elevated plus-maze.

Effects of testosterone on alpha2A-adrenergic receptor expression in the rat brain

Androgens are involved in regulation of behaviour through intracellular mechanisms owing to their receptors. Involvement of intercellular messengers such as brain norepinephrine and adrenergic receptors (ARs) is seemed to be necessary to realise hormone-dependent behavioural effects. Castration of adult male rats, which decreases copulatory activity in the animals, was accompanied by a significant increase in 3H-clonidine (alpha2-AR agonist) binding site density in the frontal cortex. The levels of mRNA for the alpha2A-ARs (measured by RT-PCR) were increased in the brainstem of castrated males in parallel to the changes in cortical ARs densities. Testosterone treatment, that activates copulatory behaviour in castrates, down regulated alpha2A-AR mRNA levels in the brainstem and 3H-clonidine binding sites densities in the cortex, where terminals of the brain stem neurones are situated. Unlike in the brainstem, castration caused a decrease in alpha2A-AR mRNA in the cortex and testosterone up-regulated this mRNA in the cortical region. The data suggested that down-regulation of alpha2-ARs densities in the cortex that is induced by testosterone can be preferentially related to alpha2-ARs subpopulation which is expressed by the brainstem neurones and imported into the cortex by axons of these neurones.

[Subtype-specific clinically important effects of alpha 2-adrenergic receptors]

A- B- and C-subtypes of alpha 2-adrenoreceptors present in all mammals are involved in responses to currently existing subtype-nonselective ligands of these receptors widely used in medicine. Each of the subtypes has its own specific distribution in tissue and cells, onthogenetic pattern, specific regulation of activity and expression, and, as result, specific physiological functions. The latter suggests opportunities of using the subtype-specific for correction of the functions depending on this receptor. The article reviews the role of individual subtypes of alpha 2-adrenoreceptors in regulation of neurochemical transmission of cardiovascular system, psychoemotional state and development of psychic disorders, and also male sexual behaviour.

Effects of antisense to the (alpha)2A-adrenoceptors administered into the region of the locus ceruleus on behaviors in plus-maze and sexual behavior tests in sham-operated and castrated male rats

Clinical and experimental findings have implicated brain alpha2-adrenoceptors in the regulation of many physiological functions, including sexual activity and stress-related behavior. However, which subtypes of the three alpha2-adrenoceptors that have now been cloned (alpha2A, alpha2B, and alpha2C) are involved in these controls have yet to be established. Here, we investigated the contribution of alpha2A-adrenoceptors of the locus ceruleus, the principal source of brain noradrenaline, to exploratory and sexual behaviors. Using administration of antisense oligodeoxynucleotide to inhibit the receptor expression, we found that reductions in brainstem alpha2A-adrenoceptor mRNA levels and alpha2-adrenoceptor densities induced by antisense treatment were not accompanied by any changes in the major characteristics of male sexual activity, such as mount latencies and numbers of mounts. However, in sexual behavior tests, antisense-treated male rats had decreased numbers of rearings and thus have higher percentages of behaviors positively correlated with sexual activity. Besides, antisense-treated animals had decreased anxiety in plus-maze tests. The data demonstrate that inhibition of alpha2A-adrenoceptor expression in the region of the locus ceruleus has an anxiolytic-like effect and facilitates male's attention to female in sexual behavior test.

[Analysis of the functional role in behavior of the neuromediator receptor by antisense knockdown of its gene expression]

Now available nucleotide sequences of neurotransmitter receptor genes enable to apply oligonucleotides targeted to mRNAs of these genes for highly selective inactivation of their expression (antisense-knockdown) and for function determination of single receptor subtype by this experimental approach. The antisense-knockdown may be of special importance in case of receptor families members of which are pharmacologically similar. Advantages of the antisense technology for investigation into the brain neurotransmitter receptor function in regulation of behaviour, are discussed.

Genetic differences in the synthesis and reception of noradrenaline in the mouse brain and behavior in a novel environment

The activity of tyrosine hydroxylase, the key enzyme in catecholamine biosynthesis, was studied along with adrenoceptor density in the brains of male CBA/Lac, BALB/cLac, and C57BL/6J mice, which show different responses to novel environments. C57BL mice showed the highest level of movement activity and the lowest level of emotionality in a novel environment. Mice of this line also showed the highest brainstem tyrosine hydroxylase activity. At the same time, the density of beta-adrenoceptors in the cortex and hypothalamus of C57BL mice was lower than in the other two lines of mice, while the density of alpha2-adrenoceptors in these parts of the brain was lower than in CBA mice. In BALB mice, movement activity was twice as high as in CBA mice, while levels of emotionality were similar in these two lines. Tyrosine hydroxylase activity was higher in the cerebral cortex of BALB mice, while the density of alpha2-adrenoceptors was lower than in CBA mice. These results show that increased investigative activity and decreased emotionality were seen in animals with higher levels of noradrenaline synthesis and decreased density of adrenergic receptors in the brain.

Role of the serotoninergic system in the acceleration of sexual maturation in wild Norway rats selected for reduced aggressiveness toward humans

The role of the serotoninergic system in acceleration of the sexual development of domesticated rats (Rattus norvegicus) was assessed. The onset of age-related changes in hypothalamic serotonin during prepubertal period occurred earlier in domesticated than in aggressive male rats. Blockade of the serotoninergic system after p-chlorophenylalanine (PCPA) administration on days 40 and 44 delayed the development of the reproductive system in both aggressive and domesticated males. In 60-day-old rats treated with PCPA, levels of testosterone in plasma and the number of mature spermatozoa in epididymis were decreased compared to controls. At the same time, the administration of PCPA on days 30 and 34 did not modify basal testosterone secretion and other parameters in 60-day-old aggressive rats and produced a decrease similar to PCPA injections on days 40 and 44, although less pronounced, in the weights of testes in domesticated animals. Administration of 5-hydroxytryptophan (5-HTP), a precursor of serotonin synthesis, on days 30, 32, 34, 36 and 38 increased plasma testosterone levels and weights of the sex organs in 60-day-old domesticated males, but did not significantly affect the development of reproductive system in aggressive animals. These data indicate that serotonin stimulates sexual development of males during prepubertal period and this activating effect of serotonin occurs earlier in domesticated than in aggressive males. They also suggest that the acceleration in sexual maturation of domesticated rats could result from changes in the ontogenetic dynamic of hypothalamic serotonin induced by a selection for low aggressiveness towards man.

[The ontogenetic correlations of noradrenaline level and adrenergic receptor density in the rat brain]

We studied the level of noradrenaline and the density of alpha 2- and beta-adrenoreceptors in the brain stem and cerebral cortex of 12-day- and 21-day-old rat fetuses, as well as of rats at the ages of 1, 2, 5, 7, 9, 16, 21, 35, and 70 days. We found a positive correlation between the level of noradrenaline in the brain stem and the density of beta-receptors in the cerebral cortex, and between the amount of alpha 2- and beta receptors in the cerebral cortex, as well as between the values of each of these indices of the neurochemical system and body weight. Significant negative correlations (r = -0.72 and r = -0.88, respectively) were found between the amount of alpha 2-adreno-receptors in the brain stem and the content of noradrenaline in this brain region, as well as in the cerebral cortex. Explanations of these positive and negative correlations between the level of noradrenaline and the amount of adrenergic receptors in the rat brain during ontogenesis are discussed.

[Genes, hormones and the risk factors in the development of the male phenotype]

The onset of the expression of Sry and other sex-determining genes such as SF-1, DAX-1, WT-1 and SOX family initiates the testis organogenesis from the bipotential primordium. The fetal testis produces anti-Mullerian hormone and testosterone. These two hormones play essential role in the further development of the male phenotype. The bases for the activity of the sexual function and behavior are created within frames of these processes. Interindividual differences in these characters may achieve high degrees. Alleles of the sex-determining genes and the genes of the other genetic systems which participate in regulation of reproduction may be responsible for this variability. For example, the inherited variations in testosterone levels in the blood are negatively correlated to the alpha2-adrenergic receptor densities in the hypothalamus in males of mouse strains. Testosterone level in the fetal blood during critical period of sexual differentiation is one of the key points through which genetic and ontogenetic factors affect male sexual development. We have found nearly twofold interstrain differences in testosterone levels in the blood of male rat fetuses of 2 strains. The rats with higher testosterone levels during intrauterine development have higher rates of sexual maturation and sexual activity in future life. Genetic differences were also found in sensitivity of fetal testosterone to disruptive influences. These differences may be the reason for the strain-specific effects of prenatal stress or glucocorticoid treatment on the male sexual development in rats and mice. Substances and treatments which are capable of changing testosterone levels and/or interaction of these hormones with their receptors: ionizing radiation, pesticides, xenoestrogenes, drugs, alcohol, various stressors are the risk factors of the male sexual development.

[The behavioral effects of a single adverse exposure in a number of rat generations: the role of maternal glucocorticoids]

The ionizing irradiation of rat fetuses during the last third of intrauterine development increased blood corticosterone level adulthood and decreased the open field locomotion of their adult offsprings of the next first nonirradiated generation. Treatment of the pregnant rats with glucocorticoids also decreased the offspring locomotion. Irradiation of fetuses in the middle of embryogenesis decreased blood corticosterone level in adulthood and shortened the open-field freezing reaction of their adult offsprings of the next first nonirradiated generation. Adrenalectomy of females before mating decreasing the blood corticosterone level had a similar effect on freezing duration of their adult offsprings. Irradiation of the ancestors within the last third of their intrauterine development had no effect on blood corticosterone level of their adult offsprings of the first generation and produced no behavioral alterations in their descendants of the next second nonirradiated generation. Irradiation of the ancestors in the middle of their embryogenesis decreased the stress-induced corticosterone response in their adult offsprings of the first generation and increased rearings and locomotion in their descendants of the next second nonirradiated generation. The data suggest that a single noxious treatment may have behavioral effects throughout two consequent generations of rats. Mother's glucocorticoid hormones may be one of the factors which transmit the effect.

[Genetic variations of noradrenaline synthesis and reception in the mouse brain and the animal behavior in the new environment]

C57BL mice were found to have the highest locomotion and the lowest emotionality under novel environment out of three strains of mice. Their brain stem TH activity was increased whereas the density of alpha2-ARs and beta-ARs were decreased in their cortex and hypothalamus. The BALB mice were twice as virulent as the CBA mice whereas the emotionality was the same in both strains. In general, low emotionality and high locomotion in novel environment were found in mice with increased activity of norepinephrine synthesis and decreased amount of adrenergic receptors in the brain.

[Regulation of expression of adrenergic receptors by steroid hormones]

Steroid hormones regulate density of adrenergic receptors in peripheral tissues and in the brain. The hormones affect transcription of the adrenergic receptors genes, the receptor protein synthesis and modifications. Steroid-induced changes in adrenergic receptors densities may be an important link for the effects of steroid hormones on hormone-dependent functions and behaviour.

Brain catecholamines and the hypothalamo-hypophyseal-adrenocortical system in inherited arterial hypertension

Rats with inherited stress-induced arterial hypertension (NISAG rats) and normotensive Wistar rats were used for studies of age-related changes in arterial pressure (BP), in the activity of the hypothalamo-hypophyseal-adrenocortical system (HHAS), and noradrenaline levels in brain structures involved in regulating these functions, with the aim of identifying possible relationships between them. It is suggested that the noradrenaline deficiency seen at the age of four weeks in the hypothalamus and medulla oblongata in NISAG rats is involved in the pathogenesis of hypertension and in disturbing the function of the HHAS. Transient increases in brain catecholamine synthesis in the fourth week of life lead to prolonged reductions in BP and complete recovery of HHAS responses to stress in adult animals. Correction of BP and HHAS function is accompanied by changes towards the normal in noradrenaline levels in the hypothalamus and medulla oblongata and in the numbers of alpha 1-adrenoceptors in the medulla oblongata.

[The role of glucocorticoids at the corticosterone level after stress in the early ontogeny of gray rats]

Norway rats were subjected to stress procedure of saline or hydrocortisone injections. The saline-treated rats revealed an increased level of the plasma corticosterone as opposed to hydrocortisone-treated ones. The modification of adrenocortical function with the stress in early postnatal life seems to be connected with changes in hypothalamic catecholamine synthesis and can be prevented with exogenous glycocorticoids.

[Corticosterone and testosterone in the blood of adult rats: the effects of low doses and the times of the action of ionizing radiation during intrauterine development]

Corticosterone levels in the blood and adrenal weights in adult rat males were increased after low-dose gamma irradiation during the last third of their intrauterine development; an increase of the dose decreased them. Decrease in testosterone levels and testis weights were dose-dependent. External and internal irradiation of females on the 11-14 days of pregnancy inhibited adrenals and increased testosterone levels and seminal vesicles weights in offspring. The changes of hormonal balance in adult animals depend on dose and period of ionizing irradiation during intrauterine development.

[Sexual behavior and alpha-2 adrenoreceptors in the neocortex of male rats after castration and testosterone administration]

Castration of male rats inhibited their sexual behaviour and increased the density of the alpha-2 adrenergic receptors in the brain cortex. Treatment of castrated or intact males with testosterone activated their sexual behaviour and decreased the receptor density in the brain cortex. The obtained evidence testify to the involvement of the brain alpha-2 adrenergic receptors in the effect of testosterone on male sexual behaviour.

[Brain catecholamines and the hypothalamo-hypophyseal-adrenocortical system in hereditary arterial hypertension]

Central catecholaminergic mechanisms regulating hypothalamic-pituitary-adrenocortical system (HPAS) and arterial blood pressure (ABP) are closely related. In adult rats with inherited stress-induced arterial hypertension (ISIAH rats), response of the HPAS to emotional stress is diminished. At the same time, the level and metabolic rate of noradrenaline (NA) in many brain regions taking part in the HPAS and ABP control are decreased, and the number of alpha 1-adrenoceptors in the medulla is elevated. Age-dependent changes and interstrain differences in basal and stress-induced plasma corticosterone levels and brain noradrenaline were studied at the age from 2 up to 18 weeks in ISIAH rats and normotensive Wistar rats. It was found that the 4th week of life in the ISIAH rats is a critical period in the development of inherited hypertension. At this time, fast forming of the hypertension is accompanied by an increase in adrenocortical stress responsivity and a fall in the medulla and hypothalamic NA contents. A short-term augmentation of the brain NA synthesis on the 4th week by L-DOPA and carbidopa treatment in the ISIAH rats was followed by a normalization of the arterial pressure and pituitary-adrenocortical function in adult animals accompanied by restoration of hypothalamic and medulla NA levels and medulla alpha 1-adrenoceptor number.

[Genetic and ontogenetic variability in the noradrenergic regulation of adrenocortical function]

Corticosterone levels in the blood under restriction positively correlated with the hormone response to i.c.v. norepinephrine injection in 7 genetic groups of rats. Reactions to stress and norepinephrine simultaneously decreased in adult rats after prenatal glucocorticoid treatment. Prenatal stress or corticosterone treatment have a lasting effect on typosine hydroxylase (TH) activity and adrenoligands binding in the mice brain. Prenatal treatment increased TH activity in the noradrenergic system of the brain and decreased binding of radiolabelled prazosin, clonidine and dihydroalprenolol in some brain regions as well as stress reaction in mice. Thus, individual variations in adrenocortical stress response may be related to the differences in the function of the brain noradrenergic system.

[The brain catecholaminergic system during the long-term correction of hereditary arterial hypertension]

L-DOPA administration to 21--25-day-old rats with inherited stress-induced arterial hypertension (ISIAH rats)lowered arterial pressure both at rest and in emotional stress in adult rats. The effect seems to be due to enhancement of the brain catecholamine synthesis rather than the peripheral one in early ontogenesis. The long-term hypotensive effect of the L-DOPA was supposed to be caused in part by changes revealed in the brain catecholaminergic system.