Bridging the mood and stress hormone levels between mothers and their babies: The study design and first preliminary results

The neurobiological mechanisms involved in the influence of post-partum maternal mood fluctuations on child development are far from being understood. Here we present the design of an ongoing study aimed to test the hypothesis that the mental state of the mother has an impact on her neonate which is manifested by similarities in the neuroendocrine function of the mother and the child. The hypothesis is being tested under both stress and non-stress conditions in mothers and babies aged 3-4 days and 7-9 months. The focus will be given to correlations with maternal postpartum mood. To confirm the correctness of methodological approaches and the feasibility of the study several preliminary analyses were performed. Salivary alpha-amylase activity as a marker of sympathetic activation and cortisol as the effective hormone of the hypothalamic-pituitary-adrenocortical axis were measured. The obtained results showed the feasibility of saliva sampling in neonates using a sampling time of 120 s. The analysis of cortisol in hair revealed increased concentrations during the third trimester of pregnancy, which is consistent with the knowledge of high cortisol concentrations during pregnancy. A positive correlation was observed between salivary cortisol values before and after the stress test in mother-infant dyads at both the post-partum period and 7-9 months thereafter. Understanding the mechanisms involved in "the bridge" between the mother and her baby will help to develop necessary interventions directed to help mothers in the early postpartum period.

Altered responsiveness to glutamatergic modulation by MK-801 and to repeated stress of immune challenge in female dopamine transporter knockout rats

Chronic stress is a key factor in psychiatric and neurological disorders often worsening disease symptoms. In this study, a unique animal model, the dopamine transporter knockout (DAT-KO) rat exhibiting behavioral signs resembling those occurring in mania, schizophrenia, attention deficit hyperactivity disorder, and obsessive-compulsive disorder was used. We have tested the hypothesis that the hyperdopaminergic state in DAT-KO rats (i) modulates behavioral response to the NMDA antagonist MK-801 (dizocilpine) and (ii) leads to abnormal endocrine and immune activation under subchronic stress induced by an immune challenge. Glutamatergic modulation with MK-801 induced a different behavioral pattern. While the WT rats responded to MK-801 injection with a robust rise in their locomotor activity, the hyperactive DAT-KO rats exhibited reduced locomotion. Signs of chronic stress including increased basal corticosterone and aldosterone but blunted anxiety were demonstrated in rats lacking the DAT. Repeated injections of increasing doses of lipopolysaccharide (LPS, 5 days) did not modify plasma prolactin concentrations which were however significantly lower in DAT-KO than in WT rats. Concentrations of plasma high mobility group box 1 (HMGB1) protein were significantly higher in LPS-treated DAT-KO than in WT rats. The gene expression of interleukin-6 in the anterior pituitary increased under the stress induced by the immune challenge in the WT but not the DAT-KO rats. The most evident differences between the genotypes were revealed in the spleen. The splenic gene expression of interleukin-1β, interleukin-6, and HMGB1 was lower and that of ferritin was higher in DAT-KO compared to WT rats. Obtained results emphasize the functional interaction of the endocrine and immune systems with monoamine and glutamatergic neurotransmission in the mechanisms leading to behavioral alterations and psychiatric disorders associated with dopamine dysfunction.

Role of miR-124-3p in regulatory mechanisms of Gpm6a expression in the hippocampus of chronically stressed rats

The neuronal membrane glycoprotein M6a (GPM6A) belongs to the family of myelin proteolipid protein and plays a role in neuronal remodeling and plasticity. Decreased expression of GPM6A mRNA is observed in the hippocampal tissue of suicide victims who suffered from depression and after chronic stress exposure in animals. The regulatory mechanisms that impact expression of GPM6A under chronic stress or in pathological conditions are not well understood. Previously, miRNAs miR-133b, miR-124-3p, and miR-9-5p have been shown to regulate expression of Gpm6a mRNA under normal conditions. Here, we employed the paradigm of chronic restraint stress in rats and using quantitative polymerase chain reaction (qPCR) showed downregulation of expression of Gpm6a and the brain-derived neurotrophic factor (Bdnf) genes at mRNA level as well as miR-133b, miR-124-3p, but not miR-9-5p in the hippocampus of chronically stressed rats. Furthermore, we observed alterations in the expression of histone deacetylase (Hdac5) and myocyte enhancer factor 2C (Mef2c) mRNAs. Our data suggest that chronic stress influences Gpm6a expression by miR-124 mediated impact on the expression of Hdac5 and Mef2c. Upon miR-124 overexpression in hippocampal neurons cultured in vitro we observed enhanced neuronal arborization as evaluated by Sholl analysis, increased Gpm6a and Mef2c expression, and decreased Hdac5 expression. Moreover, treatment of hippocampal neurons cultured in vitro with BDNF resulted in an elevation in the miR-124-3p expression, a decrease in the miR-9-5p expression but did not affect miR-133b. This was accompanied by augmented expression of Gpm6a and Mef2c mRNAs and significantly lower levels of Hdac5 mRNA. Altogether, these results indicate that the regulatory mechanism that influence expression of Gpm6a under chronic stress involves miR-124 mediated impact on the expression of Hdac5 and Mef2c and a role of BDNF in the activation of Gpm6a expression.

Association of HTTLPR, BDNF, and FTO Genetic Variants with Completed Suicide in Slovakia

Since suicide and suicidal behavior are considered highly heritable phenotypes, the identification of genetic markers that can predict suicide risk is a clinically important topic. Several genes studied for possible associations between genetic polymorphisms and suicidal behaviors had mostly inconsistent and contradictory findings. The aim of this case-control study was to evaluate the associations between completed suicide and polymorphisms in genes BDNF (rs6265, rs962369), SLC6A4 (5-HTTLPR), and FTO (rs9939609) in relation to sex and BMI. We genotyped 119 completed suicide victims and 137 control subjects that were age, sex, and ethnicity matched. A significant association with completed suicide was found for BDNF rs962369. This variant could play a role in completed suicide, as individuals with the CC genotype were more often found among suicides than in control subjects. After sex stratification, the association remained significant only in males. A nominally significant association between the gene variant and BMI was observed for BDNF rs962369 under the overdominant model. Heterozygotes with the TC genotype showed a lower average BMI than homozygotes with TT or CC genotypes. FTO polymorphism (rs9939609) did not affect BMI in the group of Slovak suicide completers, but our findings follow an inverse association between BMI and completed suicide.

Testosterone but not cortisol concentrations in hair correlate between mothers and their prepubertal children under real-life stress conditions

The aim of the present study is to test the hypothesis that there is an association between the neuroendocrine state, reflected by testosterone and cortisol concentrations in hair, of the mother and her child under difficult real-life stress conditions (COVID-19 pandemic). The research sample consisted of 45 healthy mothers and their prepubertal children (7 - 11 years) of both sexes. The hair samples of mother-child dyads were collected twice to obtain cumulative stress hormone concentrations from April till the end of June and July till the end of September 2020. Thus, 90 mother-child pairs were analyzed. The results showed that both cortisol and testosterone concentrations were significantly higher in the hair of mothers compared to those in their children. The results of cortisol concentrations in hair do not support the hypothesis stated above. In line with our hypothesis are the results of hair testosterone measurements showing a positive correlation between testosterone concentrations in mothers and their children. With respect to the known relationship of testosterone with aggressive behavior, an important finding is that above-mentioned correlation was particularly strong in women with intense subjective feelings of anger in the investigated three months period. Women with strongly prevalent subjective feelings of sadness failed to show a significant correlation between hair cortisol concentrations in mothers and their children, in spite of the known relationship of cortisol to depressive mood. It may be suggested that chronic testosterone secretion reflects the association between the neuroendocrine function of the mother and her child under real-life stress conditions.

Analysis of Motives and Factors Connected to Suicidal Behavior in Patients Hospitalized in a Psychiatric Department

(1) Background: This study aimed to investigate the motives and factors connected to suicidal behavior in 121 hospitalized patients with intentional self-harm (diagnosis X 60-81 according to the ICD-10); (2) Methods: Suicidal behavior of the patient was assessed from data obtained by psychiatric examinations and by the Columbia Suicide Severity Rating Scale. Analysis of data to identify the patients’ reason and motives behind suicidal behavior in a group of patients with a suicide attempt (SA, n = 80) and patients with Non-Suicidal Self-Injurious Behavior (NSSIB, n = 41) was carried out; (3) Results: Results showed that patients with affective disorder have a 19-times higher rate of SA against other diagnoses. Patients with personality disorders have a 32-times higher rate of NSSIB than patients with other diagnoses. Living alone and the absence of social support increased the likelihood of SA. Qualitative data analysis of patients’ statements showed different themes in the justification of motives for suicidal behavior between SA and NSSIB cases. Significant differences were shown for non-communicated reasons, loneliness, social problems, extortion, and distress; (4) Conclusions: The evaluation of patients’ verbal statements by qualitative analysis during the psychiatric examination should be considered in clinical practice. It should be considered to include self-poisoning in the criteria of the Non-suicidal Self-Injury diagnostic categories.

Psychotropic Drug Effects on Steroid Stress Hormone Release and Possible Mechanisms Involved

There is no doubt that chronic stress accompanied by adrenocortical stress hormone release affects the development and treatment outcome of several mental disorders. Less attention has been paid to the effects of psychotropic drugs on adrenocortical steroids, particularly in clinical studies. This review focuses on the knowledge related to the possible modulation of cortisol and aldosterone secretion under non-stress and stress conditions by antipsychotic drugs, which are being used in the treatment of several psychotic and affective disorders. The molecular mechanisms by which antipsychotic drugs may influence steroid stress hormones include the modulation of central and/or adrenocortical dopamine and serotonin receptors, modulation of inflammatory cytokines, influence on regulatory mechanisms in the central part of the hypothalamic-pituitary axis, inhibition of corticotropin-releasing hormone gene promoters, influencing glucocorticoid receptor-mediated gene transcription, indirect effects via prolactin release, alteration of signaling pathways of glucocorticoid and mineralocorticoid actions. Clinical studies performed in healthy subjects, patients with psychosis, and patients with bipolar disorder suggest that single and repeated antipsychotic treatments either reduce cortisol concentrations or do not affect its secretion. A single and potentially long-term treatment with dopamine receptor antagonists, including antipsychotics, has a stimulatory action on aldosterone release.

Steroid stress hormone changes throughout the menstrual cycle: A rise in evening aldosterone concentration in early luteal phase precedes the symptoms of premenstrual syndrome

There is still a lack of consistent evidence on dysregulation of steroid stress hormones cortisol and aldosterone in premenstrual syndrome (PMS). We aimed to test the hypothesis that, in healthy women, salivary aldosterone concentrations are higher in those with PMS compared to controls, particularly during the luteal phase of the menstrual cycle. In total, 99 female subjects (49 women with and 50 women without PMS) participated in a prospective non-interventional case-control study. Saliva sampling was performed in the follicular (day 8), early luteal (day 20) and late luteal phase (2 days before expected onset of bleeding) of the menstrual cycle in the morning and the evening. The results confirmed the hypothesis that salivary aldosterone concentrations are higher in women with PMS during the early luteal phase compared to controls (p < .01) in the evening. Early luteal phase aldosterone concentrations positively correlated with the frequency of premenstrual symptoms. Women with PMS exhibited a flatter morning to evening aldosterone slope compared to controls (p < .05). Morning and evening salivary cortisol concentrations were unchanged throughout the menstrual cycle in both groups of women. In conclusion, evening salivary aldosterone, but not cortisol concentrations, are increased in women with PMS during the early luteal phase compared to controls. Cortisol does not appear to be involved in the mechanisms contributing to the course of PMS. High evening salivary aldosterone in the early luteal phase may represent an important risk factor and could be of predictive value for the occurrence of premenstrual symptoms.

Tight junction proteins in the small intestine and prefrontal cortex of female rats exposed to stress of chronic isolation starting early in life

BACKGROUND

Simultaneous evaluation of barrier protein expression in the gut and the brain and their modulation under stress conditions have not been studied before now. As the permeability and function of the gut and blood-brain barrier are different and both express the MRs, we hypothesized that stress of post-weaning social isolation induces changes in tight junction protein expression in the gut which are (1) independent of changes in the brain and (2) are mediated via the mineralocorticoid receptor (MR).

METHODS

First, using UPLC-MS/MS we have successfully validated and selected a dose (1.2 mg/rat/day) of the MR antagonist spironolactone to treat female rats exposed to stress of chronic isolation or control conditions from postnatal day 21 for 9 weeks.

KEY RESULTS

Isolation stress caused an enhancement of gene expression of occludin and ZO-1 and a decrease in claudin-5 and MR expression in both the small intestine and prefrontal cortex. Isolation stress failed to decrease claudin-5 (small intestine) and MR (prefrontal cortex) gene expression in spironolactone-treated rats. MR blockade resulted in a decrease in claudin-15 expression in the small intestine. Anxiogenic effect of chronic stress, measured in elevated plus-maze test, was partly prevented by spironolactone treatment.

CONCLUSIONS & INFERENCES

Claudins, the main regulators of intestinal barrier permeability responded to chronic stress of social isolation and/or simultaneous blockade of MR in female rats by alterations independent of changes in the brain cortex. The results suggest a physiological role of MR in the control of claudin expression in the small intestine, but not in the brain cortex.

Relationships between antenatal corticosteroids and catecholamine blood pressure support in neonates: considering of maternal stress-related diseases

Healthy child development is under the influence of prenatal and perinatal exposure to stress stimuli. The aim of this study is to test the hypotheses that (1) neonates requiring catecholamine blood pressure support are more often born to mothers with stress-related cardiometabolic diseases, (2) maternal stress-related diseases are associated with more frequent requirement of maternal corticosteroid treatment and (3) antenatal steroid exposure of neonates reduces the need of postnatal catecholamine support. A retrospective cohort study was performed on a sample of 427 mature (13%), preterm (64%) and extremely preterm (23%) neonates of both sexes. Mothers at risk of preterm delivery were treated with dexamethasone. The blood pressure support in neonates was performed by intravenous treatment via umbilical or epicutaneous venous catheter with dopamine (5 ug/kg/min) or dobutamine (5 ug/kg/min) or a combination of both. The results showed a lack of association between maternal stress-related diseases and the complicated outcome of their neonates. Maternal treatment with corticosteroid dexamethasone was associated with lower frequency of catecholamine blood pressure support requirement. Catecholamine support was more needed in male infants. Thus, the occurrence of maternal cardiometabolic stress-related diseases does not appear to be related to the need of catecholamine support in the neonate. In agreement with the second hypothesis, a more frequent maternal corticosteroid treatment was associated with the presence of maternal stress-related diseases. Most importantly, the obtained results support the hypothesis on positive influence of maternal glucocorticoid administration on cardiovascular outcome of the neonate, representing an additional beneficial effect of antenatal corticosteroids. LAY SUMMARY Maternal hypertension, diabetes and obesity, which belong to cardiometabolic stress-related diseases, failed to show a negative influence on neonatal health as was determined by the need of catecholamine blood pressure support in a large sample of 427 immature and mature newborns. Since glucocorticoids are often viewed as negative agents that should be avoided, the important finding of the present study is the beneficial effect of maternal corticosteroid treatment on blood pressure stability of the neonate.

Lower activity of salivary alpha-amylase in youths with depression

Measurement of basal and stress-induced salivary alpha-amylase activity may help to understand autonomic nervous system disturbance in mental disorders. The potential sympathetic nervous system dysregulation in children and adolescent psychopathologies is mostly unknown. The present study was aimed to test the hypothesis that salivary alpha-amylase activity is higher in youths diagnosed with depression than in healthy subjects considering a part of the daily rhythm of enzyme activity and its morning to midday slope. A total of 30 children aged 15 ± 0.46 years (15 patients with depression, 4 boys, 11 girls, and 15 sex- and age-matched healthy controls) participated in the study. Two saliva samples were collected from each subject to measure activity of alpha-amylase in the morning and midday. The results of the present study revealed that the midday but not morning alpha-amylase activity was lower in patients with depression than in healthy controls. The diurnal increase in enzyme activity present in healthy subjects was absent in patients. The children and adolescents with depression exhibited flatter morning to midday slopes of alpha-amylase activity. In conclusion, the present results indicate a disturbance of alpha-amylase daily rhythm in youths with depression and motivate further studies on the relationship between sympathetic activation and mood disorders.

Dopamine concentrations and dopamine receptor gene expression in emotion-related brain structures of female adult rats exposed to stress of chronic isolation from weaning

It is known that early-life stress events induce profound consequences on emotional brain regions including amygdala, involved in emotional processing and the ventral tegmental area (VTA), which contains neuron cell bodies of the mesolimbic dopaminergic system. The aim of this study is to test the hypothesis that stress induced by long-term social isolation from weaning in female rats is associated with alterations in amygdalar dopamine receptor gene expression and VTA dopamine concentrations. Rats were weaned on postnatal day 21 and then exposed to stress of chronic isolation for 9 weeks. Control animals were housed socially. Amygdalar dopamine D1 but not D2 receptor gene expression was decreased in isolated rats compared to controls. Dopamine concentrations in the VTA were enhanced following chronic isolation. A negative correlation was observed between amygdalar D1 gene expression and dopamine concentrations in the VTA. In conclusion, a reduction of dopamine D1 receptor gene expression in the amygdala in response to stress induced by chronic isolation in female rats was accompanied by an increase in dopamine concentration in the VTA. Further studies are needed to understand the physiological significance, if any, of negative association of amygdalar dopamine receptor D1 gene expression and dopamine concentrations in the VTA.

Classical Steroids in a New Fashion: Focus on Testosterone and Aldosterone

Several endocrine glands produce steroid hormones. Thanks to the work of chemists and biochemists, the main synthetic as well as metabolic pathways of steroid hormones were included in the textbooks more than 50 years ago and the classical endocrine gland functions were identified. Later on, evidence of steroid hormone effects beyond the classical endocrine gland function has been accumulating. Testosterone was shown to participate in the stress response and may influence coping with stressors. We have shown a decrease in testosterone concentrations in saliva in children undergoing a school exam compared to values on a non-exam school day. Testosterone has been associated with different cognitive functions in both adults and children. Circulating testosterone has been linked to negative symptoms of schizophrenia. Aldosterone is acting via mineralocorticoid receptors, which are thought to be fully occupied by glucocorticoids in the brain. Until now, an action of aldosterone in the brain has not been considered at all, because the enzyme 11-beta-hydroxysteroid dehydrogenase type 2, which would enable aldosterone to bind to receptors is absent in most of the brain areas. We have brought evidence that aldosterone can act in the brain and produce anxiogenic and depressogenic effects. To facilitate the translation of animal findings into clinical research, we have developed methodology for measurement of salivary aldosterone and obtained first data on a relationship between salivary aldosterone and trait anxiety. We have shown that salivary aldosterone concentrations reflect treatment outcome in patients with major depressive disorder.

Salivary Aldosterone, Cortisol, and Their Morning to Evening Slopes in Patients with Depressive Disorder and Healthy Subjects: Acute Episode and Follow-Up 6 Months after Reaching Remission

BACKGROUND/OBJECTIVE

Cortisol is thought to be involved in the pathophysiology of affective disorders. Less attention has been given to other neuroendocrine factors. The aim of the present study was to test the hypothesis that adrenocortical steroids aldosterone and cortisol show different dynamic changes in the course of clinical depression with the assumption that aldosterone is a state marker of depression.

METHODS

A total of 78 adult subjects (39 patients with depressive disorder and 39 healthy controls) participated in a prospective non-interventional clinical study. Patients were investigated at the time of an acute episode and 6 months after reaching remission. The clinical and personal characteristics, and morning and evening salivary concentrations of aldosterone and cortisol were evaluated.

RESULTS

Patients with an acute depressive episode exhibited higher evening aldosterone and lower morning cortisol concentrations compared to healthy subjects. In these patients, both hormone concentrations showed flatter morning to evening slopes. Salivary aldosterone, but not cortisol concentrations, were lower in patients 6 months after reaching remission compared to those in the acute state. Similarly, 6 months of remission resulted in a steeper morning to evening slope of salivary aldosterone compared to the acute state. The cortisol rhythm remained dysregulated. A significant negative correlation between trait anxiety scores and morning cortisol concentrations in patients at 6 months of clinical remission was observed.

CONCLUSION

Diurnal changes in salivary aldosterone concentrations appear to be a state marker, whilst those of cortisol a trait marker of depression.

Post-weaning social isolation of rats induces reduction in the gene expression of vascular endothelial growth factor (VEGF) in the hippocampus

The role of vascular endothelial growth factor (VEGF) in chronic stress and neurodevelopmental disorders is of growing research interest. Here we show that post-weaning isolation rearing of rats decreased gene expression of VEGF in the hippocampus. Gene expression of VEGF upstream regulator fibroblast growth factor-2 (FGF-2) or its downstream mediator endothelial nitric oxide synthase (eNOS) was unchanged. Other signaling pathways appear to be involved in isolation-induced reduction in VEGF gene expression. Sex differences in VEGF and eNOS gene expression with significantly higher mRNA levels in females than males were revealed.

Brain derived neurotrophic factor expression and DNA methylation in response to subchronic valproic acid and/or aldosterone treatment

Aim

Methods

Results

Conclusion

Aldosterone and aldosterone/cortisol ratio is higher in serum of long-term compared to first episode schizophrenia patients: A pilot study

We have previously shown that patients with severe depressive episode exhibit higher aldosterone concentrations compared to those with moderate depressive episode. The present study was undertaken to test the hypothesis that circulating concentration of aldosterone reflect the clinical state in patients with schizophrenia. The sample consisted of 36 hospitalized patients (25 men, 11 women) with the first episode or long-term course of schizophrenia. The severity of psychopathology was evaluated using the Positive and Negative Syndrome Scale (PANSS). Samples for measurement of serum aldosterone were obtained immediately after awakening. The results showed that serum aldosterone concentrations were lower in patients with the first episode compared to those in patients with long-term course of schizophrenia. Importantly, lower aldosterone concentrations observed in patients with the first episode were associated with more severe clinical symptoms as indicated by all subscales of PANSS. Serum cortisol concentrations did not differ between the groups, while the aldosterone/cortisol ratio showed similar pattern as aldosterone concentrations. The present pilot study suggests that circulating aldosterone in patients with schizophrenia may reflect the severity of clinical symptoms but in an opposite direction than in patients with major depressive disorder.

Effect of Endocannabinoid Oleamide on Rat and Human Liver Cytochrome P450 Enzymes in In Vitro and In Vivo Models

The endocannabinoid system is important for many physiologic and pathologic processes, but its role in the regulation of liver cytochromes P450 (P450s) remains unknown. We studied the influence of the endocannabinoid oleamide on rat and human liver P450s. Oleamide was administered intraperitoneally to rats at doses of 0.1, 1, and 10 mg/kg per day for 7 days. The content and activity of key P450s were evaluated in rat liver microsomes. Moreover, interactions with nuclear receptors regulating P450 genes and serum levels of their ligands (prolactin, corticosterone, and free triiodothyronine) were tested in in vitro P450 inhibition assays. Decreased protein levels and metabolic activities of CYP1A2, CYP2B, and CYP2C11, along with a drop in metabolic activity of CYP2D2, were observed in animals treated with oleamide (10 mg/kg per day). The activities of CYP2C6, CYP2A, and CYP3A and the levels of hormones were not altered. In vitro, oleamide exhibited a weak inhibition of rat CYP1A2, CYP2D2, and CYP2C6. The activities of rat CYP2A, CYP2B, CYP2C11, and CYP3A and human CYP1A2, CYP2B6, CYP2C9, and CYP3A4 were not altered. Oleamide did not interact with human pregnane X, constitutive androstane, or aryl hydrocarbon receptors in reporter gene experiments and did not regulate their target P450 genes in primary human hepatocytes. Our results indicate that oleamide caused the downregulation of some rat liver P450s, and hormones are not mediators of this effect. In vitro oleamide inhibits mainly rat CYP2C6 and is neither an agonist nor antagonist of major human nuclear receptors involved in the regulation of xenobiotic metabolism.

Effects of vortioxetine on biomarkers associated with glutamatergic activity in an SSRI insensitive model of depression in female rats

The aim of this study was to investigate the antidepressant activity of vortioxetine in a tryptophan (TRP) depletion female rat model of depression and compare it to that of paroxetine using doses that fully occupy the serotonin transporter (SERT). We evaluated the effects of vortioxetine on potential biomarkers associated with TRP depletion including serum aldosterone, corticosterone and IL-6 levels together with indirect indicators of glutamate neurotransmission. Female Sprague-Dawley rats were randomized to control, low TRP, low TRP/paroxetine or low TRP/vortioxetine groups. Vortioxetine and paroxetine were administered via diet (10mg/kg/day) and drinking water (10mg/kg/day) respectively for 14days. Vortioxetine but not paroxetine reversed TRP depletion-induced depressive-like behavior. Vortioxetine reduced TRP depletion-induced increases of serum corticosterone, aldosterone, IL-6 and N-methyl-d-aspartate and α7-nicotinic acetylcholine receptor expression in the amygdala and hippocampus, respectively. Paroxetine demonstrated little effect except a reduction of aldosterone. Vortioxetine but not paroxetine reversed TRP depletion-induced reductions of serum and brain kynurenic acid. In conclusion, vortioxetine, but not paroxetine, enabled reversals of TRP depletion-induced changes of depression-like behavior and markers of glutamatergic activity. These observations support the hypothesis that vortioxetine's antidepressant activity may involve mechanisms beyond SERT inhibition.

Contrasting effects of vortioxetine and paroxetine on pineal gland biochemistry in a tryptophan-depletion model of depression in female rats

We studied the effects of the multi-modal antidepressant, vortioxetine and the SSRI, paroxetine on pineal melatonin and monoamine synthesis in a sub-chronic tryptophan (TRP) depletion model of depression based on a low TRP diet. Female Sprague-Dawley rats were randomised to groups a) control, b) low TRP diet, c) low TRP diet+paroxetine and d) low TRP diet+vortioxetine. Vortioxetine was administered via the diet (0.76mg/kg of food weight) and paroxetine via drinking water (10mg/kg/day) for 14days. Both drugs resulted in SERT occupancies >90%. Vortioxetine significantly reversed TRP depletion-induced reductions of pineal melatonin and serotonin (5-HT) and significantly increased pineal noradrenaline NA. Paroxetine did none of these things. Other studies suggest pineal melatonin synthesis may involve N-methyl-d-aspartate (NMDA) receptors and glutamatergic modulation. Here observed changes may be mediated via vortioxetine's strong 5-HT reuptake blocking action together with possible additional effects on glutamate neurotransmission in the pineal via NMDA receptor-modulation and possibly with added impetus from increased NA output.

Increased gene expression of selected vesicular and glial glutamate transporters in the frontal cortex in rats exposed to voluntary wheel running

Though positive effects of exercise on mood and well being are well recognised, the central regulatory mechanisms are still not fully understood. The present study was aimed to testing the hypothesis that voluntary wheel running activates the gene expression of glutamate transporters in the brain cortex of rats. The animals were assigned to the control and voluntary wheel running groups. Voluntary wheel running rats had free access to a stainless steel activity wheel for 3 weeks. The daily running distance gradually increased to 6.21 ± 1.05 km by day 21. Vesicular glutamate transporter 3 (VGLUT3) mRNA levels in the frontal cortex were significantly elevated in the group of running animals compared to the values in sedentary controls, while the expression of other vesicular transporters were unchanged. The concentrations of mRNA coding for glial glutamate transporter 1 (GLT-1), but not glutamate aspartate transporter (GLAST) were increased by running. Voluntary wheel running resulted in an elevation of plasma corticosterone and increased expression of brain derived neurotrophic factor (BDNF) in the frontal cortex. In conclusion, chronic voluntary wheel running results in increased gene expression of VGLUT3 and GLT-1 in the brain cortex without changes in other glutamate transporter subtypes.

Neuroendocrine Response to School Load in Prepubertal Children: Focus on Trait Anxiety

At the time of school-age, the most frequent stress stimuli are related to school environment and educational process. Anxiety may play a big role in coping with stressful situations associated with school load. To approach this issue, we performed a real-life study at school during the classwork. The sample consisted of 36 healthy children aged 10 years, which were divided to low and high trait anxiety group based on the median value of the anxiety score. The investigations were carried out in the classroom during a stress condition (final exams) and non-stress condition (without any exam). In the whole sample, the condition with exam was associated with higher cortisol and lower testosterone concentrations in saliva compared to the condition without exam. The activity of salivary alpha-amylase increased at the end of the exam. Anxious children showed higher concentrations of aldosterone and lower activity of alpha-amylase compared to children with low trait anxiety. Cortisol levels were higher in anxious children in the first morning samples before starting the lessons. Children with high and low trait anxiety did not differ in extraversion, neuroticism, as well as non-verbal intelligence and school success. Thus, the anxious children at school showed a more rapid decrease of anticipatory stress-induced cortisol concentrations, higher aldosterone levels, and lower alpha-amylase activities compared to non-anxious children. These changes, particularly high concentrations of aldosterone in children with high trait anxiety, may have an impact on their psychophysiological development.

Aldosterone concentrations in saliva reflect the duration and severity of depressive episode in a sex dependent manner

Evidence is accumulating that aldosterone may exert central actions and influence mental functions. The aim of the present study was to test the hypothesis that major depressive disorder affects the diurnal variation of salivary aldosterone and that aldosterone concentrations reflect the duration and severity of the depressive episode in a sex dependent manner. The sample consisted of 60 patients (37 postmenopausal women, 23 men) with major depressive disorder. Patients were examined two times, in acute depressive episode (admission to the hospital) and after reaching clinical remission (discharge). The samples of saliva were taken by the patients themselves twice a day (8.00-9.00 h in the morning and in the evening). Aldosterone concentrations were significantly higher in women compared to men and were significantly higher at the time of admission to the hospital compared to those at the discharge. Morning but not evening salivary aldosterone concentrations reflected the length of the depressive episode in women as well as the severity of the disorder in both sexes. Moreover, the patients with depression failed to exert known daily rhythmicity of aldosterone release. The present study brings several pieces of evidence suggesting the association of aldosterone with the pathophysiology of depression. Salivary aldosterone concentrations appear to reflect the outcome, the duration and the severity of the depressive episode in a sex dependent manner.

β3-Adrenergic receptors, adipokines and neuroendocrine activation during stress induced by repeated immune challenge in male and female rats

The main hypothesis of the study is that stress associated with repeated immune challenge has an impact on β₃-adrenergic receptor gene expression in the brain. Sprague-Dawley rats were intraperitoneally injected with increasing doses of lipopolysaccharide (LPS) for five consecutive days. LPS treatment was associated with body weight loss and increased anxiety-like behavior. In LPS-treated animals of both sexes, β₃-receptor gene expression was increased in the prefrontal cortex but not the hippocampus. LPS treatment decreased β₃-receptor gene expression in white adipose tissue with higher values in males compared to females. In the adipose tissue, LPS reduced peroxisome proliferator-activated receptor-gamma, leptin and adiponectin gene expression, but increased interleukin-6 expression, irrespective of sex. Repeated immune challenge resulted in increased concentrations of plasma aldosterone and corticosterone with higher values of corticosterone in females compared to males. Concentrations of dehydroepiandrosterone (DHEA) in plasma were unaffected by LPS, while DHEA levels in the frontal cortex were lower in the LPS-treated animals compared to the controls. Thus, changes of DHEA levels in the brain take place irrespective of the changes of this neurosteroid in plasma. We have provided the first evidence on stress-induced increase in β₃-adrenergic receptor gene expression in the brain. Greater reduction of β₃-adrenergic receptor expression in the adipose tissue and of the body weight gain by repeated immune challenge in male than in female rats suggests sex differences in the role of β₃-adrenergic receptors in the metabolic functions. LPS-induced changes in adipose tissue regulatory factors and hormone concentrations might be important for coping with chronic infections.

Early cognitive impairment along with decreased stress-induced BDNF in male and female patients with newly diagnosed multiple sclerosis

The aim of this study was to evaluate neuroendocrine activation during stress in patients with recently diagnosed multiple sclerosis before starting the immunomodulatory therapy (EDSS score≤2.0). We verified the hypothesis that certain cognitive and affective dysfunction is present already at this early stage of the disease. The sample consisted of 38 subjects, which involved patients who were recently diagnosed multiple sclerosis and age- and sex-matched healthy volunteers. Stroop test served as mental stress model enabling measurement of cognitive performance. Present results showed increased state anxiety, depression scores and poorer performance in the Stroop test in the group of patients compared to healthy subjects. The cognitive dysfunction was particularly evident in male patients with simultaneously decreased concentrations of the brain-derived neurotrophic factor (BDNF) in plasma. The patients at this stage of the disease have not yet developed the hyperactivity of the hypothalamic-pituitary-adrenocortical axis. They showed normal levels of plasma copeptin and reduced aldosterone response to mental stress test in women only. Concentrations of plasma copeptin were higher in men compared to women. Very early stages of multiple sclerosis are accompanied by disturbances in psychological well-being, mild cognitive dysfunction and decreased plasma concentrations of BDNF, particularly in male patients.

Metabolic effects of subchronic peripheral oxytocin administration in lean and obese zucker rats

Increasing evidence indicates a role of oxytocin in controlling energy metabolism. The aim of his study was to investigate oxytocin effects on obese phenotype in leptin-resistant Zucker fatty rats, focusing on glucose and lipid metabolism. Zucker fatty rats and their lean controls were treated with oxytocin (3.6 μg/100g body weight/day) by osmotic minipumps implanted subcutaneously for 2 weeks. Two-hours intraperitoneal glucose tolerance test was performed in fasting rats. Oxytocin decreased food intake in both phenotypes while body weight gain reduced only in obese animals. In obese rats oxytocin impaired hepatic insulin extraction and enhanced liver triglyceride accumulation. Moreover, in the skeletal muscle of lean rats oxytocin treatment downregulated insulin signal transduction by decreasing of insulin receptor substrate 1 protein level and stimulating of its serine phosphorylation. Concurrently, the gene expression of insulin receptor substrate 1 in the skeletal muscle and adipose tissue was downregulated by oxytocin. In obese rats, oxytocin reduced adipocyte size and normalised mRNA levels of both fatty acid binding protein 4 and fatty acid synthase but attenuated gene expression of glucose transporter 4. The present study in Zucker fatty rats demonstrated ambivalent effects of oxytocin treatment with predominantly negative impact on skeletal muscle insulin pathway in lean animals.

Psychosocial stress based on public speech in humans: is there a real life/laboratory setting cross-adaptation?

Repeated or chronic exposure to stressors is associated with changes in neuroendocrine responses depending on the type, intensity, number and frequency of stress exposure as well as previous stress experience. The aim of the study was to test the hypothesis that salivary cortisol and cardiovascular responses to real-life psychosocial stressors related to public performance can cross-adapt with responses to psychosocial stress induced by public speech under laboratory setting. The sample consisted of 22 healthy male volunteers, which were either actors, more precisely students of dramatic arts or non-actors, students of other fields. The stress task consisted of 15 min anticipatory preparation phase and 15 min of public speech on an emotionally charged topic. The actors, who were accustomed to public speaking, responded with a rise in salivary cortisol as well as blood pressure to laboratory public speech. The values of salivary cortisol, systolic blood pressure and state anxiety were lower in actors compared to non-actors. Unlike non-actors, subjects with experience in public speaking did not show stress-induced rise in the heart rate. Evaluation of personality traits revealed that actors scored significantly higher in extraversion than the subjects in the non-actor group. In conclusion, neuroendocrine responses to real-life stressors in actors can partially cross-adapt with responses to psychosocial stress under laboratory setting. The most evident adaptation was at the level of heart rate responses. The public speech tasks may be of help in evaluation of the ability to cope with stress in real life in artists by simple laboratory testing.

Adipogenesis and aldosterone: a study in lean tryptophan-depleted rats

Next to epithelial tissues, mineralocorticoid receptors are also expressed in adipose tissue and are involved in the process of adipogenesis. Mineralocorticoid receptors in adipose tissue are likely to be activated mainly by glucocorticoids. The aim of the present study was to test the hypothesis that the processes related to adipogenesis are modified under the conditions associated with high circulating aldosterone. We have made advantage of a model of depression based on tryptophan depletion in which we have previously demonstrated that the elevation of serum aldosterone precedes that of corticosterone. Sixty adult female Sprague-Dawley rats were fed either a low tryptophan diet or control diet for 4 (elevation of aldosterone only), 7 and 14 days (broader neuroendocrine activation) respectively. Gene expression of several adipogenic factors, CD31, interleukin-6, adiponectin, resistin and leptin were evaluated. Levels of mRNAs coding for adipogenic, angiogenic and inflammatory factors in adipose tissue were elevated at 4 and 7 days of tryptophan depletion. Additionally, gene expression of aldosterone sensing 11-β-hydroxysteroid dehydrogenase 2 and mineralocorticoid receptors were elevated. All changes disappeared at 14 days of tryptophan depletion. Synchronously an increase of adipose tissue mass was observed. Although direct evidence is not provided, observed changes in gene expression may be related to the action of aldosterone on mineralocorticoid receptors. Our findings represent the first data on any changes in gene expression in adipose tissue in animal models of depression.

Inhibition of fatty-acid amide hydrolyse (FAAH) exerts cognitive improvements in male but not female rats

OBJECTIVES

The endocannabinoid system is implicated in the regulation of various brain functions including cognition, memory, and behavior. It has been shown that inhibition of the endocannabinoid-degrading enzyme fatty acid amid hydrolase (FAAH) enhances the memory and learning in males. Given the fact that sexual dimorphism exists in the different components of the endocannabinoid system, the aim of this study was to test the hypothesis that cognition enhancing effect of the acute inhibition of FAAH by URB597 is gender dependent.

METHODS

In the study, 32 adult male and female Sprague-Dawley rats were used. They were treated with a single intraperitoneal injection of FAAH inhibitor URB597 (0.3 mg/kg) or vehicle 40 min before behavioral testing. The novel object recognition test was used as a working memory task to assess cognitive performance.

RESULTS

Neither the treatment nor the gender significantly affected the velocity, the total distance travelled and the time spent exploring the familiar object. The recognition of the object was influenced by both URB597 and gender. Male rats treated with URB597 displayed significantly increased novel object exploration compared to males treated with vehicle as well as to female rats treated with URB597. Single administration of URB597 significantly enhanced the recognition index in male, but not female rats.

CONCLUSIONS

The results demonstrate that the positive effects of FAAH inhibition on the cognition are gender dependent. It is likely that male rats are more vulnerable to the modulation of the endocannabinoid system than female rats.

Aldosterone Signals the Onset of Depressive Behaviour in a Female Rat Model of Depression along with SSRI Treatment Resistance

Depression is a serious condition that occurs more frequently in women and is often associated with treatment resistance. The main hypotheses of this study are that (a) aldosterone is an early marker of depression onset and (b) a tryptophan (TRP) depletion model of depression previously validated in male rats is treatment resistant in females. To explore possible underlying mechanisms, we have focused on factors shown to be altered in patients with treatment-resistant depression. Female Sprague-Dawley rats were treated with a control or low-TRP-containing diet for various time periods up to 21 days. The results show that aldosterone secretion increased after 4 days of TRP depletion and prior to corticosterone. Optimal effects of TRP depletion occurred at 14 days. In addition to neurochemical and behavioural changes observed previously in males, TRP depletion in females was associated with a significant decline in serum magnesium concentrations, increased serum interleukin-6, enhanced gene expression of orexin A in the frontal cortex and induced a rise in N-methyl-D-aspartate (NMDA) receptor Bmax in the amygdala. Depression-like behaviour, NMDA receptor upregulation, enhancement of the kynurenine-to-kynurenic acid ratio and magnesium were resistant to paroxetine treatment (10 mg/kg/day in drinking water for 14 days). In conclusion, aldosterone may represent an important early marker for the onset of depression-like behaviour. With respect to treatment resistance, the underlying mechanisms may involve pro-inflammatory cytokines, the kynurenine pathway, magnesium, glutamate neurotransmission and the orexin pathway. This model of treatment-resistant depression may be useful for the future development of new compounds with novel antidepressant properties.

Effect of blockade of mGluR5 on stress hormone release and its gene expression in the adrenal gland

The aim of this study was to verify the presence of metabotropic glutamate receptor subtype 5 (mGluR5) in the adrenal gland of male rats of 2 different strains, and to test the hypothesis that treatment with mGluR5 antagonist 2-methyl-6-(phenylethynyl)-pyridine (MPEP) affects hormone release and adrenal gene expression of mGluR5 under conditions of stress. The results clearly show the gene expression of mGluR5 in the adrenal gland in both the adrenal cortex and medulla. Treatment with the glutamate release inhibitor riluzole (4 mg·(kg body mass)(-1)·day(-1) for 2 weeks) failed to modify mRNA levels of either the mGluR5 or NR1 subunit of the NMDA receptor in the adrenal glands, as measured by real-time PCR. Blockade of mGluR5 with MPEP (1 mg·kg(-1) for 4 days) increased corticosterone but not catecholamine release during restraint stress (20 min). Treatment with MPEP had no effect on mRNA levels coding for steroidogenic factors StAR and SF-1, and decreased mGluR5 gene expression in the adrenal gland. In conclusion, mGluR5 is not likely to play a significant role in stress-induced catecholamine release. Pharmacological blockade of mGluR5 has a modest influence on the hypothalamic-pituitary-adrenocortical axis, as reflected in adrenal hypertrophy and increased corticosterone concentrations.

Increased anxiety induced by listening to unpleasant music during stress exposure is associated with reduced blood pressure and ACTH responses in healthy men

The relationship between anxiety and the neuroendocrine response to stress stimuli is still not fully understood. The aim of this study was to evaluate the contribution of an acute increase in state anxiety to neuroendocrine activation under stress conditions. To do so, it was necessary to find a stress condition of the same character and intensity with and without a rise in state anxiety. We decided to examine the effects of listening to music on anxiety and to apply a new methodological approach. A group of 14 healthy volunteers participated in a counterbalanced crossover design study. The stress procedure consisted of mental (Stroop test, mental arithmetic) and physical (handgrip exercise) tasks combined with listening to music played forward (pleasant) or backwards (unpleasant). The results confirmed our hypothesis, namely the condition with listening to unpleasant music was anxiogenic, while the other was not. In case of increased state anxiety, the rise in ACTH concentrations in response to mental challenge and the increase in systolic blood pressure induced by handgrip exercise was reduced compared to the situation with unchanged anxiety. Concentrations of testosterone, oxytocin, vasopressin and aldosterone were slightly increased in response to the stress paradigm accompanied with increased anxiety. In conclusion, the present data demonstrate that an acute increase in state anxiety contributes to neuroendocrine activation under stress conditions. Moreover, the results show that listening to music may both positively and negatively influence the perception of stress and the level of anxiety, which might have functional consequences.

Eplerenone, a selective mineralocorticoid receptor blocker, exerts anxiolytic effects accompanied by changes in stress hormone release

The aim of this study was to investigate the impact of chronic treatment with eplerenone, a mineralocorticoid receptor antagonist and clinically used antihypertensive drug, on animal correlates of mood disorders, namely anxiety-like behaviour, stress hormones release and brain plasticity. Male rats (n = 40) were injected subcutaneously twice daily with eplerenone (50 mg/kg body weight) or vehicle for 11 days. Open-field and elevated plus-maze tests were used as both anxiety-related paradigms and stress stimuli to evaluate hormone responses. Eplerenone-treated rats showed reduced anxiety-like behaviour manifested by both conventional and ethological parameters related to exploration and risk assessment behaviour in the elevated plus-maze test and partially in the open-field test. Eplerenone treatment resulted in an elevation of plasma aldosterone and oxytocin levels. Chronic treatment with eplerenone prevented the stress-induced rise in plasma corticosterone levels and vasopressin concentrations in the posterior pituitary. Eplerenone treatment failed to induce substantial changes in hippocampal brain derived neurotrophic factor protein concentrations. In conclusions, chronic treatment with eplerenone (1) exerts anxiolytic effects and (2) influences corticosterone, oxytocin and vasopressin concentrations in a manner consistent with the anxiolytic outcome.

Attenuated neuroendocrine response to hypoglycemic stress in patients with panic disorder

BACKGROUND/AIMS

There is a lack of information on the effects of metabolic stress exposure on hormone release in patients with panic disorder. The aim of this study was to test the hypothesis that neuroendocrine activation during hypoglycemic stress is altered in panic disorder patients compared to healthy subjects.

METHODS

Hormone responses to an intravenous bolus of insulin (0.1 IU/kg) were evaluated in both fully remitted, medication-free panic disorder patients and healthy controls (n = 9/group). Blood samples for determination of cortisol, growth hormone, prolactin, adrenaline and noradrenaline concentrations were obtained at rest and over a 90-min period after insulin injection.

RESULTS

In patients with panic disorder, basal prestress hormone levels were comparable to those in healthy subjects with the exception of plasma adrenaline, which was higher in panic disorder patients compared to controls. The degree of hypoglycemia induced by insulin administration was similar in patients and healthy subjects. Hypoglycemia-induced increases in growth hormone, prolactin and cortisol concentrations were significantly attenuated in panic disorder patients compared to healthy individuals. No differences between patients and controls were observed in adrenalin release induced by hypoglycemia.

CONCLUSIONS

The present data demonstrate that somatotropic, lactotropic and corticotropic activation during hypoglycemic stress is blunted in patients with panic disorder. It is suggested that in contrast to the effects of relatively mild stress conditions used in other studies published in the literature, intensive stressors inducing a broad spectrum of hormonal changes fail to provoke an adequate neuroendocrine response in patients with panic disorder.

Effect of single treatment with the antihypertensive drug eplerenone on hormone levels and anxiety-like behaviour in rats

OBJECTIVE

The aim of the study was to investigate the effects of single peripheral administration of mineralocorticoid receptor (MR) antagonist eplerenone on: 1. the hypothalamic-pituitary-adrenocortical (HPA) axis; 2. the renin-angiotensin-aldosterone (RAA) system, 3. anxiety-like behaviour.

METHODS

Male Wistar rats were injected subcutaneously with eplerenone (100 mg/kg body weight) or vehicle. Two hours following the injections, a half of the animals from each treatment group were decapitated to obtain blood for measurement of hormone levels. The other half of the animals was subjected to behavioural testing in the elevated plus-maze test. To provide comprehensive behavioural profile of eplerenone, standard spatiotemporal and ethologically derived measures of anxiety were assessed.

RESULTS

Single treatment with eplerenone resulted in a significant increase in plasma aldosterone levels. Plasma concentrations of ACTH and corticosterone were not modified by eplerenone injection. Administration of eplerenone failed to alter classical spatiotemporal measures of anxiety (number of entries and time spent in the open arms). However, ethological parameters related to exploration (head dipping) and risk assessment behaviour (stretched attend postures) were significantly affected by eplerenone injection.

CONCLUSIONS

Single injection of eplerenone is followed by a reduction of ethological indices of anxiety-like behaviour and by an elevation of plasma aldosterone levels. Acute administration of eplerenone appears to affect the RAA system but not hormones of the HPA axis.

Chronic treatment with the mineralocorticoid hormone aldosterone results in increased anxiety-like behavior

Aldosterone is the last component of the renin-angiotensin-aldosterone system inducing its peripheral effects via mineralocorticoid receptors (MR). Brain MR bind preferentially glucocorticoids. So far, the role of MR in behavioral functions has been investigated almost exclusively in relation to glucocorticoids. Recently, aldosterone itself has been linked to affective disorders. The aim of this study was to test the hypothesis that chronic elevation of circulating levels of aldosterone leads to increased anxiety. We have investigated the effects of chronic aldosterone treatment on (1) anxiety-like behavior, and (2) basal and stress-induced levels of selected hormones. Forty male Wistar rats were subcutaneously implanted with osmotic minipumps and treated with aldosterone (2 microg/100 g/day) or vehicle for two weeks. Aldosterone concentrations in plasma showed a mild (approximately four-fold) increase at the end of two-week aldosterone treatment. This mild hyperaldosteronism resulted in a significant enhancement of anxiety as demonstrated by alterations in all indicators of anxiety-like behavior measured in the open field and elevated plus-maze tests, without significant changes in measures of general locomotor activity. Aldosterone treatment affected not only the spatiotemporal measures of anxiety, but also the ethological parameters related to exploration and risk assessment. Chronic treatment with aldosterone was associated with increased water intake and decreased plasma renin activity, but failed to modify basal or stress-induced activity of the hypothalamic-pituitary-adrenocortical axis. The results provide evidence on anxiogenic action of prolonged increase in circulating aldosterone concentrations. Thus, aldosterone may represent an important target for future antidepressant and anxiolytic drug development.

Differences in home cage behavior and endocrine parametres in rats of four strains

OBJECTIVE

The majority of studies that involve behavioral testing in different rat strains is based on measuring behavioral responses to stressful situations in a novel environment. Very little is known on the spontaneous behavior in rat strains. The aim of the present study was to compare home cage behavior and basal hormone levels in two outbred rat strains, Sprague-Dawley (SD) and Wistar as well as two inbred strains, Lewis and Spontaneously Hypertensive Rats (SHR).

METHODS

Twenty-eight male rats from four strains of rats (n=7/strain) were used in this study. Behavior of each rat in his home cage was recorded by a video camera for 45 minutes during the dark phase of the day. The parameters considered included rearing, jumps, ambulation, grooming, feeding/drinking and no movements. Blood plasma was analyzed for aldosterone, plasma renin activity (PRA), adrenocorticotropin hormone (ACTH) and corticosterone by specific radioimmunoassays.

RESULTS

One-way ANOVA revealed significant inter-strain differences in counts of jumps and rearing. In comparison with Sprague-Dawley and Wistar rats, Lewis rats displayed significantly more jumps and rearing. Statistical analysis showed significant inter-strain differences in the levels of aldosterone and of plasma renin activity. The highest levels of aldosterone were found in Lewis rats. Plasma renin activity was significantly lower in SHR than in Sprague-Dawley rats. Correlation analysis failed to reveal any relationships between behavioral and endocrine parameters. Significant strain differences were observed also in relative weights of the spleen, adrenals and thymus.

CONCLUSION

Plasma renin activity and basal mineralocorticoid secretion did not show parallel pattern if compared among different rat strains. Locomotor activity in the home cage, which could represent general activity to be considered in evaluating emotional responses, was highest in the Lewis rats.

Oxytocin levels in the posterior pituitary and in the heart are modified by voluntary wheel running

We hypothesized that voluntary wheel running results in increased secretion of oxytocin, a peptide involved in the stress response. An additional hypothesis was that prolonged exercise affects oxytocin levels in the heart, which is in line with the potential role of oxytocin in cardiovascular functions. Voluntary wheel running lasted 3 weeks and daily running distances increased progressively reaching maximum levels about 8 km (Sprague-Dawley rats) and 4 km (Lewis strain). The exercise resulted in significant reduction of epididymal fat, slight increase in glucose transporter GLUT4 mRNA levels and significant enhancement of plasma density. Voluntary exercise failed to influence plasma oxytocin levels either in Lewis or Sprague-Dawley rats, but it resulted in a significant decrease of oxytocin concentrations in the posterior pituitary. Plasma oxytocin concentrations were not modified even if the measurements were made in the dark phase of the day. In voluntary wheel running Sprague-Dawley rats, the content of oxytocin in the right heart atrium was lower than in controls. Thus, the present findings demonstrate that prolonged voluntary wheel running results in a decrease in pituitary oxytocin content without evident changes in hormone concentrations in peripheral blood. However, prolonged exercise used has a significant impact on oxytocin levels in the heart.