Noradrenaline, dopamine, serotonin: different effects of psychological stress on brain biogenic amines in mice and rats

Maternal care behavior and physiology moderate offspring outcomes following gestational exposure to opioids

The opioid epidemic has resulted in a drastic increase in gestational exposure to opioids. Opioid-dependent pregnant women are typically prescribed medications for opioid use disorders ("MOUD"; e.g., buprenorphine [BUP]) to mitigate the harmful effects of abused opioids. However, the consequences of exposure to synthetic opioids, particularly BUP, during gestation on fetal neurodevelopment and long-term outcomes are poorly understood. Further, despite the known adverse effects of opioids on maternal care, many preclinical and clinical studies investigating the effects of gestational opioid exposure on offspring outcomes fail to report on maternal care behaviors. Considering that offspring outcomes are heavily dependent upon the quality of maternal care, it is important to evaluate the effects of gestational opioid exposure in the context of the mother-infant dyad. This review compares offspring outcomes after prenatal opioid exposure and after reduced maternal care and integrates this information to potentially identify common underlying mechanisms. We explore whether adverse outcomes after gestational BUP exposure are due to direct effects of opioids in utero, deficits in maternal care, or a combination of both factors. Finally, suggestions for improving preclinical models of prenatal opioid exposure are provided to promote more translational studies that can help to improve clinical outcomes for opioid-dependent mothers.

Comparative evaluation of natural neuroprotectives and their combinations on chronic immobilization stress-induced depression in experimental mice

The present study evaluates the potential of neuroprotective phytochemicals-rutin (R), resveratrol (Res), 17β-estradiol (17β-E2), and their different combinations against chronic immobilization stress (CIS)-induced depression-like behaviour in male albino mice. Here, the mice were exposed to stress via immobilization of their four limbs under a restrainer for 6 h daily until 7 days of the induction after 30 min of respective drug treatment in different mice groups. The result found the protective effect of these phytoconstituents and their combinations against CIS-induced depression due to their ability to suppress oxidative stress, restore mitochondria, HPA-axis modulation, neurotransmitter level, stress hormones, and inflammatory markers. Also, the combination drug regimens of these phytoconstituents showed synergistic results in managing the physiological and biochemical features of depression. Thus, these neuroprotective could be utilized well in combination to manage depression-like symptoms during episodic stress. Furthermore, such results could be well justified when administered in polyherbal formulation with these neuroprotective as major components. In addition, an advanced study can be designed at the molecular and epigenetics level using a formulation based on these neuroprotective.

Translation of Preclinical PET Imaging Findings: Challenges and Motion Correction to Overcome the Confounding Effect of Anesthetics

Preclinical brain positron emission tomography (PET) in animals is performed using anesthesia to avoid movement during the PET scan. In contrast, brain PET scans in humans are typically performed in the awake subject. Anesthesia is therefore one of the principal limitations in the translation of preclinical brain PET to the clinic. This review summarizes the available literature supporting the confounding effect of anesthesia on several PET tracers for neuroscience in preclinical small animal scans. In a second part, we present the state-of-the-art methodologies to circumvent this limitation to increase the translational significance of preclinical research, with an emphasis on motion correction methods. Several motion tracking systems compatible with preclinical scanners have been developed, each one with its advantages and limitations. These systems and the novel experimental setups they can bring to preclinical brain PET research are reviewed here. While technical advances have been made in this field, and practical implementations have been demonstrated, the technique should become more readily available to research centers to allow for a wider adoption of the motion correction technique for brain research.

Neurokinin-1 receptor antagonist reverses functional CNS alteration caused by combined γ-rays and carbon nuclei irradiation

BACKGROUND

Ionizing radiation (IR) is one of the major limiting factors for human deep-space missions. Preventing IR-induced cognitive alterations in astronauts is a critical success factor. It has been shown that cognitive alterations in rodents can be inferred by alterations of a psycho-emotional balance, primarily an anxiogenic effect of IR. In our recent work we hypothesized that the neurokinin-1 (NK1) receptor may be instrumental for such alterations.

OBJECTIVE

The NK1 receptor antagonist rolapitant and the classic anxiolytic diazepam (as a comparison drug) were selected to test this hypothesis on Wistar rats.

METHOD

Pharmacological substances were administered through intragastric probes. We used a battery of tests for a comprehensive ethological analysis. A high-performance liquid chromatography was applied to quantify monoamines content. An analysis of mRNA expression was performed by real-time PCR. Protein content was studied by Western blotting technique.

RESULTS

Our salient finding includes no substantial changes in anxiety, locomotor activity and cognitive abilities of treated rats under irradiation. No differences were found in the content of monoamines. We discovered a synchronous effect on mRNA expression and protein content of 5-HT2a and 5-HT4 receptors in the prefrontal cortex, as well as decreased content of serotonin transporter and increased content of tryptophan hydroxylase in the hypothalamus of irradiated rats. Rolapitant affected the protein amount of a number of serotonin receptors in the amygdala of irradiated rats.

CONCLUSION

Rolapitant may be the first atypical radioprotector, providing symptomatic treatment of CNS functional disorders in astronauts caused by IR.

Poria cocos water extract ameliorates the behavioral deficits induced by unpredictable chronic mild stress in rats by down-regulating inflammation

ETHNOPHARMACOLOGICAL RELEVANCE

Poria cocos is a medicinal mushroom of the Polyporaceae family with antioxidant and anti-inflammatory activities, which has been used for its sedative, diuretic and tonic effects in traditional medicine for several hundred years.

AIM OF STUDY

Considering that depression is an inflammatory related mental disease, this study investigated the antidepressant-like effects of water extract of P. cocos in a rodent animal model.

MATERIALS AND METHODS

Rats that were exposed to a forced swimming test (FST) for 28 consecutive days, and unpredictable chronic mild stress (UCMS) for five weeks underwent treatment with P. cocos water extract (PCW) (doses: 100, 300 and 900 mg/kg body weight [bw]; administered by gavage). Dopamine (DA), serotonin (5-HT) and their metabolites in the frontal cortex of rats were measured.

RESULTS

Our results firstly showed that sucrose preference during the UCMS paradigm was increased and immobility time in the FST was reduced with administration of PCW. In addition, PCW significantly attenuated UCMS-induced turnover rate of DA and 5-HT in the frontal cortex. Moreover, PCW inhibited UCMS-induced activated inflammatory response, reflected by reduced expression in the frontal cortex of p38, NF-κB and TNF-α.

CONCLUSIONS

Our results strongly suggest that PCW exhibits a potent antidepressant-like effect via regulation of monoaminergic neurotransmission and inactivation of inflammation, and that P. cocos may be considered as a traditional herbal potential medicine for the treatment of depression.

The effects of agomelatine and imipramine on liver cytochrome P450 during chronic mild stress (CMS) in the rat

BACKGROUND

The aim of our research was to determine the effects of chronic treatment with the atypical antidepressant agomelatine on the expression and activity of liver cytochrome P450 (CYP) in the chronic mild stress (CMS) model of depression, and to compare the results with those obtained for the first-generation antidepressant imipramine.

METHODS

Male Wistar rats were subjected to CMS for 7 weeks. Imipramine (10 mg/kg ip/day) or agomelatine (40 mg/kg ip/day) was administered to nonstressed or stressed animals for 5 weeks (weeks 3-7 of CMS). The levels of cytochrome P450 mRNA, protein and activity were measured in the liver.

RESULTS

Agomelatine and imipramine produced different broad-spectrum effects on cytochrome P450. Like imipramine, agomelatine increased the expression/activity of CYP2B and CYP2C6, and decreased the CYP2D activity. Unlike imipramine, agomelatine raised the expression/activity of CYP1A, CYP2A and reduced that of CYP2C11 and CYP3A. CMS modified the effects of antidepressants at transcriptional/posttranscriptional level; however, the enzyme activity in stressed rats remained similar to that in nonstressed animals. CMS alone decreased the CYP2B1 mRNA level and increased that of CYP2C11.

CONCLUSION

We conclude the following: (1) the effects of agomelatine and imipramine on cytochrome P450 are different and involve both central and peripheral regulatory mechanisms, which implicates the possibility of drug-drug interactions; (2) CMS influences the effects of antidepressants on cytochrome P450 expression, but does not change appreciably their effects on the enzyme activity. This suggests that the rate of antidepressant drug metabolism under CMS is similar to that under normal conditions.

Effect of Forced Physical Activity on the Severity of Experimental Colitis in Normal Weight and Obese Mice. Involvement of Oxidative Stress and Proinflammatory Biomarkers

Inflammatory bowel diseases are a heterogeneous group of disorders represented by two major phenotypic forms, Crohn’s disease and ulcerative colitis. Cross talk between adipokines and myokines, as well as changes in intestinal microcirculation, was proposed in pathogenesis of these disorders. C57BL/6 male mice were fed ad libitum for 12 weeks a standard (SD) or high-fat diet (HFD). After the adaptation period, two groups of animals fed SD or HFD were subjected to 6 weeks of the forced treadmill exercise and the experimental colitis was induced in both groups of sedentary and exercising mice fed SD and HFD by intra-colonic administration of 2,4,6-trinitrobenzenesulfonic acid. The disease activity index (DAI), colonic blood flow (CBF), the weight of animals, caloric intake, the mesenteric fad pad, the colonic oxidative stress markers malondialdehyde (MDA), reduced glutathione (GSH), and superoxide dismutase (SOD) activity and intestinal expression and protein content of proinflammatory markers were evaluated. Macroscopic and microscopic colitis in sedentary SD mice was accompanied by a significant fall in CBF and exacerbated in those fed a HFD. The contents of MDA, GSH, and SOD activity were significantly increased in both SD and HFD fed mice with treadmill exercise as compared with sedentary mice. In sedentary HFD mice a significant increase in the intestinal oxidative stress parameters and mucosal expression of IL-1β, TNF-α, IL-17, IFNγ, IL-6, and IL-10 protein were observed and these effects were aggravated in mice subjected to forced treadmill exercise. The mucosal expression of mRNA for TNF-α, IL-1β, iNOS, COX-2, SOD-1, SOD-2, GPx mRNAs, and the hypoxia inducible factor (HIF)-1α protein expression were upregulated in colonic mucosa of treadmill exercising HFD mice with colitis compared with those without exercise. We conclude that forced treadmill running exacerbates the severity of colonic damage in obese mice due to a fall in colonic microcirculation, an increase in oxidative stress, and the rise in expression and activity of proinflammatory biomarkers.

Role of Serotonin and Dopamine in Psoriasis: A Case-Control Study

BACKGROUND:

Psoriasis is a chronic inflammatory disease mediated by the immune system with increased proliferation of keratinocytes. The exact cause is unknown but as a multifactor, such as infection, trauma and psychological stress have been thought to play a role in its pathophysiology. Dopamine and serotonin are believed to have a strong role in stress conditions and also directly play a role in psoriasis.

AIM:

This study aimed to evaluate the role of dopamine, serotonin, and psychological stress in psoriasis.

METHODS:

This study used a case-control design involving 30 patients with psoriasis (as a case group) and 30 healthy controls in the Dermatology and Venereology Polyclinic of Sanglah General Hospital Denpasar during the period December 2016 to February 2017. All samples were taken for venous blood examination serum dopamine and serotonin and analysed using the ELISA method. Statistical analysis using an independent t-test, partial correlation, receiver operator characteristic (ROC) curve, and logistic regression model.

RESULT:

There were significant differences in serotonin, dopamine, and stress index levels between groups with psoriasis and non-psoriasis (102.68 ± 25.44 Vs. 154.17 ± 20.90; p < 0.001), (437.13 ± 164.83 Vs. 138.11 ± 89.51; p < 0.001), and (138.5 ± 27.80 Vs. 92.55 ± 42.97; p < 0.001). Significant negative correlation was found between serotonin level and stress index (r = -0.366; p = 0.016) and between serotonin and dopamine (r = -0.634; p < 0.001) but a positive correlation was found between dopamine and stress index (r = 0.459; p = 0.042). Serotonin and dopamine showed that it could be used as a biochemical predictive model for psoriasis (AUC > 0.7). Multivariable risk analysis model high serum dopamine was the most important risk factor for the occurrence of psoriasis (adjusted OR: 7.8; 95% CI: 3.45-15.57; p = 0.024)

CONCLUSION:

Serotonin and dopamine have a significant role in the pathophysiology of the occurrence of psoriasis, and psychological stress can affect psoriasis through its influence on serotonin and dopamine.

Establishment and evaluation of a novel mouse model of peri/postmenopausal depression

Women are believed to be more vulnerable to develop depressive symptoms during the perimenopause compared to postmenopause. The traditional bilateral ovariectomy and chronic mild stress (CMS) stimulation animal model produces a postmenopausal depressive-like state but the transition from perimenopausal period to postmenopausal period was ignored. Thus we establish a novel animal model in which the mice were stimulated by CMS for three months and removed the ovaries by two-step operation, and then evaluate whether this novel model could be much better for preclinical study used as a peri/postmenopause depressive model. The present study systemically evaluated the changes induced by two-step ovariectomy plus CMS in the mice. The depression-like behaviors, the levels of corticosterone, estrogen, pro-inflammatory factors, neurotransmitters, as well as brain-derived neurotrophic factor were determined; the changes of estrogen receptors, serotonin receptors, uterine weight and bone microarchitecture were also observed. The results show that the behaviors and biochemical indexes of mice changed gradually over time. Our study suggests that this two-step ovariectomy operation plus CMS successfully establishes a more reasonable peri/postmenopausal depression animal model which effectively simulates the clinical symptoms of peri/postmenopausal depressive women.

Akebia quinata Decaisne aqueous extract acts as a novel anti-fatigue agent in mice exposed to chronic restraint stress

ETHNOPHARMACOLOGICAL RELEVANCE

Akebia quinata Decaisne extract (AQE; Lardizabalaceae) is used in traditional herbal medicine for stress- and fatigue-related depression, improvement of fatigue, and mental relaxation.

AIM OF THE STUDY

To clarify the effects of AQE on stress-induced fatigue, we investigated the neuroprotective pharmacological effects of A. quinata Decaisne in mice exposed to chronic restraint stress.

MATERIALS AND METHODS

Seven-week old C57BL/6 mice chronically stressed by immobilization for 3 h daily for 15 d and non-stressed control mice underwent daily oral administration of AQE or distilled water. The open field, sucrose preference, and forced swimming behavioral tests were carried out once weekly, and immunohistochemical analyses of NeuN, brain-derived neurotrophic factor (BDNF), phosphorylated cAMP response element-binding (CREB) protein, and BDNF receptor tropomyosin receptor kinase B (TrkB) in striatum and hippocampus were performed at the end of the experimental period. Brain levels of serotonin, adrenaline, and noradrenaline as well as serum levels of corticosterone were measured.

RESULTS

Behavioral tests showed that treatment with AQE improved all lethargic behaviors examined. AQE significantly attenuated the elevated levels of adrenaline, noradrenaline, and serotonin in the brain and corticosterone, alanine transaminase, and aspartate transaminase levels in the serum. Histopathological analysis showed that AQE reduced liver injury and lateral ventricle size in restraint-stress mice via inhibition of neuronal cell death. Immunohistochemical analysis showed increased phosphorylation of CREB and expression of BDNF and its receptor TrkB in striatum and hippocampus. Chlorogenic acid, isochlorogenic acid A, and isochlorogenic acid C were identified as the primary components of AQE. All three agents increased expression of BDNF in SH-SY5Y cells and PC12 cells with H₂O₂-induced neuronal cell damage.

CONCLUSIONS

AQE may have a neuroprotective effect and ameliorate the effects of stress and fatigue-associated brain damage through mechanisms involving regulation of BDNF-TrkB signaling.

Erinacine A-Enriched Hericium erinaceus Mycelium Produces Antidepressant-Like Effects through Modulating BDNF/PI3K/Akt/GSK-3β Signaling in Mice

Antidepressant-like effects of ethanolic extract of Hericium erinaceus (HE) mycelium enriched in erinacine A on depressive mice challenged by repeated restraint stress (RS) were examined. HE at 100, 200 or 400 mg/kg body weight/day was orally given to mice for four weeks. After two weeks of HE administration, all mice except the control group went through with 14 days of RS protocol. Stressed mice exhibited various behavioral alterations, such as extending immobility time in the tail suspension test (TST) and forced swimming test (FST), and increasing the number of entries in open arm (POAE) and the time spent in the open arm (PTOA). Moreover, the levels of norepinephrine (NE), dopamine (DA) and serotonin (5-HT) were decreased in the stressed mice, while the levels of interleukin (IL)-6 and tumor necrosis factor (TNF)-α were increased. These changes were significantly inverted by the administration of HE, especially at the dose of 200 or 400 mg/kg body weight/day. Additionally, HE was shown to activate the BDNF/TrkB/PI3K/Akt/GSK-3β pathways and block the NF-κB signals in mice. Taken together, erinacine A-enriched HE mycelium could reverse the depressive-like behavior caused by RS and was accompanied by the modulation of monoamine neurotransmitters as well as pro-inflammatory cytokines, and regulation of BDNF pathways. Therefore, erinacine A-enriched HE mycelium could be an attractive agent for the treatment of depressive disorders.

Validation and optimisation of a touchscreen progressive ratio test of motivation in male rats

RATIONALE

Across species, effort-related motivation can be assessed by testing behaviour under a progressive ratio (PR) schedule of reinforcement. However, to date, PR tasks for rodents have been available using traditional operant response systems only.

OBJECTIVES

Touchscreen operant response systems allow the assessment of behaviour in laboratory rodents, using tasks that share high face validity with the computerised assessments used in humans. Here, we sought to optimise a rat touchscreen variant of PR and validate it by assessing the effects of a number of manipulations known to affect PR performance in non-touchscreen paradigms.

METHODS

Separate groups of male Sprague-Dawley rats were trained on PR schedules with either linear (PR4) or exponential (PREXP) schedules of reinforcement. PR performance was assessed in response to manipulations in reward outcome. Animals were tested under conditions of increased reward magnitude and following reward devaluation through a prefeeding procedure. Subsequently, the effects of systemic administration of the dopamine D2/D3 receptor antagonist raclopride and the psychostimulant d-amphetamine were examined as traditional pharmacological methods for manipulating motivation.

RESULTS

Rats reinforced under PR4 and PREXP schedules consistently showed differential patterns of response rates within sessions. Furthermore, both PR4 and PREXP schedules were sensitive to suppression by prefeeding or raclopride administration. Performance under both schedules was facilitated by increasing reward magnitude or d-amphetamine administration.

CONCLUSIONS

Taken together, these findings mirror those observed in lever-based PR paradigms in rats. This study therefore demonstrates the successful validation of the rat touchscreen PR task. This will allow for the assessment of motivation in rats, within the same touchscreen apparatus used for the assessment of complex cognitive processes in this species.

Neuroprotective effect of Clerodendrum serratum Linn. leaves extract against acute restraint stress-induced depressive-like behavioral symptoms in adult mice

Objective:

The objective of this study was to study the effect of ethanol extract of Clerodendrum serratum (EECS) Linn. on acute restraint stress (ARS)-induced depressive-like behavior and biochemical alterations in mice.

Materials and Methods:

Ethyl acetate and n-butanol fractions of EECS were analytically characterized for the flavonoid components, apigenin (API) and luteolin (LUT) by reverse-phase high-performance liquid chromatography. Behavioral tests, namely, forced-swim test and tail-suspension test were performed for assessing antidepressant-like effect and anxiolytic activity in mice. Oxidative stress parameters and biochemical alterations in mice brain tissue were also performed.

Statistical Analysis:

Expression of data was done as mean ± standard error of mean. The normally distributed data were subjected to two-way ANOVA followed by Dunnett's test. P < 0.05 was considered statistically significant.

Results:

The study showed that flavonoids, API and LUT were present in ethyl acetate and n-butanol fractions of EECS, which significantly reversed ARS-induced depressive-like behavior without affecting locomotion. EECS also attenuated oxidative damage caused by ARS. The level of norepinephrine and 5-hydroxytryptamine was also significantly restored by pretreatment with EECS for 7 days.

Conclusion:

EECS significantly alleviated ARS-induced depressive-like behavior without affecting locomotion.

Examination of Concurrent Exposure to Repeated Stress and Chlorpyrifos on Cholinergic, Glutamatergic, and Monoamine Neurotransmitter Systems in Rat Forebrain Regions

Repeated stress has been reported to cause reversible impairment in the central nervous system (CNS). It was proposed that alterations in glutamatergic, cholinergic, and monoamine neurotransmitter systems after exposure to stress are initial CNS events contributing to this impairment and that exacerbation could occur with concurrent exposure to cholinesterase inhibitors. Effects of concurrent exposure to repeated stress and chlorpyrifos on activities of acetylcholinesterase (AChE), carboxylesterase, and choline acetyltransferase (ChAT); concentrations of excitatory amino acids, monoamines, and their metabolites; and maximum binding densities ( Bmax) and equilibrium dissociation rate constants ( Kd) of glutamatergic N-methyl-d-aspartate (NMDA) and total muscarinic cholinergic receptors were studied in the blood, hippocampus, cerebral cortex, or hypothalamus of adult Long-Evans rats. Stress treatments extended over 28 days included (1) control rats handled 5 days/week; (2) rats restrained 1 h/day for 5 days/week; (3) rats swum 30 min for 1 day/week; or (4) rats restrained 4 days/week and swum for 1 day/week. On day 24, each stress treatment group was randomly divided and injected either with corn oil or chlorpyrifos, 160 mg/kg subcutaneously (sc) (60% of the maximum tolerated dose), 4 h after restraint. Blood and brain tisssues were collected on day 28. Rats restrained and swum had a statistical trend toward increasing concentrations of glutamate in the hippocampus when compared to rats only swum ( p = .064). Chlorpyrifos administration decreased restraint-induced elevated aspartate in the hippocampus, and decreased Bmax of total muscarinic receptors in the cerebral cortex. In addition, chlorpyrifos decreased Bmax and Kd of total muscarinic receptors in the cerebral cortex of swum rats. Results demonstrated that chlorpyrifos inhibited AChE activity in blood, cerebral cortex, and hippocampus, but stress did not affect AChE activity. Carboxylesterase activity was inhibited by chlorpyrifos and by repeated restraint with swim. Swim stress decreased concentrations of norepinephrine in the hippocampus and hypothalamus, and increased concentrations of dopamine and its metabolite, DOPAC, in the hypothalamus. Both stress and chlorpyrifos altered serotonin concentrations, and the interactions of repeated stress and chlorpyrifos on serotonin approached significance in the hippocampus ( p = .06) and hypothalamus ( p = .08). Therefore, stress models were demonstrated to alter glutamatergic and monoamine responses, whereas chlorpyrifos alone had effects on cholinergic and monoamine systems in the rat CNS. However, the interactions between stress and chlorpyrifos significant at p < 0.05 were restricted to attenuation of elevated aspartate in the hippocampus of restrained with swim rats and decreased Kd of acetylcholine receptors in the cerebral cortex of swum rats and restrained rats.

Organic cation transporter 3 (OCT3) is localized to intracellular and surface membranes in select glial and neuronal cells within the basolateral amygdaloid complex of both rats and mice

Organic cation transporter 3 (OCT3) is a high-capacity, low-affinity transporter that mediates corticosterone-sensitive uptake of monoamines including norepinephrine, epinephrine, dopamine, histamine and serotonin. OCT3 is expressed widely throughout the amygdaloid complex and other brain regions where monoamines are key regulators of emotional behaviors affected by stress. However, assessing the contribution of OCT3 to the regulation of monoaminergic neurotransmission and monoamine-dependent regulation of behavior requires fundamental information about the subcellular distribution of OCT3 expression. We used immunofluorescence and immuno-electron microscopy to examine the cellular and subcellular distribution of the transporter in the basolateral amygdaloid complex of the rat and mouse brain. OCT3-immunoreactivity was observed in both glial and neuronal perikarya in both rat and mouse amygdala. Electron microscopic immunolabeling revealed plasma membrane-associated OCT3 immunoreactivity on axonal, dendritic, and astrocytic processes adjacent to a variety of synapses, as well as on neuronal somata. In addition to plasma membrane sites, OCT3 immunolabeling was also observed associated with neuronal and glial endomembranes, including Golgi, mitochondrial and nuclear membranes. Particularly prominent labeling of the outer nuclear membrane was observed in neuronal, astrocytic, microglial and endothelial perikarya. The localization of OCT3 to neuronal and glial plasma membranes adjacent to synaptic sites is consistent with an important role for this transporter in regulating the amplitude, duration, and physical spread of released monoamines, while its localization to mitochondrial and outer nuclear membranes suggests previously undescribed roles for the transporter in the intracellular disposition of monoamines.

Anti-stress Activity of Ocimum sanctum: Possible Effects on Hypothalamic-Pituitary-Adrenal Axis

The present study investigated anti-stress potential of Ocimum sanctum in chronic variable stress (CVS) paradigm. Further, the possible mechanism of anti-stress was explored in vitro using cell and cell-free assays. Rats were administered O. sanctum followed by CVS regimen for a period of 16 days. On days 4, 8, 12, and 16, body weight and immobility time in forced swim test were measured. In addition, the possible inhibitory effect of O. sanctum and ursolic acid on cortisol release and CRHR1 receptor activity were studied in cell-based assays, while inhibitory effects on 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) and catechol-O-methyltransferase (COMT) were studied in cell-free assays. CVS group demonstrated less body weight gain and higher immobility time than O. sanctum administered groups, while oral administration of O. sanctum significantly increased body weight gain and decreased the immobility time. Further, O. sanctum and its constituents inhibited cortisol release and exhibited a significant CRHR1 receptor antagonist activity. Also, they had specific inhibitory activity towards 11β-HSD1 and COMT activity. Thus, O. sanctum was found to be effective in the management of stress effects, and anti-stress activity could be due to inhibition of cortisol release, blocking CRHR1 receptor, and inhibiting 11β-HSD1 and COMT activities. Copyright © 2016 John Wiley & Sons, Ltd.

Dopamine D2-Receptor Antagonists Down-Regulate CYP1A1/2 and CYP1B1 in the Rat Liver

Dopaminergic systems regulate the release of several hormones including growth hormone (GH), thyroid hormones, insulin, glucocorticoids and prolactin (PRL) that play significant roles in the regulation of various Cytochrome P450 (CYP) enzymes. The present study investigated the role of dopamine D₂-receptor-linked pathways in the regulation of CYP1A1, CYP1A2 and CYP1B1 that belong to a battery of genes controlled by the Aryl Hydrocarbon Receptor (AhR) and play a crucial role in the metabolism and toxicity of numerous environmental toxicants. Inhibition of dopamine D₂-receptors with sulpiride (SULP) significantly repressed the constitutive and benzo[a]pyrene (B[a]P)-induced CYP1A1, CYP1A2 and CYP1B expression in the rat liver. The expression of AhR, heat shock protein 90 (HSP90) and AhR nuclear translocator (ARNT) was suppressed by SULP in B[a]P-treated livers, whereas the AhRR expression was increased by the drug suggesting that the SULP-mediated repression of the CYP1 inducibility is due to inactivation of the AhR regulatory system. At signal transduction level, the D₂-mediated down-regulation of constitutive CYP1A1/2 and CYP1B1 expression appears to be mediated by activation of the insulin/PI3K/AKT pathway. PRL-linked pathways exerting a negative control on various CYPs, and inactivation of the glucocorticoid-linked pathways that positively control the AhR-regulated CYP1 genes, may also participate in the SULP-mediated repression of both, the constitutive and induced CYP1 expression. The present findings indicate that drugs acting as D₂-dopamine receptor antagonists can modify several hormone systems that regulate the expression of CYP1A1, CYP1A2 and CYP1B1, and may affect the toxicity and carcinogenicity outcome of numerous toxicants and pre-carcinogenic substances. Therefore, these drugs could be considered as a part of the strategy to reduce the risk of exposure to environmental pollutants and pre-carcinogens.

Effects of Valerianae Radix et Rhizoma extract on psychological stress in mice

Background:

The aim of this study was to identify the effects of Valerianae Radix et Rhizoma water extract (VRe) originated from Valeriana fauriei Briquet on reducing psychological stress (PS) on mice.

Objective:

Mice were put under PS with communication box method: Restraining mice and forcing to see other mice underfoot shock stress.

Materials and Methods:

Measurements on plasma corticosterone, noradrenaline and lipid peroxidation, and elevated plus-maze (EPM) tests were carried out to determine the effect of VRe administration on physiological and behavioral responses of mice.

Results:

VRe showed anxiolytic effects in plasma corticosterone, noradrenaline, and EPM transfer latency levels, but it did not show any significant effects on the other indicators.

Conclusion:

V. fauriei, which has been used as a natural anxiolytic drug, exerts positive effects in the communication box induced PS in mice.

A new stress model, a scream sound, alters learning and monoamine levels in rat brain

Most existing animal models for stress involve the simultaneous application of physical and psychological stress factors. In the current study, we described and used a novel psychological stress model (scream sound stress). To study the validity of it, we carried out acute and chronic scream sound stress. First, adult Sprague-Dawley (SD) rats were randomly divided into white noise, stress and background groups. The white noise group and stress group were treated with white noise and scream sound for 4h in the morning respectively. Compared with white noise and background groups, exposure to acute scream sound increased corticosterone (CORT) level and decreased latency in Morris water maze (MWM) test. The levels of noradrenaline (NE), dopamine (DA), 5-hydroxytryptamine (5-HT), 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA) were altered in the striatum, hypothalamus and hippocampus of stress rats. Second, adult SD rats were randomly divided into background and stress groups, which were treated with scream sound for three weeks. Exposure to chronic scream sound suppressed body weight gain, increased corticosterone (CORT) level, influenced the morphology of adrenal gland, improved spleen and thymus indices, and decreased latency in MWM test. NE, DA, DOPAC, HVA and 5-HIAA levels were also altered in the brain of stress rats. Our results suggested that scream sound, as a novel stressor, facilitated learning ability, as well as altered monoamine levels in the rat brain. Moreover, scream sound is easy to apply and can be applied in more animals at the same time.

Mechanistic study on the antidepressant-like effect of danggui-shaoyao-san, a chinese herbal formula

Danggui-Shaoyao-San (DSS), a famous Chinese herbal formula, has been widely used in the treatment of various diseases. Previous studies have shown that DSS produces antidepressant-like effect in rodents. This study aims to investigate the mechanism(s) underlying the antidepressant-like action of DDS. The results showed that DSS treatment significantly antagonized reserpine-induced ptosis in mice. In addition, DSS treatment significantly increased sucrose consumption in chronic unpredictable stress- (CUS-) treated mice. DSS treatment also markedly attenuated CUS-induced decreases in noradrenaline and dopamine concentrations in mouse brain. Furthermore, DSS treatment significantly reversed CUS-induced increase in serum malondialdehyde (MDA) content and decrease in serum superoxide dismutase (SOD) activity in mice. The results suggest that the antidepressant-like activity of DSS is probably mediated by the modulation of central monoamine neurotransmitter systems and the reduction of oxidative stress.

Cadmium and exposure to stress increase aggressive behavior

Environmental toxicants and stress influence the health and behavior of people from different parts of the world. In the present study, aggressive behavior was evaluated in rats exposed to cadmium (Cd) for four weeks and subjected to immobilization stress (IS) based on the resident/intruder paradigm. Latency to the first bite (LB), total number of attacks (NA), total duration of attack manifestations (DAM), and a composite aggression score (CAS) were used to assess aggressiveness. Cadmium concentrations in the blood and the brain were determined. We observed that the parameters of aggressiveness were not altered by either Cd or IS when administered separately. However, animals exposed to Cd+IS had increased NA, DAM, and CAS. Cadmium was detected in the blood and the brain after treatment and Cd+IS exposure modified Cd distribution in these tissues. These results suggest that exposure to low levels of Cd associated with stress may lead to increased aggressiveness in rats.

Repeated restraint stress increases IgA concentration in rat small intestine

The most abundant intestinal immunoglobulin and first line of specific immunological defense against environmental antigens is secretory immunoglobulin A. To better understand the effect of repeated stress on the secretion of intestinal IgA, the effects of restraint stress on IgA concentration and mRNA expression of the gene for the alpha-chain of IgA was assessed in both the duodenum and ileum of the rats. Restraint stress induced an increase in intestinal IgA, which was blocked by an adrenalectomy, suggesting a role of catecholamines and glucocorticoids. Whereas the blocking of glucocorticoid receptors by RU-486 did not affect the increased IgA concentration, it did reduce IgA alpha-chain mRNA expression in both segments, indicating a possible mediation on the part of glucocorticoids in IgA secretion by individual cells. Treatment with corticosterone significantly increased both the IgA concentration and IgA alpha-chain mRNA expression in ileum but not in duodenum, suggesting that glucocorticoids may act directly on IgA-antibody forming cells to increase IgA secretion in the former segment. A probable role by catecholamines was evidenced by the reduction in IgA concentration and IgA alpha-chain mRNA expression in both segments after a chemical sympathectomy with 6-hydroxydopamine (6-OHDA). Additionally, norepinephrine significantly reduced IgA alpha-chain mRNA levels but increased pIgR mRNA expression and IgA concentration in both intestinal segments. We propose that the increased intestinal IgA levels caused by repeated restraint stress is likely due to the effects of catecholamines on the transport of plgA across the epithelium.

Antidepressant effects of ginseng total saponins in the forced swimming test and chronic mild stress models of depression

Ginseng total saponins (GTS) are the major active components of Panax ginseng C.A. Meyer, which has been used as a popular tonic herb for 2000 years in Far East countries. In the present study, two classic animal models: the forced swimming test (FST) and the chronic mild stress (CMS) model were used to evaluate the antidepressant-like activities of GTS. It was observed that GTS at doses of 50 and 100 mg/kg significantly reduced the immobility time in the FST in mice after 7-day treatment. GTS also reversed the reduction in the sucrose preference index, decrease in locomotor activity as well as prolongation of latency of feeding in the novelty environment displayed by CMS rats. In addition, HPLC-ECD and immunohistochemical staining analysis indicated that the CMS-induced decrease in monoamine neurotransmitter concentration and brain-derived neurotrophic factor (BDNF) expression in the hippocampus were almost completely reversed by GTS. In conclusion, GTS exerts antidepressant-like effects in two highly specific and predictive animal models of depression. The activity of GTS in antidepression may be mediated partly through enhancing the monoamine neurotransmitter concentration and BDNF expression in the hippocampus.

Preventive action of Kai Xin San aqueous extract on depressive-like symptoms and cognition deficit induced by chronic mild stress

Kai Xin San (KXS), a traditional Chinese herbal medicine, has been used clinically for the treatment of depressive disorders and cognitive impairment for centuries. However, the effects of KXS on cognitive dysfunction induced by depression have not been evaluated scientifically. The present study aimed to explore the antidepressant-like and nootropic effects of an aqueous extract of KXS (at doses of 0.3, 0.9, and 2.7 g/kg/day) using chronic mild stress (CMS) as a model of depression. Depressive symptoms were analyzed using the sucrose-preference and novelty-induced inhibition of feeding tests. Cognitive function was evaluated using a two-way active avoidance task. Serum corticosterone and adrenocorticotropic hormone (ACTH) levels, acetylcholinesterase (AChE) protein expression in the hippocampus, and monoamine neurotransmitter concentrations in the prefrontal cortex and hippocampus were also determined to elucidate the neurochemical mechanisms. Experimental results showed that KXS aqueous extract significantly ameliorated the CMS-induced depressive symptoms, including the reduced preference index and prolonged latency to novelty-suppressed feeding. Simultaneously, KXS significantly reversed the CMS-induced decrease in the numbers of active avoidance and active movement distances and increase in the numbers of the passive avoidance and passive movement distances, thereby producing nootropic effects in the two-way active avoidance test. KXS also inhibited the increased AChE expression in the hippocampus, up-regulated the decreased monoamine neurotransmitter concentrations of both brain areas and reduced the elevated ACTH concentrations in the serum induced by CMS. Taken together, these results indicate that KXS exerts its antidepressant-like and nootropic effects in the CMS model by modulating the HPA axis, monoamine neurotransmitter and cholinergic systems.

Effects of chronic citalopram treatment on 5-HT1A and 5-HT2A receptors in group- and isolation-housed mice

Selective serotonin reuptake inhibitors (SSRI) are characterized by high clinical effectiveness and good tolerability. A 2-3 week delay in the onset of effects is caused by adaptive mechanisms, probably at the serotonergic (5-HT) receptor level. To analyze this in detail, we measured 5-HT(1A) and 5-HT(2A) receptor bindings in vitro after 3 weeks of citalopram treatment (20 mg/kg i.p. daily) in group-housed as well as isolation-housed mice, reflecting neurobiological aspects seen in psychiatric patients. Isolation housing increased somatodendritic (+52%) and postsynaptic (+30-95%) 5-HT(1A) as well as postsynaptic 5-HT(2A) receptor binding (+25-34%), which confirms previous findings. Chronic citalopram treatment did not induce alterations in raphe 5-HT(1A) autoreceptor binding, independent of housing conditions. Housing-dependent citalopram effects on postsynaptic 5-HT(1A) receptor binding were found with increases in group- (+11-42%) but decreases in isolation-housed (-11 to 35%) mice. Forebrain 5-HT(2A) receptor binding decreased between 11 and 38% after chronic citalopram administration, independent of housing conditions. Citalopram's long-term action comprises alterations at the postsynaptic 5-HT(1A) and 5-HT(2A) receptor binding levels. Housing conditions interact with citalopram effects, especially on 5-HT(1A) receptor binding, and should be more strongly considered in pharmacological studies. In general, SSRI-induced alterations were more pronounced and affected more brain regions in isolates, supporting the concept of a higher responsiveness in "stressed" animals. Isolation-induced receptor binding changes were partly normalized by chronic citalopram treatment, suggesting the isolation housing model for further analyses of SSRI effects, especially at the behavioral level.

Anorexia induced by activation of serotonin 5-HT4 receptors is mediated by increases in CART in the nucleus accumbens

Anorexia nervosa is a growing concern in mental health, often inducing death. The potential neuronal deficits that may underlie abnormal inhibitions of food intake, however, remain largely unexplored. We hypothesized that anorexia may involve altered signaling events within the nucleus accumbens (NAc), a brain structure involved in reward. We show here that direct stimulation of serotonin (5-hydroxytryptamine, 5-HT) 4 receptors (5-HT(4)R) in the NAc reduces the physiological drive to eat and increases CART (cocaine- and amphetamine-regulated transcript) mRNA levels in fed and food-deprived mice. It further shows that injecting 5-HT(4)R antagonist or siRNA-mediated 5-HT(4)R knockdown into the NAc induced hyperphagia only in fed mice. This hyperphagia was not associated with changes in CART mRNA expression in the NAc in fed and food-deprived mice. Results include that 5-HT(4)R control CART mRNA expression into the NAc via a cAMP/PKA signaling pathway. Considering that CART may interfere with food- and drug-related rewards, we tested whether the appetite suppressant properties of 3,4-N-methylenedioxymethamphetamine (MDMA, ecstasy) involve the 5-HT(4)R. Using 5-HT(4)R knockout mice, we demonstrate that 5-HT(4)R are required for the anorectic effect of MDMA as well as for the MDMA-induced enhancement of CART mRNA expression in the NAc. Directly injecting CART peptide or CART siRNA into the NAc reduces or increases food consumption, respectively. Finally, stimulating 5-HT(4)R- and MDMA-induced anorexia were both reduced by injecting CART siRNA into the NAc. Collectively, these results demonstrate that 5-HT(4)R-mediated up-regulation of CART in the NAc triggers the appetite-suppressant effects of ecstasy.

Rapid neuroendocrine responses evoked at the onset of social challenge

At the onset of agonistic social challenge, individuals must assess the degree of threat the opponent represents in order to react appropriately. We aimed to characterize the neuroendocrine changes accompanying this period of initial social assessment using the lizard Anolis carolinensis. Conveyance of aggressive intent by male A. carolinensis is facilitated by rapid postorbital skin darkening (eyespot), whereas eyespot presence inhibits opponent aggression. By manipulating this visual signal, we also investigated whether differing neuroendocrine changes were evoked by initial presentation of varying levels of social threat. Subjects were painted postorbitally either with black paint (high threat level), green paint (low threat level) or water (controls). Painted animals were presented with a mirror and sampled immediately upon exhibiting aggressive intent towards the reflected simulated opponent, but before producing behaviors such as motor pattern-based displays. Control animals (blank surface presented) were sampled at times derived from averaging response times of painted subjects. Brains and plasma were analyzed for monoamine activity and catecholamine levels using electrochemical HPLC. Social threat evoked increases in plasma catecholamine levels indistinguishable from those caused by brief environmental disturbance. However, brief social challenge caused distinct rapid increases in amygdala and nucleus accumbens (NAc) dopamine and serotonin levels. Amygdalar changes were associated with general social threat presence, but NAc monoamines were affected by both threat level and subject motivation to engage in confrontation. This suggests that specific rapid activity changes in key forebrain limbic nuclei differ according to the degree of social threat perceived at the start of the interaction.

Effects of high dose of simvastatin on levels of dopamine and its reuptake in prefrontal cortex and striatum among SD rats

Statins are increasingly being used for the treatment of a variety of conditions beyond their original indication for cholesterol lowering. We previously reported that simvastatin increased dopamine receptors in the rat prefrontal cortex [Q. Wang, W.L. Ting, H. Yang, P.T. Wong, High doses of simvastatin upregulate dopamine D(1) and D(2) receptor expression in the rat prefrontal cortex: possible involvement of endothelial nitric oxide synthase, Br. J. Pharmacol. 144 (2005) 933-939] and restored its downregulation in a model of Parkinson's disease (PD) [Q. Wang, P.H. Wang, C. McLachlan, P.T. Wong, Simvastatin reverses the downregulation of dopamine D1 and D2 receptor expression in the prefrontal cortex of 6-hydroxydopamine-induced Parkinsonian rats, Brain Res. 1045 (2005) 229-233]. Here we explore the effects of simvastatin treatment on tissue dopamine content and reuptake. Sprague-Dawley rats were given simvastatin (1 and 10 mg kg(-1)day(-1), p.o.) for 4 weeks. Brain tissue from prefrontal cortex and striatum were taken out for dopamine content and its reuptake. Using high-performance liquid chromatographic-mass spectrometer (HPLC-MS), simvastatin (10 mg kg(-1)day(-1)) was found to increase dopamine content by 110% in the striatum but decreased by 76% in the prefrontal cortex compared with the saline treated group. Dopamine (DA) reuptake was unchanged in both brain regions. These results suggest that chronic treatment with high dose of simvastatin may affect DA tissue level in prefrontal cortex and striatum without changing on DA reuptake. This may have important clinical implications in psychiatric and striatal dopaminergic disorders.

CRF and stress in fish

The endocrine stress response is pivotal in vertebrate physiology. The stress hormone cortisol-the end product of the endocrine stress axis-(re-)directs energy flows for optimal performance under conditions where homeostasis may be or become at risk. Key players in the continuous adaptation process are corticotropin-releasing factor (CRF) from the hypothalamic nucleus preopticus (NPO), pituitary adrenocorticotropic hormone (ACTH) and cortisol produced by the interrenal cells in the headkidney (adrenal equivalent of fish). CRF is a member of a large family of related peptides that signals through CRF-receptor subtypes specific for central and peripheral actions of the peptide. CRF is "chaperoned" by a unique and phylogenetically very well-conserved binding protein (CRFBP); the functions of the CRFBP can only be speculated on so far, but its mRNA and protein abundance are important indicators of the central CRF-system activity, and indeed its mRNA levels are altered by restraint stress. Moreover, the unique structure and size of the CRFBP provide good tools in phylogenetic studies, that date the CRF-system to at least one billion years old. Pro-opiomelanocortin is produced and processed to ACTH and endorphin in the hypothalamic NPO and pituitary pars distalis ACTH-cells, to MSH and acetylated endorphins in the pituitary pars intermedia MSH-cells. ACTH is the prime corticotrope in acute stress conditions. In carp, MSH, considered a mild corticotrope in chronic stress responses in other fish, lacks corticotropic effects (in line with the absence of the melanocortin-5 receptor in headkidney); yet, an unknown corticotropic signal substance in the pars intermedia of carp awaits elucidation. Interesting observations were made on the CRF control of pituitary cells. CRF stimulates ACTH-cells, but only when these cells experience a mild dopaminergic block. Endorphin, produced in the NPO and transported via axons to the pituitary gland in vivo, reverses the stimulatory CRF action on MSH-cells to a differential inhibition of N-acetyl beta-endorphin release in vitro (MSH release is not affected). We speculate that the consistently observed elevation of plasma MSH during chronic stress may exert central actions related to feeding and leptin regulated processes. A BOLD-fMRI study revealed the functional anatomy of the stress response at work in a paradigm, where carp were exposed to a sudden water temperature drop. In carp (and other fish), the endocrine stress axis is already operational in very early life stages, viz., around hatching and comprises hypothalamic, pituitary, and interrenal signaling to adjust the physiology of the hatchling to its dynamically changing environment. Understanding of stress during early life stages is critical as the consequent rises in cortisol may have long lasting effects on survival and fish quality.

Cytokines, stressors, and clinical depression: augmented adaptation responses underlie depression pathogenesis

By influencing the central nervous system, cytokines, which regulate immune function innately and adaptively, may play a key role in mediating depression-like neuro-behavioral changes. However, the similarity between cytokine and stressor-effects in animal models raises a question about the degree to which behavioral and neurochemical outcomes of cytokine challenge represent depressive disorder per se. The present review attempts to illustrate the degree of overlap between cytokines and stressors with respect to their effects on neurochemistry and behavior in animal models. The review also shows how short-term effects of cytokine exposure in typical animals may be discerned from characteristics that might otherwise be described as depression-like. By comparing outcomes of immune challenge in typical rodent strains (e.g., Sprague-Dawley [SD], Wistar) and an accepted animal model of depression (e.g., Fawn Hooded [FH] rodent strain), differences between short-term effects of cytokines and depression-like characteristics in rodents are demonstrated. Additionally, because it is known that preexisting vulnerability to depression may affect outcomes of immune challenge, we further compare immunological, biochemical and behavioral effects of cytokines between SD and FH rodent strains. Interestingly, the acute neurochemical and behavioral effects of the cytokine interleukin 1alpha (IL-1alpha) reveal stressor-like responses during behavioral habituation in both strains, though this appears to a stronger degree in FH animals. Further, the subacute response to IL-1alpha vastly differed between strains, indicating differences in adaptive mechanisms. Thus, stressor-like effects of immune challenge, particularly in FH animals, provide validation for recent "cross-sensitization" models of depression pathogenesis that incorporate immune factors.

The corticotropin-releasing factor (CRF)-system and monoaminergic afferents in the central amygdala: investigations in different mouse strains and comparison with the rat

Corticotropin-releasing-factor (CRF) containing systems and monoaminergic afferents of the central amygdaloid nucleus (Ce) are crucial players in central nervous stress responses. For functional analyses of specific roles of these systems, numerous mouse models have been generated which lack or overexpress individual signal transduction components. Since data concerning system morphologies in murine brain are rarely available, mouse studies are usually designed and interpreted based on previous findings in rats, although interspecies differences are frequent. In the present study, in situ hybridization for CRF mRNA and correlative immunocytochemistry for CRF and monoaminergic afferents revealed numerous CRF mRNA-reactive neurons in the lateral Ce subnucleus (CeL) codistributed with dense dopaminergic fiber plexus in mice as has been demonstrated in rats. However, while in rats the lateral capsular Ce (CeLc) displays only scarce CRF immunoreactive (CRF-ir) innervation, particularly dense CRF-ir fiber plexus were observed in the CeLc in mice, with differences in labeling densities between different strains. CRF-ir terminal fibers overlap with the moderate serotonergic innervation of this subnucleus in mice. Additionally, CRF mRNA-reactive neurons were found immediately dorsal to the amygdala in the region of the interstitial nucleus of the posterior limb of the anterior commissure/amygdalostriatal transition area in both species. In mice, this region displayed dense CRF-ir fiber plexus, with variations between the strains. The results indicate that in mice and rats dopaminergic afferents represent the primary monoaminergic input to the CRF neurons in the CeL. In mice only, CRF-ir afferents provide dense innervation of CeLc neurons. Since the CeLc lacks dopaminergic input in both species but possesses moderate serotonergic afferents, CRF/serotonin interactions may occur selectively in mouse CeLc. The observed interspecies and interstrain differences in CRF input and CRF/monoaminergic interactions may influence the interpretation of findings concerning Ce functions in stress and fear in mouse models.

Effect of anaesthetics[sol ]terminal procedures on neurotransmitters from non-dosed and aroclor 1254-dosed rats

Subtle effects of low-dose exposure to environmental toxicants may be altered or masked by an inappropriate choice of anaesthesia prior to manipulation or termination of experimental animals. This study was designed to investigate effects of various anaesthetics and terminal procedures on neurotransmitters from male Sprague-Dawley rats. Significant changes in neurotransmitters were observed in the caudate nucleus, nucleus accumbens, hippocampus and substantia nigra but not the frontal cortex upon exposure to isoflurane, an Equithesin-like mixture or carbon dioxide relative to control animals that were decapitated without anaesthesia. Terminal use of any of these three anaesthetics also masked or altered some of the changes induced by exposure to Aroclor 1254. These results suggest that it is critical to avoid anaesthetizing experimental animals and that decapitation is the preferred method for euthanasia when conducting neurochemical studies.

Attenuated response to stress and novelty and hypersensitivity to seizures in 5-HT4 receptor knock-out mice

To study the functions of 5-HT4 receptors, a null mutation was engineered in the corresponding gene. 5-HT4 receptor knock-out mice displayed normal feeding and motor behaviors in baseline conditions but abnormal feeding and locomotor behavior in response to stress and novelty. Specifically, stress-induced hypophagia and novelty-induced exploratory activity were attenuated in the knock-out mice. In addition, pentylenetetrazol-induced convulsive responses were enhanced in the knock-out mice, suggesting an increase in neuronal network excitability. These results provide the first example of a genetic deficit that disrupts the ability of stress to reduce feeding and body weight and suggest that 5-HT4 receptors may be involved in stress-induced anorexia and seizure susceptibility.

Stress-mediated modulation of B(α)P-induced hepatic CYP1A1: role of catecholamines

The present study investigated the involvement of catecholamines in stress-mediated alterations in CYP1A1 induction by benzo(alpha)pyrene (B(alpha)P) in Wistar rats. This was achieved by measuring EROD activity and CYP1A1 mRNA levels in liver tissue from rats exposed to restraint stress and B(alpha)P coupled with pharmacological modulation of peripheral and central catecholamine levels and different adrenoceptors. In a state of reserpine-induced central and peripheral catecholamine depletion, stress strongly suppressed EROD induction. Peripheral catecholamines do not appear to play a critical role in the stress-mediated modulation of EROD inducibility by B(alpha)P. Stress did not alter EROD inducibility by B(alpha)P when peripheral catecholamines were either depleted by guanethidine or supplemented by peripheral adrenaline administration. On the other hand, central noradrenergic systems appear to have a role in the stress-mediated changes in B(alpha)P-induced EROD activity and Cyp1A1 gene expression. Stimulation or blockade of noradrenaline release with atipamezole and dexmedetomidine, respectively, significantly modified the up-regulating effect of stress. Alpha1 adrenoceptors also appear to participate in the effect of stress on EROD inducibility. Alpha1-blockade with prazosin potentiated the up-regulating effect of stress, possibly preventing the down-regulating effect of noradrenaline. Beta adrenoceptors also seem to be involved directly or indirectly in the stress-mediated modulation of Cyp1A1, as propranolol (beta-antagonist) blocked the down-regulating effect of stress on B(alpha)P-induced Cyp1A1 gene expression. Plasma corticosterone alterations after stress were not related to alterations in the B(alpha)P-induced EROD activity and Cyp1A1 gene expression. In conclusion, stress appears to interfere in the regulation of B(alpha)P-induced hepatic CYP1A1 in an unpredictable manner and via signalling pathways not always directly related to catecholamines. In particular, whenever drug treatment disrupts noradrenergic neurotransmission, other stress-stimulated factors appear to modify the induction of CYP1A1. In summary, regulation of induction of hepatic CYP1A1 during stress appears to involve various components of the stress system, including central and peripheral catecholamines, which interact in a complex manner, yet to be elucidated.

The efficacy of reboxetine in preventing and reverting a condition of escape deficit in rats

BACKGROUND

Different stress-induced experimental models of depression are currently used to study the efficacy and mechanism of action of classical or potential antidepressant compounds. We studied the effect of single and repeated administrations of reboxetine, an antidepressant that selectively inhibits noradrenaline reuptake, in the prevention and reversal of stress-induced escape deficit. Moreover, we examined the effect of chronic reboxetine on the stress-induced decrease of dopamine output in the nucleus accumbens shell (NAcS).

METHODS

Rats received a single or 21-day reboxetine administration before acute unavoidable stress exposure; 24 hours later their escape response was examined. Rats were exposed to repeated unavoidable stress for 21 days, with or without reboxetine treatment, and then were tested for escape; 2 days later they were implanted with microdialysis probes in the NAcS.

RESULTS

A single reboxetine administration showed a protective activity on stress-induced escape deficit development that significantly increased after 21 days of treatment. This effect was antagonized by propranolol, a selective beta-adrenergic antagonist. In rats exposed to chronic stress, a 21-day reboxetine treatment reinstated the avoidance response and NAcS dopamine output to control values.

CONCLUSIONS

In these stress-induced models, long-term reboxetine administration showed a protective activity similar to that of classical antidepressants.

Anxiolytic-like effects of 5-HT2 ligands on three mouse models of anxiety

The behavioural effects of 5-HT(2) receptor agonists, 5-HT(2A) and 5-HT(2C) receptor antagonists were investigated in the mouse four plates test (FPT), light/dark paradigm (L/D) and the elevated plus maze (EPM), in order to elucidate the role of the 5-HT(2) receptor subtypes in these models and to address the inconclusive results previously reported using rat psychopharmacological models. All compounds were administered intraperitoneally 30 min before each test. DOI, a preferential 5-HT(2A) agonist (0.5-8 mg/kg) and BW 723C86, a 5-HT(2B) agonist (8 and 16 mg/kg) provoked an anxiolytic-like response in the FPT. In the EPM, an anxiolytic-like effect was observed for DOI (0.5, 1 and 2 mg/kg), BW 723C86 (0.5, 4, 8 and 16 mg/kg), RO 60-0175 a 5-HT(2C) agonist (4 mg/kg) and the non-selective 5-HT(2) receptor agonist mCPP (0.25 mg/kg.). Ketanserin, a 5-HT(2A/2C) non-selective receptor antagonist (0.015 and 0.03 mg/kg), induced an anxiogenic-like effect in the L/D paradigm. The 5-HT(2C) antagonists (RS 10-2221, SDZ SER082 and SB 206553) were without effect in all three tests. These behavioural results are indicative of an anxiolytic-like action of 5-HT(2) receptor agonists, an anxiogenic-like effect of 5-HT(2A) receptor antagonism, whereas the blockade of 5-HT(2C) receptors are without effect in the mouse models studied.

Modulation of the stress response by coffee: an in vivo microdialysis study of hippocampal serotonin and dopamine levels in rat

We studied whether coffee and its components (caffeine and chlorogenic acid) have stress-relaxing effects. In vivo brain microdialysis was used to characterize the effects of coffee, stress, and their interaction on the serotonergic and dopaminergic systems in the rat hippocampus. Restraint stress for 100 min caused a marked increase in dopamine and serotonin (5-HT) levels in the hippocampus, and then, 100 min resting (freely-moving) time reduced them to basal levels. Pretreatment with 33 mg/kg coffee or 1.7 mg/kg caffeine reduced the second restraint-induced increase in the neurotransmitters, especially 5-HT, but neither saline nor 1.7 mg/kg chlorogenic acid did. These results suggest that coffee contributes to the reduction of restraint-induced stress and that these effects could be due to caffeine. Possible mechanisms of the effects are considered.