Efeitos agudos da restrição, choque e treinamento no labirinto elevado em T nos sistemas de noradrenalina e serotonina no córtex pré-frontal

The prefrontal cortex (PFC) participates in cognitive functions and stress regulation. Noradrenaline (NA) and serotonin (5-HT) levels in some regions of the central nervous system are modified by acute stress. The effects depend on the type of stressor and the time elapsed between the presence of the stressor and the assessment. The aims of the present study were to assess the acute effect of different stressors on NA and 5-HT activities in the PFC and its relation with corticosterone levels. Independent groups of male Wistar rats (250-280 g) were submitted to restraint, footshock or training in the elevated T-maze (ETMT). The animals were sacrificed immediately (T0) or one hour (T1) after stress exposure. An untreated group sacrificed concurrently with treated animals was included as control. Samples of the PFC were dissected and the concentration of NA, 5-HT and their metabolites were measured by HPLC. Corticosterone levels were measured in serum. None of the treatments modified NA levels in the PFC. Animals exposed to footshock or ETMT showed significantly higher concentrations of 5-HT at T0. Restraint and footshock treatments were associated with higher corticosterone levels at T0 and T1 after the respective treatment. Taken together the results show that in the PFC, the noradrenergic and serotonergic systems, and the corticosterone levels respond in different ways to different stressors.La corteza prefrontal (CPF) participa en las funciones cognitivas y la regulación del estrés. Las concentraciones de noradrenalina (NA) y serotonina (5-HT) en algunas regiones en el sistema nervioso central son modificadas por el estrés agudo. El efecto depende del estresor y del tiempo que transcurra entre el estresor y la evaluación. El objetivo del presente estudio fue evaluar el efecto agudo de diferentes estresores en la actividad de la NA y 5-HT en la CPF y su relación con los niveles de corticosterona. Grupos independientes de ratas (250-270 g) fueron sometidos a restricción, choque o entrenamiento en el laberinto elevado en T (ELET). Los animales fueron sacrificados inmediatamente (T0) o una hora (T1) después de la exposición al estrés. Un grupo no tratado, sacrificado al mismo tiempo que los animales tratados, se incluyó como control. Las muestras de la CPF fueron disecadas y la concentración de NA, 5-HT y sus metabolitos fue detectada por la técnica de HPLC. Las concentraciones de corticosterona fueron medidas en el suero. Ninguno de los tratamientos modificó las concentraciones de NA en la CPF. Al T0 los animales expuestos a choque o al ELET mostraron concentraciones de 5-HT significativamente mayores que el control. Los tratamientos de restricción y choque estuvieron asociados con altas concentraciones de corticosterona al T0 y a T1 después del tratamiento respectivo. En conjunto, los resultados mostraron que en la CPF los sistemas noradrenérgico y serotonérgico y la concentración de corticosterona responden en forma diferente a los distintos estresores.O córtex pré-frontal (CPF) participa nas funções cognitivas e na regulação do estresse. As concentrações de noradrenalina (NA) e serotonina (5-HT) em algumas regiões do sistema nervoso central são modificadas pelo estresse agudo. O efeito depende do estressor e do tempo que transcorra entre o estressor e a avaliação. O objetivo do presente estudo foi avaliar o efeito agudo de diferentes estressores na atividade da NA e 5-HT no PFC e sua relação com os níveis de corticosterona. Grupos independentes de ratos (250-270 g) foram submetidos a restrição, choque ou treinamento no labirinto elevado em T (ELET). Os animais foram sacrificados imediatamente (T0) ou uma hora (T1) depois da exposição ao estresse. Um grupo não tratado, sacrificado ao mesmo tempo que os animais tratados, incluiu-se como controle. As mostras do PFC foram dissecadas e a concentração de NA, 5-HT e seus metabolitos foi detectada pela técnica de HPLC. As concentrações de corticosterona foram medidas no soro. Nenhum dos tratamentos modificou as concentrações de NA no PFC. Em T0 os animais expostos a choque o ao ELET mostraram concentrações de 5-HT significativamente maiores que o controle. Os tratamentos de restrição e choque estiveram associados com altas concentrações de corticosterona em T0 e em T1 depois do tratamento respectivo. Em conjunto, os resultados mostraram que no PFC os sistemas noradrenérgico e serotonérgico e a concentração de corticosterona respondem de maneira diferente aos diferentes estressores

Behavioral and Autonomic Responses to Acute Restraint Stress Are Segregated within the Lateral Septal Area of Rats

Background: The Lateral Septal Area (LSA) is involved with autonomic and behavior responses associated to stress. In rats, acute restraint (RS) is an unavoidable stress situation that causes autonomic (body temperature, mean arterial pressure (MAP) and heart rate (HR) increases) and behavioral (increased anxiety-like behavior) changes in rats. The LSA is one of several brain regions that have been involved in stress responses. The aim of the present study was to investigate if the neurotransmission blockade in the LSA would interfere in the autonomic and behavioral changes induced by RS. Methodology/Principal Findings: Male Wistar rats with bilateral cannulae aimed at the LSA, an intra-abdominal datalogger (for recording internal body temperature), and an implanted catheter into the femoral artery (for recording and cardiovascular parameters) were used. They received bilateral microinjections of the non-selective synapse blocker cobalt chloride (CoCl2, 1 mM / 100 nL) or vehicle 10 min before RS session. The tail temperature was measured by an infrared thermal imager during the session. Twenty-four h after the RS session the rats were tested in the elevated plus maze (EPM). Conclusions/Significance: Inhibition of LSA neurotransmission reduced the MAP and HR increases observed during RS. However, no changes were observed in the decrease in skin temperature and increase in internal body temperature observed during this period. Also, LSA inhibition did not change the anxiogenic effect induced by RS observed 24 h later in the EPM. The present results suggest that LSA neurotransmission is involved in the cardiovascular but not the temperatur

Behavioral and Neurochemical Assessment of Parathyroid Hormone 2 (PTH2) Receptor Agonist Tuberoinfundibular Peptide of 39 (TIP39) in Neurological Disorders

The Objective of the present study is to elucidate the neuroendocrine role of TIP39 peptide in anxiety, depression and memory model with respect to the behavioural, neurochemical, gene expression and morphological changes in rats. In normal rats, ICV administration of TIP39 did not alter the behaviour, physiology and morphology demonstrating that administration TIP39 peptide did not influence the anxiety, depression and memory markers during the normal state. From the interactive study, PTH2R antagonist was used to study the role of TIP39 in ARS model; TIP39 significantly increased the NA and GABA release and significantly decreased the glutamate and CORT level in brain and plasma of ARS rats. This was reversed after PTH2R antagonist administration, indicating that TIP39 has direct role on noradrenergic, glutaminergic/GABAergic and HPA axis system through PTH2 receptor. CUMS rats exhibited significant reduction in sucrose intake, is a potential predictor of depressive state, led to cause energy deprivation, HPA axis abnormality, oxidative damage and inflammation. In this line, TIP39 both the doses (1 nmol & 10 nmol) effectively reversed the CUMS induced abnormalities. In addition to that, TIP39 effectively increased the GAD enzyme activity and decreased the acetyl cholinesterase activity in CUMS rats. CUMS induced abnormality in mineralocorticoid (MR) and glucocorticoid receptor (GR) gene expressions were significantly reversed after TIP39 administration. Moreover, TIP39 both the doses effectively improved the CUMS induced neurodegeneration in hippocampus and prefrontal cortex region. IMPACT OF THE STUDY: In this study, we found that TIP39 was acting through neurological and endocrinological pathway (bi-directionally) during the stressful condition; which is novel and unique to this study. Because of many existing therapies in the treatment of stress exhibited unidirectional approach which was not satisfactory still, since because stress is generated by both brain and endocrine system. Moreover, TIP39 did not produce any effect in normal state and it is involved only in pathological condition, hence clinically it can be used as a diagnostic marker in the treatment of stress and stress associated disorders

A study of the WKY as a rat model of depression

Includes bibliographical referencesMajor depression is a heterogeneous neuropsychiatric disorder with a significant genetic - stress interaction. The Wistar - Kyoto (WKY) rat displays hypersensitivity to stress and depression - like behaviour and is used as a genetic model of major depression. However, the depression - and anxiety - like behaviour of WKY has not yet been compared between the WKY/NCrl and WKY/NHsd substrains when characterizing WKY as a rat model of depression. WKY rats respond to noradrenergic and dopaminergic drugs but not to selective serotonin reuptake inhibitors (SSRIs) and are therefore suggested to model treatment resistant depression. The early life stress of maternal separation (MS) has been used to produce a rodent model of depression in Sprague - Dawley (SD) rats but results have been variable. It was therefore considered that WKY subjected to MS might produce a more robust model of depression than either WKY or MS alone. The widely used MS SD rat model of depression, as well as MS SD rats subjected to restraint stress in adult life, were evaluated as appropriate comparator models of depression. Furthermore, changes in the biochemistry in relevant brain areas of MS SD rats exposed to restraint stress in adulthood is still elusive and was further explored. The glutamate N - methyl - D - aspartate (NMDA) receptor antagonist, ketamine, has been found to be clinically useful. The acute effects of ketamine have not been previously tested in male WKY or MS SD rats and it was therefore decided to study the behavioural effects of ketamine in these rat models of depression. The aim of the first study was to characterize the WKY rat model of depression and to select the appropriate substrain of WKY best suited as a model of depression. The WKY/NCrl and WKY/NHsd substrains of WKY were tested for optimal depression - /anxiety - like behaviour in the forced swim test (FST), open field test (OFT) and elevated plus maze (EPM) and compared to the Wistar reference strain. Both WKY/NCrl and WKY/NHsd were less active than Wistar rats in the OFT and FST and WKY/NCrl were les s activ e than WKY/ NHsd. Therefore, the initial study identified WKY/NCrl as the appropriate substrain of WKY to model depression. The WKY/NCrl rats were further characterized in terms of their response to an optimal dose of the antidepressant drug, desipramine in the FST. Desipramine has been shown to be effective in reducing the depression - like behaviour of WKY and was therefore chosen as the antidepressant drug for this study. A dose of 15 mg/kg desipramine attenuated the depression - like behaviour as evide nced by decreased immobility in the FST and was therefore used for subsequent experiments. Desipramine had no effect on opioid receptors (μ - and κ - opioid receptors, MOR and KOR, respectively) , and tyrosine hydroxylase in the nucleus accumbens ( NAc ) or prefrontal cortex ( PFC ) of WKY rats

Behavioural, neurochemical and neuroendocrine effects of predator stress in mice

Stress plays a role in the etiology of anxiety and mood disorders. To investigate these disorders, animal models are used, many of which incorporate a stressful stimulus. Especially psychological stressors may resemble stressful situations that in humans can lead to pathology. The study, described in this thesis, was undertaken to elucidate the effects the psychological stressor predator exposure has on behaviour, on neurochemical parameters in various brain regions and on neuroendocrine parameters in mice. Therefore mice of several strains were exposed to a rat. Also the effects of repeated predator exposure were assessed. Rat exposure lead to risk assessment behaviour, followed by coping strategies. Extracellular levels of serotonin and its metabolite were higher than baseline levels in the hippocampus, prefrontal cortex, lateral septum, but not in the caudate putamen. Also the levels of noradrenaline were clearly increased in the hippocampus. Plasma concentrations of ACTH and corticosterone were mildly elevated in three out of five examined strains. These strains also exhibited a slightly different behavioural profile. With re-exposure, less risk assessment took place, levels of free corticosterone were lower, but hardly any differences in neurochemical parameters were seen. Taken together, behavioural, neurochemical and neuroendocrine parameters form a complimentary picture indicating that rat exposure in its current form had mild arousing properties. Also in this mild form predator exposure elicited a selective activation of brain regions and neurochemicals. This highly differentiated response may be of utmost importance to coordinate and to fine-tune the specific neuroendocrine, behavioural and autonomic responses to this form of stress. It might be worthwhile to increase the stressful properties of the paradigm to further look into these mechanisms.Stress spielt eine wichtige Rolle in der Ätiologie von Angsterkrankungen wie auch von affektiven Störungen. Um diese Erkrankungen zu erforschen werden Tierverhaltensmodelle genutzt, die meist auf der Verwendung stressvoller Stimuli beruhen. Im besonderen psychologische Stressoren könnten ein gutes Model für Situationen darstellen, die für Menschen pathologische Folgen haben können. Die vorliegende Arbeit beschreibt die Effekte des psychologischen Stressors Fressfeind-Exposition auf das Verhalten, neurochemische Parameter in unterschiedlichen Gehirnregionen und neuroendokrine Parameter in Mäusen. Hierzu wurden Mäuse unterschiedlicher Stämme einer Ratte ausgesetzt. Auch wurden die Effekte von wiederholter Exposition betrachtet. Rattenexposition führte zu Risikoabschätzungsverhalten gefolgt von Stressbewältigungsstrategien. Gleichzeitig waren die extrazellulären Werte von Serotonin und dessen Metabolit höher als unter Basalbedingungen im Hippocampus, präfrontalen Cortex und lateralen Septum aber nicht im Nucleus Caudatus des Putamen. Auch stieg Noradrenalin im Hippocampus deutlich an. In drei von fünf untersuchten Stämmen waren die Plasmakonzentrationen von ACTH und Corticosteron leicht erhöht. Diese Stämme zeigten auch ein anderes Verhaltensprofil. Bei wiederholter Exposition zeigten die Tiere weniger Risikoabschätzungsverhalten, niedrigere Konzentrationen freien Corticosterons, aber kaum Unterschiede in neurochemischen Parametern. Zusammengenommen formen die Verhaltens-, neurochemischen und neuroendokrinen Parameter ein sich ergänzendes Bild, woraus hervor geht, dass Rattenexposition leicht erregende Eigenschaften hatte. In der hier angewendeten milden Form verursachte Rattenexposition eine ausgeprägte und selektive Aktivierung von Gehirnregionen und Neurotransmittern. Diese hochdifferenzierte Antwort könnte von großem Belang für die Koordination der spezifischen neuroendokrinen, verhaltensbezogenen und autonomen Antworten auf diese Art Stress sein. Von Interesse wäre es in diesem Kontext die Intensität des Stressstimulus zu erhöhen, um diese Zusammenhänge und Mechanismen noch eingehender erforschen zu können

Development and use of "stress" animal models of depression to study the mode of action of antidepressant drug treatments

The effect of the exposure of male BALB/c mice to sensory stimuli from male Brown Norway rats was assessed using plasma corticosterone (CORT) concentrations and glucocorticoid receptor (GR) binding in the cortex, and a number of behavioural measures (sucrose preference, food intake and elevated plus-maze tests). Following 8 weeks of exposure, stressed mice showed a 97% increase in plasma CORT concentrations but GR binding, sucrose preference, food intake, and the elevated plus maze (EPM) measurements were unaltered. In conclusion, this study suggests that chronic exposure of mice to sensory stimuli from rats increases stress hormones and may provide a natural predator model of stress. The effects of acute and chronic restraint stress with the administration of paroxetine (10 mg/kg p. o.), a selective serotonin reuptake inhibitor (SSRI), on the hypothalamic-pituitary-adrenocortical (HPA) axis were studied in adult male Wistar rats. Three weeks of restraint stress induced a 700% increase in plasma CORT and a 100% increase in adrenocorticotrophin (ACTH) concentration, whilst decreasing GR binding in the cortex by 34% and hippocampus by 30%, and a 24% decrease in food intake. Administration of paroxetine induced a 166% increase in plasma CORT concentration, whilst decreasing GR mRNA levels by 45% in the cortex and food intake by 25%. Paroxetine administration decreased the stress-induced plasma CORT by 80% but enhanced ACTH concentration by 78%, partially reversing the stress-induced downregulation of GR in the cortex by 34%, increasing GR mRNA in the cortex by 58%, reducing BDNF mRNA in the cortex by 30%, and reversed the stress-induced decrease in food intake by 22%. Taken together, these results suggest that restraint stress provoked a stress response, which remained elevated after three weeks, and feedback inhibition on the HPA axis following stress was facilitated by treatment with paroxetine

The dual hit hypothesis of schizophrenia:evidence from animal models

Schizophrenia is a heterogeneous psychiatric disorder, which can severely impact social and professional functioning. Epidemiological and clinical studies show that schizophrenia has a multifactorial aetiology comprising genetic and environmental risk factors. Although several risk factors have been identified, it is still not clear how they result in schizophrenia. This knowledge gap, however, can be investigated in animal studies. In this review, we summarise animal studies regarding molecular and cellular mechanisms through which genetic and environmental factors may affect brain development, ultimately causing schizophrenia. Preclinical studies suggest that early environmental risk factors can affect the immune, GABAergic, glutamatergic, or dopaminergic system and thus increase the susceptibility to another risk factor later in life. A second insult, like social isolation, stress, or drug abuse, can further disrupt these systems and the interactions between them, leading to behavioural abnormalities. Surprisingly, first insults like maternal infection and early maternal separation can also have protective effects. Single gene mutations associated with schizophrenia did not have a major impact on the susceptibility to subsequent environmental hits

Glycogen Synthase Kinase-3β: An Investigation Of The Novel Serine 389 Phosphorylation Site

Stress associated psychiatric disorders such as depression, anxiety, and post-traumatic stress disorder affect a large proportion of the population. Reductions in the complexity of neuronal morphology and reduced neurogenesis are commonly observed outcomes following stress exposure in rodent models and may represent a mechanism for the reduced brain volume in stress sensitive regions such as the hippocampus observed in individuals diagnosed with stress associated disorders. Multiple lines of evidence suggest that glycogen synthase kinase (GSK)-B may play a role in the neurodegenerative phenotype observed following stress exposure. GSK3B is atypical in that it is inhibited by phosphorylation. This inhibitory phosphorylation has typically been studied by examining the phosphorylation state of the serine 9 (S9) site. Inhibition of GSK3B is implicated in synaptic stabilization, increased expression of trophic factors that support dendritic complexity and neurogenesis, reduced apoptosis, and the antidepressive effects of currently implemented therapeutics. It is surprising then that little research has examined the regulation of GSK3B by stress. A novel GSK3B phosphorylation site, serine 389 (S389), has recently been described that is regulated by p38 mitogen activated protein kinase (MAPK) and is independent of S9 phosphorylation by AKT. p38 MAPK is implicated in the behavioral effects of stress exposure making an understanding of its interaction with GSK3B S389 phosphorylation during stress a compelling research target. The current studies examine GSK3B regulation following variate stress exposure in stress reactive brain regions, describe the anatomical specificity of GSK3B S389 phosphorylation in the brain, and detail the behavioral phenotype of a novel mutant mouse that cannot inhibit GSK3B by S389 phosphorylation (GSK3B KI). Region specific changes in GSK3B phosphorylation were observed following stress exposure, as well as voluntary exercise, a behavior that confers stress resistance. Elevated GSK3B S389 phosphorylation was associated with increased levels of phosphorylated p38 MAPK. This pathway is implicated in the response to DNA damage, and, surprisingly, we observed that histone H2A-variant-X (H2A.X), a marker of DNA damage, was elevated following stress and exercise. Accumulated DNA damage is a proposed driver of neurodegeneration suggesting that the pathway activated by stress may be engaged to protect against such decline. Consistent with a role in the response to DNA damage, we observed a primarily nuclear localization of GSK3B S389 phosphorylation in the brain while S9 phosphorylation was found in nuclear and cytosolic compartments. Further, we observed neurodegeneration in hippocampal and cortical regions of GSK3B KI mice supporting the idea that the inhibition of GSK3B by S389 phosphorylation observed following stress and exercise may be protective. Though largely similar to wild type mice in behavioral tests, increased auditory fear conditioning was evident in GSK3B KI mice. Contextual and cued freezing was prolonged in GSK3B KI mice, a phenotype that is commonly observed in stress models. Together these findings suggest that GSK3B S389 phosphorylation is playing a critical role in neuronal integrity that is independent of GSK3B S9 phosphorylation, and that the subset of neurons protected by GSK3B S389 phosphorylation may play an important role in preventing a portion of the maladaptive behavioral changes observed following stress exposure

Serotonin Modulates the Maturation of the Medial Prefrontal Cortex and Hippocampus: Relevance to the Etiology of Emotional and Cognitive Behaviors

Increasing evidence suggests that anxiety and depression disorders have neurodevelopmental roots, with a strong case for early-life serotonergic dysfunction in their ontogeny. For instance, disrupting serotonergic tone during critical developmental periods results in dysregulated adult affective behaviors, in mice. However, insight into the mechanism by which early-life serotonin levels impact emotional behaviors in later-life, remains scarce. Based on its potent neurotrophic properties, we hypothesized that serotonin acts during development to guide the maturation of brain regions implicated in the modulation of both the emotional and cognitive features of anxiety and depression disorders, namely the medial prefrontal cortex (mPFC) and hippocampus (HC). To address this hypothesis, we employed a pharmacological mouse model in which serotonin levels were increased using a selective serotonin reuptake inhibitor, fluoxetine (FLX), during a previously established critical post-natal time window (post-natal day 2-11; "PN-FLX" mouse model). The effect of this post-natal serotonergic disruption on the structural, physiological and functional properties of the adult mPFC and HC was assessed. In the mPFC, we found morphological and electrophysiological changes specific to cortical layer 2/3. Pyramidal neurons in layer 2/3 of the infralimbic (IL) sub-region of the mPFC, displayed decreased dendritic arborization, concomitant with reduced intrinsic excitability. Conversely, prelimbic (PL) layer 2/3 neurons displayed normal dendritic arborization, but increased intrinsic excitability. Together, these changes produce a reduced IL/PL output ratio. In order to probe the functional consequences of these changes, we investigated the ability of PN-FLX mice to extinguish learned fear ("fear extinction"), as performance in this behavioral paradigm is modulated by IL/PL output. Congruent with their altered IL/PL balance, PN-FLX mice display deficits in fear extinction learning and recall. Mimicking the diminished IL/PL ratio by selectively lesioning the IL, in control mice, phenocopied some features of the PN-FLX anxiety and depression-behavioral profile, demonstrating a causal relationship between mPFC changes and the emotional phenotype of PN-FLX mice. In the HC, PN-FLX treatment produced retraction of dendritic arbors but increased branching in the cornu ammonis 3 (CA3) sub-field. PN-FLX treatment also reduced total synapse number and synaptic density of CA3 neurons. In order to probe the functional consequences of these morphological changes, we investigated spatial learning in the Morris water maze and contextual fear conditioning in PN-FLX mice, as these behaviors are sensitive to CA3 manipulations. In line with reduced CA3 function, PN-FLX mice displayed deficits in both these learning paradigms. Taken together, our findings demonstrate that serotonin acts during a key developmental epoch to set the structural and physiological properties, and ultimately the functional output, of two key brain regions that underlie affective and cognitive behaviors, the mPFC and HC. Our findings provide a mechanism by which reported genetic (polymorphisms, mutations) and environmental factors (exposure to pharmacological agents or stress) that alter serotonergic tone during development, have long-term, often indelible, consequences on adult affective and cognitive function