Restraint Stress In Rats Research Articles

Role of CRF1 and CRF2 receptors in the lateral hypothalamus in anxiogenic response evoked by acute and repeated restraint stress in rats

The lateral hypothalamus (LH) is an important hypothalamic area that has been implicated in the integration of behavioral and physiological responses to stress. The corticotropin‐releasing factor (CRF) system has been shown to be an important neurochemical mechanism in the central nervous system involved in the etiology of the behavioral changes evoked by exposure to aversive situations. The exposure to chronic stress affects the expression of CRF neurotransmission components in brain regions controlling stress responses. However, the role of CRF neurotransmission within the LH in the anxiogenic responses evoked by acute and repeated restraint stress (RS) has not been investigated. Here, was investigated the effect of bilateral microinjection into the LH of the selective CRF1 receptor antagonist CP376395 or the selective CRF2 receptor antagonist antisauvagine‐30 (ASV‐30) in the anxiogenic responses following the first and the 10th session of restraint stress (RS) in male rats. For this, male Wistar rats (250g) had cannula‐guide bilaterally implanted within the LH. The RS was realized by placing the animals in a plastic cylindrical tube for 60 minutes. Independent sets of animals received CP376395 (0.01 mol/100nL), ASV‐30 (0.01 mol/100nL) or vehicle into the LH 10 minutes before the onset of the first or 10th session of RS. Immediately after the end of the stress session, the animals were individually placed in the elevated plus maze (EPM) for 5 minutes to assess anxiety‐related behaviors. The behavioral analysis revealed that an acute RS session decreased the % of entries and time in the open arms of the EPM in vehicle‐treated animals, when compared to animals that were not submitted to restraint stress (i.e., naïve group) (P<0.05). Bilateral microinjection of either CP376395 or ASV‐30 into the LH inhibited the decreased open‐arms exploration caused by acute restraint stress (P<0.05). We did not identify behavioral changes in the EPM in animals repeatedly subjected to restraint stress, and pharmacological treatments also had no behavioral effect when administered before the 10th RS session (P>0.05). Taken together, the results indicates that the CRFergic neurotransmission in the LH, acting through activation of both CRF1 and CRF2 receptors, is involved in the generation of anxiety‐like behaviors induced by acute restraint stress, and the previous repeated exposure to this stressor affect this control.

Role of CRF1 and CRF2 receptors in the lateral hypothalamus in cardiovascular and anxiogenic responses evoked by restraint stress in rats: Evaluation of acute and chronic exposure

We investigated the role of corticotropin-releasing factor (CRF) neurotransmission within the lateral hypothalamus (LH) in cardiovascular and anxiogenic-like responses evoked by acute and repeated restraint stress in rats. For this, animals were subjected to intra-LH microinjection of a selective CRF1 (CP376395) or CRF2 (antisauvagine-30) receptor antagonist before either an acute or the 10th session of restraint stress. Restraint-evoked arterial pressure and heart rate increases, tail skin temperature decrease and anxiogenic-like effect in the elevated plus maze (EPM) were evaluated. We also assessed the effect of 10 daily sessions of restraint on expression of CRF1 and CRF2 receptors within the LH. We identified that antagonism of either CRF1 or CRF2 receptor within the LH decreased the tachycardia during both the acute and 10th session of restraint, but the effect of the CRF1 receptor antagonist was more pronounced during the 10th session. Acute restraint stress also caused anxiogenic-like effect, and this response was inhibited in animals treated with either CP376395 or antisauvagine-30. Anxiety-like behaviors were not changed following the 10th session of restraint, and pharmacological treatments did not affect the behavior in the EPM in chronically stressed animals. Repeated restraint also did not change the level of the CRF receptors within the LH. Taken together, the findings indicate that CRF1 and CRF2 receptors within the LH are involved in tachycardic and anxiogenic-like responses to aversive stimuli. Control of tachycardia by the CRF1 receptor is sensitized by previous stressful experience, and this effect seems to be independent of changes in expression of the receptor.

Curcumin alleviates restraint stress-induced learning and memory deficit and activity via modulation of biochemical, morphology changes, and apoptosis in the prefrontal cortex and hippocampus.

Restraint stress indicated induction of morphology, biochemistry, and behavioral impairments. Several investigations have reported that curcumin has a protective effect against stress disturbance. The present study is designed to investigate the effects of curcumin on learning and memory, activity, biochemical, morphology changes, and apoptosis in the hippocampus and prefrontal cortex of restraint stress rats. For chronic restraint stress, the rats were kept in the restrainers for 2.5 h per day for 21 consecutive days. The animals received the gavage of curcumin every other day for 21 days. After stress, the animals were subjected to behavioral tests. In restraint stress rats, locomotor activity and step-through latency were decreased using open field and shuttle box, respectively. Then, the rats were sacrificed to assess their serum and brains. A reduction was seen in the serum malonedialdehyde levels and number of neurons in the hippocampus and prefrontal cortex. The significantly decreased serum total antioxidant capacity levels and increased apoptotic cells were observed in the hippocampus and prefrontal cortex. Finally, curcumin inhibited and reversed the changes of stress induced in the prefrontal cortex and hippocampus of the rats. These findings provided evidence for the protective effect of curcumin therapy on biochemical, morphology, and behavioral changes induced by restraint stress. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

The dual gastro- and neuroprotective effects of curcumin loaded chitosan nanoparticles against cold restraint stress in rats

Stress is a condition affecting different body systems. Curcumin (CUR) is a natural compound that has various pharmacological benefits. However, its poor oral bioavailability limits its therapeutic value. This study aimed to formulating curcumin loaded chitosan nanoparticles (CS.CUR.NPs) and investigate its gastroprotective and neuroprotective effects in rats subjected to cold restraint stress (CRS), in reference to conventional oral CUR preparation, and explore its underlying mechanism. Treated groups received either CUR or CS.CUR.NPs (100 mg∕kg) orally for 14 days before exposure to CRS. CRS elicited marked behavioral changes and gastric ulcer accompanied by histopathological abnormalities of the brain and stomach along with elevation of pain score. CUR and CS.CUR.NPs improved stress-induced gastric ulcer, cognitive performance, and pain sensation. Mechanistically, CRS disrupts oxidative and inflammatory status of the brain as manifested by high malondialdehyde and IL-6 and low total antioxidant capacity and IL-10, along with high C-reactive protein level. CRS decreased nuclear factor erythroid 2-related factor2 (Nrf2) and increased nuclear factor-kappa B (NF-κB) expressions. Furthermore, brain levels of unphosphorylated signal transducer and activator of transcription3 (U-STAT3) and glial fibrillary acidic protein (GFAP) were upregulated with stress. CUR and CS.CUR.NPs provided beneficial effects against harmful consequences resulting from stress with superior beneficial effects reported with CS.CUR.NPs. In conclusion, these findings shed light on the neuroprotective effect of CUR and CS.CUR.NPs against stress-induced neurobehavioral and neurochemical deficits and protection against stress-associated gastric ulcer. Moreover, we explored a potential crosslink between neuroinflammation, U-STAT3, NF-κB, and GFAP in brain dysfunction resulted from CRS.

Differential roles of prelimbic and infralimbic cholinergic neurotransmissions in control of cardiovascular responses to restraint stress in rats

Previous studies showed a prominent role of the medial prefrontal cortex (mPFC), especially the prelimbic (PL) and infralimbic (IL) subregions, in behavioral and physiological responses to stressful stimuli. Nevertheless, the local neurochemical mechanisms involved are not completely understood. In this sense, previous studies identified cholinergic terminals within the mPFC, and stressful stimuli increased local acetylcholine release. Despite these pieces of evidence, the specific role of cholinergic neurotransmission in different subregions of the mPFC controlling the cardiovascular responses to stress has never been systematically evaluated. Therefore, the purpose of this study was to investigate the involvement of cholinergic neurotransmission present within PL and IL in cardiovascular responses to an acute session of restraint stress in rats. For this, rats received bilateral microinjection of the choline uptake inhibitor hemicholinium-3 before exposure to restraint stress. The arterial pressure and heart rate (HR) increases and the decrease in tail skin temperature as an indirect measurement of sympathetically-mediated cutaneous vasoconstriction were recorded throughout the restraint stress session. The results showed that the depletion of acetylcholine within the PL caused by local microinjection of hemicholinium-3 decreased the tachycardia to restraint stress, but without affecting the pressor response and the drop in tail skin temperature. Conversely, IL treatment with hemicholinium-3 decreased the restraint-evoked pressor response and the sympathetically-mediated cutaneous vasoconstriction without interfering with the HR response. Taken together, these results indicate functional differences of cholinergic neurotransmission within the PL and IL in control of cardiovascular and autonomic responses to stressful stimuli.

Metformin improves bioenergetics state and mitochondrial dynamics of different brain regions in restraint stressed rats

Mitochondrial dysfunction contribute to ageing and neurodegenerative disorders by producing reactive oxygen species (ROS). Restraint stress as a physical and psychological stressor results in increased generation of ROS, selectively affects the hippocampal neurons that associated with an impairment in spatial learning and memory tasks. Metformin activates AMP-activated protein kinase (AMPK) that presents anti-inflammatory and anti-oxidative properties on the human brain metabolism. Here, we aimed to investigate the adverse effects of restraint stress on the mitochondrial functions of central nervous system which would be attenuated by metformin.

Kamikihito rescued depressive-like behaviors and hippocampus neurogenesis in chronic restraint stress rats

Background and aimSubstantial evidence suggests the effectiveness of plant-based medicine in stress-related diseases. Kamikihito (KKT), a Japanese traditional herbal medicine (Kampo), has been used for anemia, insomnia, and anxiety. Recent studies revealed its ameliorating effect on cognitive and memory dysfunction in several animal models. We, therefore, determined whether daily supplementation of KKT has an antidepressant-like effect on the stress-induced behavioral and neurological changes in rats. Experimental procedureThe effect of KKT against the stress-induced changes in anxiety- and depressive-like behaviors and hippocampal neurogenesis were determined using a rat model of chronic restraint stress (CRS). KKT was orally administered daily at 300 or 1000 mg/kg during 21 consecutive days of CRS (6 h/day). The effect of CRS and KKT on physiological parameters, including body weight gain, food/water consumptions, plasma corticosterone (CORT) levels, and percentage of adrenal gland weight to body weight, were firstly measured. Anxiety- and depressive-like behaviors in rats were assessed in the open field test (OFT), sucrose preference test (SPT), and forced swimming test (FST). Hippocampal neurogenesis was determined by immunohistochemistry. Results and conclusionCRS for 21 days caused a significant decrease in body weight gain and increase in plasma CORT levels and percentage of adrenal gland weight to body weight, which were rescued by KKT treatment. KKT also suppressed the CRS-induced anxiety- and depressive-like behaviors and impairment of hippocampal neurogenesis. These results suggest that daily treatment of KKT has a protective effect against physiological, neurological, and behavioral changes in a rat model of depression.

Optimized Tibial Nerve Stimulation Partially Reduces Visceral Hypersensitivity in Rats Mediated via Autonomic and Opioid Mechanisms

The aim of this study was to investigate the therapeutic effect and possible mechanisms of tibial nerve stimulation (TNS) on visceral hypersensitivity in rats. 1) The effects of TNS with five sets of parameters on visceral sensitivity in normal rats were evaluated by the assessment of abdominal electromyogram (EMG) and abdominal withdrawal reflex (AWR). 2) The effects and mechanisms of TNS with a special set of parameters (14Hz, 330 μsec, and 40% motor threshold) were evaluated in acute visceral hypersensitivity rats induced by restraint stress and colonic hypersensitized rats induced by acetic acid during the neonatal stage assessed by the EMG, AWR, and the spectral analysis of heart rate variability derived from the electrocardiogram. 1) In normal rats, TNS did not show any effect on the visceromotor reflex. 2) In rats with restraint stress-induced hypersensitivity, TNS with the special set of parameters reduced AWR scores and EMG responses to rectal distention at a pressure of 20-60 mmHg (p < 0.05, vs. baseline for both AWR and EMG). Concurrently, TNS increased vagal activity and decreased sympathetic activity (p < 0.03 for both). 3) Similar effects were noted on the EMG (p < 0.05, vs. baseline) and AWR (p < 0.05 vs. baseline) with acute and chronic TNS in rats with chronic colonic hypersensitivity and the effects were blocked by naloxone. TNS with parameters of 14Hz, 330 μsec, and 40% motor threshold is effective in improving visceral hypersensitivity in rodent models of colonic hypersensitivity via the modulation of autonomic and opioid mechanisms.

Orexin 2 receptor in the nucleus accumbens is critical for the modulation of acute stress-induced anxiety

Orexin is a neuropeptide mainly synthesized in the lateral hypothalamus/perifornical area and has been traditionally implicated in feeding, sleep-wake cycles, and reward. Intriguingly, patients with anxiety have increased levels of orexin in the cerebrospinal fluid. Pharmacological or genetic manipulation of orexin receptors affects anxiety-like behaviors in rodents, suggesting an involvement of the orexin signaling in the regulation of anxiety. Yet, the neural substrates involved remain largely unknown. The nucleus accumbens (NAc) shell holds a key position in the modulation of anxiety-related behaviors. Therefore, in the present study, by using neuropharmacology, molecular approaches and behavioral tests in rats, the role of orexin/orexin receptors in the NAc shell on the anxiety-like behaviors was investigated. We found that microinjection of orexin-A into the NAc shell induced an anxiogenic-like effect. Quantitative real-time PCR and immunofluorescence showed that the orexin 2 receptor (OX2R) is expressed and distributed in the NAc shell neurons. Activation of OX2R mimicked the anxiogenic effect of orexin-A. Moreover, infusion of an OX2R antagonist had no effect on anxiety-like behaviors in normal rats, but reversed anxiogenic effect induced by acute restraint stress. Finally, we found that downregulation of OX2R in the NAc shell caused an anxiolytic-like effect in acute restraint stressed rats, which was consistent with the pharmacological results. Together, this study suggests that OX2R in the NAc shell is involved in the regulation of acute stress-induced anxiety, and raises the possibility that OX2R antagonist may serve as an effective mean to treat anxiety disorders.

Angiotensinergic Neurotransmissions in the Medial Amygdala Nucleus Modulate Behavioral Changes in the Forced Swimming Test Evoked by Acute Restraint Stress in Rats.

We investigated the role of angiotensin II type 1 (AT1 receptor) and type 2 (AT2 receptor) and MAS receptors present in the medial amygdaloid nucleus (MeA) in behavioral changes in the forced swimming test (FST) evoked by acute restraint stress in male rats. For this, rats received bilateral microinjection of either the selective AT1 receptor antagonist losartan, the selective AT2 receptor antagonist PD123319, the selective MAS receptor antagonist A-779, or vehicle 10 min before a 60 min restraint session. Then, behavior in the FST was evaluated immediately after the restraint (15 min session) and 24 h later (5 min session). The behavior in the FST of a non-stressed group was also evaluated. We observed that acute restraint stress decreased immobility during both sessions of the FST in animals treated with vehicle in the MeA. The decreased immobility during the first session was inhibited by intra-MeA administration of PD123319, whereas the effect during the second session was not identified in animals treated with A-779 into the MeA. Microinjection of PD123319 into the MeA also affected the pattern of active behaviors (i.e., swimming and climbing) during the second session of the FST. Taken together, these results indicate an involvement of angiotensinergic neurotransmissions within the MeA in behavioral changes in the FST evoked by stress.

A functional selective effect of oxytocin secreted under restraint stress in rats

Restraint stress (RS) is an unavoidable stress model that triggers activation of the autonomic nervous system, endocrine activity, and behavioral changes in rodents. Furthermore, RS induces secretion of oxytocin into the bloodstream, indicating a possible physiological role in the stress response in this model. The presence of oxytocin receptors in vessels and heart favors this possible idea. However, the role of oxytocin secreted in RS and effects on the cardiovascular system are still unclear. The aim of this study was to analyze the influence of oxytocin on cardiovascular effects during RS sessions. Rats were subjected to pharmacological (blockade of either oxytocin, vasopressin, or muscarinic receptors) or surgical (hypophysectomy or sinoaortic denervation) approaches to study the functional role of oxytocin and its receptor during RS. Plasma levels of oxytocin and vasopressin were measured after RS. RS increased arterial pressure, heart rate, and plasma oxytocin content, but not vasopressin. Treatment with atosiban (a Gi biased agonist) inhibited restraint-evoked tachycardia without affecting blood pressure. However, this effect was no longer observed after sinoaortic denervation, homatropine (M2 muscarinic antagonist) treatment or hypophysectomy, indicating that parasympathetic activation mediated by oxytocin secreted to the periphery is responsible for blocking the increase in tachycardic responses observed in the atosiban-treated group. Corroborating this, L-368,899 (oxytocin antagonist) treatment showed an opposite effect to atosiban, increasing tachycardic responses to restraint. Thus, this provides evidence that oxytocin secreted to the periphery attenuates tachycardic responses evoked by restraint via increased parasympathetic activity, promoting cardioprotection by reducing the stress-evoked heart rate increase.

Spleen tissue changes after restraint stress: effects of aerobic exercise training

Inflammation has been described as a prominent mechanism involved in dysfunctions and diseases evoked by chronic stress. Notably, the spleen is an immune organ controlled by sympathetic and glucocorticoid mechanisms, but the impact of chronic stress in the spleen is not entirely understood. Besides, the impact of aerobic exercise training on the effects of chronic stress in the spleen has never been reported. Therefore, this study aimed to assess the changes caused in the spleen by repeated restraint stress and the effect of aerobic exercise training performed after a period of chronic restraint stress in rats. We identified that daily exposure to restraint stress (120 min per session, for 14 consecutive days) increased corticosterone and noradrenaline content, gene expression of glucocorticoid and β2-adrenergic receptors, TNF-α and IL-6 levels, and increased pro-oxidant substances in the spleen. Circulating levels of corticosterone were also increased in chronically stressed animals. Exercise training (1 h a day/5 days per week, for 60 days) increased glucocorticoid receptor gene expression, interleukin (IL)-10 and antioxidant mechanisms in the spleen. Exercise also decreased splenic noradrenaline, tumoral necrosis factor (TNF)-α, and IL-6 contents. Lastly, the effects of repeated restraint stress in the spleen were mitigated in animals subjected to aerobic training. Taken together, the results reported in the present study indicate that aerobic exercise training is a relevant non-pharmacological therapeutic approach to dysfunctions in the spleen caused by a period of stress.

Nitric Oxide in the Spinal Cord Is Involved in the Hyperalgesia Induced by Tetrahydrobiopterin in Chronic Restraint Stress Rats.

It has been well recognized that exposure to chronic stress could increase pain responding and exacerbate pain symptoms, resulting in stress-induced hyperalgesia. However, the mechanisms underlying stress-induced hyperalgesia are not yet fully elucidated. To this end, we observed that restraint as a stressful event exacerbated mechanical and thermal hyperalgesia, accompanied with up-regulation of nitric oxide (NO) (P < 0.001), GTP cyclohydrolase 1 (GCH1) (GCH1 mRNA: P = 0.001; GCH1 protein: P = 0.001), and tetrahydrobiopterin (BH4) concentration (plasma BH4: P < 0.001; spinal BH4: P < 0.001) on Day 7 in restraint stress (RS) rats. Intrathecal injection of Nω-nitro-L-arginine methyl ester (L-NAME), a non-specific NO synthase inhibitor, or N-([3-(aminomethyl)phenyl]methyl) ethanimidamide, a special inhibitor of inducible NO synthase (iNOS), for seven consecutive days attenuated stress-induced hyperalgesia and decreased the production of NO (P < 0.001). Interestingly, 7-nitro indazole, a special inhibitor of neuronal NO synthase, alleviated stress-induced hyperalgesia but did not affect spinal NO synthesis. Furthermore, intrathecal injection of BH4 not only aggravated stress-induced hyperalgesia but also up-regulated the expression of spinal iNOS (iNOS mRNA: P = 0.015; iNOS protein: P < 0.001) and NO production (P < 0.001). These findings suggest that hyperalgesia induced by RS is associated with the modulation of the GCH1–BH4 system and constitutively expressed spinal iNOS. Thus, the GCH1–BH4–iNOS signaling pathway may be a new novel therapeutic target for pain relief in the spinal cord.

Interval aerobic training improves bioenergetics state and mitochondrial dynamics of different brain regions in restraint stressed rats.

Evidence has validated the prophylactic effects of exercising on different aspects of health. On the opposite side, immobilization may lead to various destructive effects causing neurodegeneration. Here, we investigated the association between exercising and mitochondrial quality for preventing the destructive effects of restraint stress in different rat brain regions. Twenty-four male Wistar rats, were randomized into four groups (n = 6), exercise, stress, exercise + stress, and control. The exercise procedure consisted of running on a rodent treadmill for 8weeks, and rats in the stress group were immobilized for 6h. Rats were then euthanized by decapitation and tricarboxylic acid (TCA) cycle enzyme activity, antioxidant levels, and mitochondrial biogenesis factors were assessed in the frontal, hippocampus, parietal and temporal regions using spectrophotometer and western blot technique. Based on our results, increased activity of TCA cycle enzymes in the exercised and exercise-stressed groups was detected, except for malate dehydrogenase which was decreased in exercise-stressed group, and fumarase that did not change. Furthermore, the level of antioxidant agents (superoxide dismutase and reduced glutathione), mitochondrial biogenesis factors (peroxisome proliferator-activated receptor gamma coactivator 1-alpha and mitochondrial transcription factor A), and dynamics markers (Mitofusin 2, dynamic related protein 1, PTEN induced putative kinase-1, and parkin) increased in both mentioned groups. Interestingly our results also revealed that the majority of the mitochondrial factors increased in the frontal and parietal lobes, which may be in relation with the location of motor and sensory areas. Exercise can be used as a prophylactic approach against bioenergetics and mitochondrial dysfunction.

The Effect of Ascorbic Acid and Selenium intake on serum Cortisol in rats Under Restraint Stress

Over the recent years ,vitamin C and selenium have been a clear line of defense against the effects of stress.The goal of the study is to indicate the effect of restraint stress in rats on the serum levels of cortisol, the roleof vitamin C and selenium supplement in stress relief by determining their effect on serum cortisol . fortyWistar rats were divided randomly into four equal groups (n=10), all the animal except negative controlexposed to restraint stress for six hours a day . the first group were supplemented with vitamin C in a doseof (50 mg/kg bw/day) orally, the second included given selenium in a dose of (0.02 µg/kg bw/day) orally,the control included ten rats . Blood was collected on 20th days, and serum cortisol were measured byenzyme-linked immunosorbent assay (ELISA). Results showed that supplement of rats with vitamin C hadhigh significant increasein serum cortisol in stressed rat (14.65 ± 5) compared to those with no stress (8.77± 4) which constitute the negative control . The study also revealed that supplement of rats with vitamin C ,Selenium and (vitamin C + Selenium) have highly significantly increased serum cortisol level to be (10.42 ±3.78), (10.29 ± 4.54) and (12.77 ± 3.57) respectively compared to stressed rats . It is concluded that chronicstress restriction can result in cumulative initiation of cortisol secretion in rats. Intake of vitamin C canrelieve stress by increasing decreasing cortisol .

Corticotropin-releasing factor neurotransmission in the lateral hypothalamus modulates the tachycardiac response during acute emotional stress in rats

The lateral hypothalamus (LH) is implicated in the physiological and behavioral responses during stressful events. However, the local neurochemical mechanisms related to control of stress responses by this hypothalamic area are not completely understood. Therefore, in this study we evaluated the involvement of CRFergic neurotransmission acting through the CRF1 receptor within the LH in cardiovascular responses evoked by an acute session of restraint stress in rats. For this, we investigated the effect of bilateral microinjection of different doses (0.01, 0.1 and 1 nmol/100 nL) of the selective CRF1 receptor antagonist CP376395 into the LH on arterial pressure and heart rate increases and decrease in tail skin temperature evoked by acute restraint stress. We found that all doses of the CRF1 receptor antagonist microinjected into the LH decreased the restraint-evoked tachycardia, but without affecting the arterial pressure and tail skin temperature responses. Additionally, treatment of the LH with CP376395 at the doses of 0.1 and 1 nmol/100 nL increased the basal values of both heart rate and arterial pressure, whereas the dose of 0.1 nmol/100 nL decreased the skin temperature. Taken together, these findings indicate that CRFergic neurotransmission in the LH, acting through activation of local CRF1 receptors, plays a facilitatory role in the tachycardia observed during aversive threats, but without affecting the pressor and tail skin temperature responses. Our results also provide evidence that LH CRFergic neurotransmission in involved in tonic maintenance of cardiovascular function.

Antidepressant-like effects of albiflorin involved the NO signaling pathway in rats model of chronic restraint stress.

The depressant-like effects of albiflorin (AF) were studied on stressed chronic restraint stress (CRS) rats. Experimental rats were subjected to immobilization stress for a daily 6 h-restraining in a plastic restrainer for continuous 21 d and were treated with 30 or 15 mg·kg-1 of AF for 21 d. Control rats were maintained in completely non stressed conditions. Behavioral tests and biochemical analysis were applied to investigating a regulatory mechanism of anti-stress of AF. Treatment with AF significantly restored the depressant-like behaviors. Besides, AF increased the levels of 5-hydroxytryptophan (5-HT), 5-hydroxyindoleacetic acid (5-HIAA), noradrenaline (NE) and dopamine (DA) in the hippocampus and increased the level of brain-derived neurotrophic factor (BDNF) in serum and protein expression in hippocampus. In addition, AF decreased the levels of hypothalamo-pituitary-adrenal (HPA) cascade, reduced the level of NO and cGMP in serum and inhibited the overexpression of 5-HT2AR mRNA and protein expression. Taken together, AF can modulate the NO-mediated network pathway in the hippocampus against stress-induced depressive-like behaviors. These physiological and behavioral changes allow rats to avoid potential deleterious effects of stress that may result from chronically elevated levels of glucocorticosteroids over days.

Changes in nitric oxide, carbon monoxide, hydrogen sulfide and male reproductive hormones in response to chronic restraint stress in rats

Gasotrasmitters are endogenously synthesized gaseous molecules that are engaged in cellular physiological and pathological processes. Stress influences various physiological aspects of an organism and amends a normal system's functions, including those of the reproductive system. This study aims to investigate the effect of long-term exposure to restraint stress on the male reproductive system as well as the possible impact of stress on the levels of nitric oxide (NO), carbon monoxide (CO) and hydrogen sulfide (H2S), and the expression of their producing-enzymes. In this study, rats were subjected to the restraint condition for 2 h per day and 7 days per week for 8 consecutive weeks. The results revealed decreases in the serum levels of kisspeptin-1(Kiss-1), gonadotropin-releasing hormone (GnRH), luteinizing hormone (LH), follicle stimulating hormone (FSH), testosterone and dehydroepiandrosterone sulfate (DHEA-s); however, corticosterone, gonadotropin-inhibitory hormone (GnIH), estradiol (E2) and prolactin levels increased following restraint stress. The mRNA expression levels of NO synthases (NOSs); neuronal NOS (nNOS), inducible NOS (iNOS) and H2S synthases; cystathionine-γ-lyase- (CSE), 3-mercaptopyruvate-sulfurtransferase- (3MST) and CO-producing enzyme; heme oxygenase-2 (HO-2) were upregulated in the hypothalamus of restraint rats. Testicular mRNA expression levels of endothelial NOS (eNOS), nNOS, HO-1 and HO-2 were upregulated whereas cystathionine β-synthase (CBS), CSE and 3MST expression levels were downregulated following restraint stress. Concentrations of NO increased in the testes but decreased in the semen of restraint rats. On the contrary, CO levels were reduced in the testes while they were elevated in the semen, whereas H2S concentrations decreased in both testes and semen of restraint rats. Concentrations of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX), as well as total antioxidant capacity (TAC) rose in the testes, while they declined in the semen of the restraint group. Restraint stress decreases the levels of reactive oxygen species (ROS) and malondialdehyde (MDA) in the testes while increasing them in the semen. Collectively, restraint stress negatively impacts male reproductive functions and modulates gasotransmitters producing-enzymes expression in the hypothalamus and testes.

The Synergistic Effect of Ascorbic Acid and Selenium on Serum Testosterone in Restraint Stressed Rats

The Synergistic Effect of Ascorbic Acid and Selenium on Serum Testosterone in Restraint Stressed Rats

Spontaneous recovery, time course, and circadian influence on habituation of the cardiovascular responses to repeated restraint stress in rats.

We investigated the spontaneous recovery, time course, and the influence of the time of day on the habituation of the cardiovascular responses with repeated exposure to restraint stress in male rats. Habituation of the corticosterone response to repeated restraint stress was also evaluated. The circulating corticosterone response decreased during both the stress and recovery periods of the tenth session of restraint. Habituation of the cardiovascular responses was identified as a faster return to baseline values of the heart rate (HR) and blood pressure (BP) during the recovery period of the tenth session of restraint. Habituation of the HR and BP was still observed after 10 days of discontinuation of the repeated exposure to restraint stress. However, spontaneous recovery of habituated responses was observed 20 days after the final restraint stress session. Time course analysis revealed decreased HR response during the recovery period of the third restraint session, without further reduction on the fifth, seventh, and tenth sessions. Decreased BP response was identified on the third and fifth sessions, whereas reduced tail skin temperature response was observed only on the fifth and seventh sessions. Regarding the time of day, habituation of the tachycardiac response was identified at the tenth session when repeated restraint stress was performed in the morning and night periods, but not in the afternoon. These findings provided evidence of spontaneous recovery of the habituation of cardiovascular responses to repeated restraint stress. Moreover, cardiovascular habituation was dependent on the number of trials and time of day.