Effects Of Forced Swim Stress Research Articles

Impact of Forced Swimming Stress on Serum Adiponectin and Endothelin-1 Levels in Wistar Rats: Comparative Analysis of Dietary Effects.

Aim This study aimed to assess the impact of forced repeated swimming stress on serum adiponectin and endothelin-1 levels in Wistar rats, comparing the effects between those fed a standard diet and those on a high-fat diet. Methods Twenty adult male Wistar rats were divided into two dietary groups: a standard food diet group (NFD, n=10) and a high-fat diet group (HFD, n=10). Both groups underwent daily forced swimming stress for six days, with durations increasing from 5 to 30 minutes. The protocol finished in an acute bout of swimming exercise on the seventh day with a duration of 40 minutes. Adherence to ethical guidelines was strictly maintained, and serum adiponectin and endothelin-1 levels were measured pre- and post-exercise using the ELISA method. Results Before swimming, the mean adiponectin levels were 4.30±1.50 ng/mL in the NFD group and 3.53±0.70 ng/mL in the HFD group. Post-exercise, these levels significantly decreased to 2.4±0.84 ng/mL (p=0.003) and 1.58±0.23 ng/mL (p=0.001), respectively. Endothelin-1 levels also showed significant decreases from 0.86 pg/mL (0.74-0.87) to 0.49 pg/mL (0.43-0.62) (p=0.003) in the NFD group, and from 0.89 pg/mL (0.86-0.93) to 0.69 pg/mL (0.60-0.75) (p=0.027) in the HFD group after swimming. Conclusion The study highlighted the significant effects of forced swimming stress on lowering serum adiponectin and endothelin-1 levels in Wistar rats, with more pronounced decreases observed in rats on a high-fat diet. The results of the study suggest the potential of exercise as a crucial component of strategies aimed at managing obesity and improving cardiovascular health, emphasizing the interaction between physical stress and dietary factors on metabolic and cardiovascular biomarkers.

Ventral hippocampal NMDA receptors mediate the effects of nicotine on stress-induced anxiety/exploratory behaviors in rats

Brief exposure to stress increases the tendency to drug abuse, especially cigarette smoking. It seems that nicotine abuse alleviates some psychological and physiological stress symptoms. The present study investigated the effect of nicotine administration on stress-induced anxiety-like behavior in adult male Wistar rats. Also, the possible role of the ventral hippocampal (VH) glutamatergic NMDA receptors was examined in the stress-induced anxiety-like behavior under nicotine administration. The anxiogenic-like effects of forced swimming stress (10 min) were shown by decreases in the head-dipping behavior, rearing, and locomotor activity in a hole-board task. Interestingly, the administration of the different doses of nicotine (0.075 and 0.1 mg/kg, i.p.) inhibited stress-induced anxiogenic-like behaviors. Bilateral microinjection of NMDA (0.1 µg/rat) into the VH potentiated the response of an ineffective dose of nicotine (0.05 mg/kg, i.p.) on stress-induced anxiety-like behavior. The microinjection of D-AP5 (1.5 and 2 µg/rat) into the VH inhibited the response of an effective dose of nicotine (0.1 mg/kg, i.p.) on anxiety-like behavior induced by acute stress. Intra-VH microinjection of D-AP5 reversed the potentiating effect of NMDA on nicotine response. Intra-VH microinjection of NMDA or D-AP5 by itself did not affect stress-induced anxiety-like behavior. Taken together, we can conclude that nicotine inhibited stress-induced anxiogenic-like behaviors, possibly via the ventral hippocampal NMDA receptors mechanism.

Effects of forced swimming stress on expression and phosphorylation of PI3K/Akt signal pathway in pancreas of type 2 diabetic rats.

BackgroundTo study the effects of forced swimming stress on blood glucose and insulin levels and the expression and phosphorylation of pancreatic PI3K/Akt signal pathway in type 2 diabetic rats.MethodsThirty adult SD rats (8-week-old, male) were randomly divided into three groups: control group, diabetic model group, and diabetic model stress group. The diabetic model group was established by feeding with the high-fat and high-glucose diet for four weeks, and then the rats were injected with low-dose streptozotocin (STZ, 25 mg/kg, once a day for 2 days). The rats in the diabetic model group were subjected to forced swimming stress for seven days, which was a diabetic model stress group. Twenty-four hours after the last forced swimming stress, the rats fasted, and blood samples were collected to detect blood glucose, insulin, triglycerides (TGs), free fatty acids (FFAs), high- and low-density lipoprotein cholesterol (HDLC and LDLC) levels. The western blot was applied to detect the expression of PI3K, Akt, p-Akt, and mTOR in the pancreas of rats in each group.ResultsBlood glucose and insulin levels in the diabetic model stress group were significantly lower than those in the diabetic model group, and the protein levels of PI3K, p-AKT, and mTOR in the pancreas of the diabetic model stress group were significantly higher than those of the diabetic model group.ConclusionsOne-week swimming stress can decrease the blood glucose level and improve insulin indexes in type 2 diabetic rats and increase the expression and phosphorylation of pancreatic PI3K/Akt signal pathway proteins.

Quantitative analysis of Gria1, Gria2, Dlg1 and Dlg4 expression levels in hippocampus following forced swim stress in mice

AMPA receptors and interacting proteins are importantly involved in mediating stress-dependent plasticity. Previously we reported that GluA1-containing AMPA receptors and their interaction with PDZ-proteins are required for the experience-dependent expression of behavioral despair in the forced swim test. However, it is unclear if the expression of GluA1-containing AMPA receptors is affected by this type of behavior. Here we investigated in wild type mice, whether hippocampal gene or protein levels of GluA1 or associated PDZ proteins is altered following forced swim stress. We show that expression of Dlg4 (the gene coding for PSD-95) was strongly reduced after two days of forced swimming. In contrast, levels of Dlg1, Gria1, and Gria2 (coding for SAP97, GluA1, and GluA2 respectively) were not affected after one or two days of forced swimming. The changes in gene expression largely did not translate to the protein level. These findings indicate a limited acute effect of forced swim stress on the expression of the investigated targets and suggest that the acute involvement of GluA1-containing AMPA receptors tor forced swim behavior is a result of non-genomic mechanisms.

Involvement of orexinergic receptors in the nucleus accumbens, in the effect of forced swim stress on the reinstatement of morphine seeking behaviors

Orexinergic system is involved in primary rewards; the neural circuit of the ventral tegmental area (VTA), nucleus accumbens (NAc), prefrontal cortex and amygdala represents overlapping elements mediating the rewarding effects of drugs and stressful experiences. The NAc integrates reward-related information from the VTA. Also, it has been indicated that orexinergic system activates the mesolimbic dopamine projecting neurons to the NAc and promotes the development of reward in rodents. Therefore, in the present study, the conditioned place preference (CPP) paradigm was used to determine the role of the two types of orexin receptors (OXR) in the NAc in forced swim stress (FSS), as physical stress, and/or priming-induced reinstatement of morphine. The CPP was induced by injecting morphine (5 mg/kg, SC for 3 days) and lasted for eight free-morphine days; the reinstatement was induced by administration of effective priming dose of morphine (1 mg/kg; sc). The extinguished rats received intra-NAc injection of SB334867 as OX1R antagonist or TCSOX229 as OX2R antagonist before effective priming dose injection of morphine (1 mg/kg; sc). In others, the extinguished rats were given intra-NAc injection of SB334867 or TCSOX229 and then, they underwent FSS before injection of ineffective priming dose of morphine (0.5 mg/kg; sc). Our results showed that intra-accumbal administration of SB334867 or TCSOX229 could inhibit morphine priming- and FSS-induced reinstatement of extinguished morphine-seeking in the rats. It seems that OXR in the NAc may be involved in reward and could play an important role in the effect of stress on reinstatement of morphine-seeking behaviors in this area.

Effects of forced swimming stress on thyroid function, pituitary thyroid-stimulating hormone and hypothalamus thyrotropin releasing hormone expression in adrenalectomy Wistar rats.

In order to study the impact that is imposed on the hypothalamic-pituitary-thyroid (HPT) axis of adrenalectomy male Wistar rats by stress caused by swimming, the blood level of triiodothyronine (T3), thyroxine (T4) and thyroid-stimulating hormone (TSH), the expression of TSHβ mRNA at the pituitary and thyrotropin releasing hormone (TRH) expression at the paraventricular nucleus (PVN) were measured. A total of 50 male Wistar rats of 6–8 weeks of age and with an average weight of 190–210 grams were randomly divided into the following two groups: The surgical (without adrenal glands) and non-surgical (adrenalectomy) group. These two groups were then divided into the following five groups, according to the time delay of sacrifice following forced swim (10 min, 2 h, 12 h and 24 h) and control (not subjected to swimming) groups. A bilateral adrenalectomy animal model was established. Serum TSH in the blood was measurement by chemiluminescent immunoassay, and cerebrum tissue were excised for the measurement of TRH expression using an immunohistochemistry assay. In addition, pituitaries were excised for the extraction of total RNA. Finally, reverse transcription-quantitative polymerase chain reaction was performed for quantitation of TSHβ. Following swimming, the serum T3, T4 and TSH, the TSHβ mRNA expression levels in the pituitary and the TRH expression in the PVN of the surgical group were gradually increased. In the non-surgical group, no significant differences were observed in the serum T3, T4 and TSH levels compared with the control group. The TSHβ mRNA expression at the pituitary showed a similar result. Furthermore, the TRH expression at PVN was gradually increased and stress from swimming could increase the blood T4, T3 and TSH levels, TSHβ mRNA expression at the pituitary and TRH expression at the PVN in adrenalectomy Wistar rats. Moreover, the index in the surgical group changed significantly compared with the non-surgical group. In conclusion, the results suggest that there is a positive correlation between stress from forced swimming and the variation of the HPT axis.

The effect of forced swim stress on morphine sensitization: Involvement of D1/D2-like dopamine receptors within the nucleus accumbens

Nucleus accumbens (NAc) plays an essential role in morphine sensitization and suppression of pain. Repeated exposure to stress and morphine increases dopamine release in the NAc and may lead to morphine sensitization. This study was carried out in order to investigate the effect of forced swim stress (FSS), as a predominantly physical stressor and morphine on the development of morphine sensitization; focusing on the function of D1/D2-like dopamine receptors in the NAc in morphine sensitization. Eighty-five adult male Wistar rats were bilaterally implanted with cannulae in the NAc and various doses of SCH-23390 (0.125, 0.25, 1 and 4μg/0.5μl/NAc) as a D1 receptor antagonist and sulpiride (0.25, 1 and 4μg/0.5μl/NAc) as a D2 receptor antagonist were microinjected into the NAc, during a sensitization period of 3days, 5min before the induction of FSS. After 10min, animals received subcutaneous morphine injection (1mg/kg). The procedure was followed by 5days free of antagonist, morphine and stress; thereafter on the 9th day, the nociceptive response was evaluated by tail-flick test. The results revealed that the microinjection of sulpiride (at 1 and 4μg/0.5μl/NAc) or SCH-23390 (at 0.25, 1 and 4μg/0.5μl/NAc) prior to FSS and morphine disrupts the antinociceptive effects of morphine and morphine sensitization. Our findings suggest that FSS can potentiate the effect of morphine and causes morphine sensitization which induces antinociception.

Inhibitory effects of forced swim stress and corticosterone on the acquisition but not expression of morphine-induced conditioned place preference: Involvement of glucocorticoid receptor in the basolateral amygdala

Addiction is a common chronic psychiatric disease which represents a global problem and stress has an important role to increase drug addiction and relapse. In the present study, we investigated the effects of physical stress and exogenous corticosterone on the acquisition and expression of morphine-induced conditioned place preference (CPP). Also, we tried to find out the role of glucocorticoid receptors (GRs) of basolateral amygdala (BLA) in this regard. In the CPP paradigm, conditioning score and locomotion activity were recorded by Ethovision software. Male adult rats received forced swim stress (FSS) as a physical stress or corticosterone (10mg/kg; ip) as a dominant stress hormone in rodents, 10min before morphine injection (5mg/kg; sc) during three conditioning days (acquisition) or just prior to CPP test in the post-conditioning day (expression). In FSS procedure, animals were forced to swim for 6min in cylinder filled with water (24–27°C). To evaluate the role of glucocorticoid receptors in the BLA, different doses of mifepristone (RU38486) as a GR antagonist were injected into the BLA (0.3, 3 and 30ng/side) during 3-day conditioning phase before FSS or injection of corticosterone in morphine-CPP paradigm. The results showed that FSS and corticosterone reduce the acquisition but not expression of morphine-induced CPP. Moreover, blockade of GRs in the BLA could diminish the inhibitory effects of FSS or corticosterone on the acquisition of morphine-induced CPP. It seems that stress exerts its effect on reward pathway via glucocorticoid receptors in the BLA.

Region- and sex-specific changes in CART mRNA in rat hypothalamic nuclei induced by forced swim stress

Cocaine and amphetamine regulated transcript (CART) mRNA and peptides are highly expressed in the paraventricular (PVN), dorsomedial (DMH) and arcuate (ARC) nuclei of the hypothalamus. It has been suggested that these nuclei regulate the hypothalamic–pituitary–adrenal (HPA) axis, autonomic nervous system activity, and feeding behavior. Our previous studies showed that forced swim stress augmented CART peptide expression significantly in whole hypothalamus of male rats. In another study, forced swim stress increased the number of CART-immunoreactive cells in female PVN, whereas no effect was observed in male PVN or in the ARC nucleus of either sex. In the present study, we evaluated the effect of forced swim stress on CART mRNA expression in PVN, DMH and ARC nuclei in both male and female rats. Twelve male (stressed and controls, n=6 each) and 12 female (stressed and controls, n=6 each) Sprague-Dawley rats were used. Control animals were only handled, whereas forced swim stress procedure was applied to the stressed groups. Brains were dissected and brain sections containing PVN, DMH and ARC nuclei were prepared. CART mRNA levels were determined by in situ hybridization. In male rats, forced swim stress upregulated CART mRNA expression in DMH and downregulated it in the ARC. In female rats, forced swim stress increased CART mRNA expression in PVN and DMH, whereas a decrease was observed in the ARC nucleus. Our results show that forced swim stress elicits region- and sex-specific changes in CART mRNA expression in rat hypothalamus that may help in explaining some of the effects of stress.

Forced swim stress elicits region-specific changes in CART expression in the stress axis and stress regulatory brain areas

CART mRNA and peptides are highly expressed in the anatomical structures composing the hypothalamo-pituitary-adrenal (HPA) axis and sympatho-adrenal system. Anatomical and functional studies suggest that CART peptides may have a role in the regulation of the neuroendocrine and autonomic responses during stress. Our previous study showed that CART peptides increased significantly in the male hypothalamus and amygdala 10 min after the forced swim stress. The present study aimed to examine the effect of forced swim stress on CART peptide expression in selected brain regions, including those where CART peptide expression has not been reported before (frontal cortex, pons, medulla oblongata), as well as in endocrine glands related to stress in male Sprague Dawley rats. A total of 16 (n = 8) animals were used, including control groups. Rats were subjected to forced swim on two consecutive days, and sacrificed on the second day, 2 h after the termination of the stress procedure. Frontal cortex, pons, medulla oblongata, hypothalamus, pituitary and adrenal glands were dissected and homogenized. CART peptide expression in these tissues was measured by Western Blotting and six different CART peptide fragments were identified. Our results showed that forced swim stress elicited region-specific changes in CART peptide expression. CART was upregulated in the frontal cortex, hypothalamus, medulla oblongata and adrenal gland while there was no change in the pons and pituitary. Enhanced CART peptide fragments in these brain regions and adrenal glands may have a role in the regulation of the HPA and sympatho-adrenal axis activity during stress response.

Hippocampal neuronal nitric oxide synthase (nNOS) is regulated by nicotine and stress in female but not in male rats

NO (nitric oxide) produced in limbic brain regions has important roles in the regulation of autonomic nervous system and HPA axis activity, anxiety, fear learning, long-term memory formation, and depression. NO is synthesized from l-arginine in a reaction catalyzed by nitric oxide synthase (NOS). Neuronal nitric oxide synthase (nNOS), one of the three isoforms of NOS, is synthesized constitutively in nerve cells. Increasing evidence indicates that nNOS expression in the nervous system may be regulated by stress and nicotinic receptors. Furthermore, data obtained from several studies suggest that signaling pathways induced by stress and nicotinic receptors may converge on various signal transduction molecules to regulate nNOS expression in brain. In the present study, we used Western Blot analysis to test the effect of forced swim stress, chronic nicotine administration, and the combined effect of both procedures on nNOS expression in the hippocampus, amygdala and frontal cortex of the male and female rat brain. Basal nNOS levels of the three brain regions examined did not show sex differences. However, forced swim stress and chronic nicotine administration increased nNOS expression in the hippocampus of female rats. When stress and nicotine were applied together, no additional increment was observed. Stress and nicotine did not regulate nNOS expression in the amygdala and the frontal cortex of either sex. Data obtained from the present study indicate that the regulation of stress and nicotine induced-nNOS expression in rat hippocampus shows sexual dimorphism and nNOS expression in the female rat hippocampus increases by nicotine and stress.

Acute stress affects the physiology and behavior of allergic mice

Physical and psychological stressors have been implicated in acute asthma exacerbation. The objective of the current study was to determine the effects of forced swimming stress (FST) on allergic pulmonary inflammation in BALB/c mice. Eighty female mice were allocated to one of four treatments arranged in a 2 × 2 factorial consisting of two levels of allergy and two levels of stress. The effects of stress and allergy were assessed by examination of cytokines and leukocyte differentials in the bronchoalveolar lavage fluid, corticosterone and immunoglobulin (Ig) E in the plasma, leukocyte differentials in the peripheral blood, natural killer cytotoxicity, and histopathology of the lungs. Behavior was recorded during the FST. Stress and allergy increased plasma corticosterone in mice. Allergy increased IgE concentrations and pulmonary inflammation. Interleukin-4 was greater among allergic stressed and non-stressed mice and stressed, non-allergic mice compared with non-stressed, non-allergic mice. Interleukin-5 (IL-5) and 6 (IL-6) were greater among allergic stressed and non-stressed mice compared with non-allergic mice. Interleukin-5 and 6 were reduced among stressed-allergic mice compared with non-stressed, allergic mice. Stress and allergy shifted mice towards a T-helper 2 response as shown by increased interleukin-4. Stress reduced IL-5 and IL-6 in allergic mice but not non-allergic mice. Pulmonary inflammation was not reduced among allergic stressed mice in spite of elevated glucocorticoids. Mice induced to be allergic responded to FST differently than non-allergic mice. Our findings suggest that stress induces a differential response among allergic and non-allergic mice.

The effects of stressful stimuli and hypothalamic–pituitary–adrenal axis activation are reversed by the melanin-concentrating hormone 1 receptor antagonist SNAP 94847 in rodents

Melanin-concentrating hormone (MCH) is an orexigenic and dipsogenic neuropeptide that has been reported to mediate acute behavioral and neuroendocrine stress-related responses via MCH 1 receptor activation in rodents. The purpose of the present investigation was to use the MCH 1 receptor antagonist SNAP 94847 ( N-(3-{1-[4-(3,4-difluoro-phenoxy)-benzyl]-piperidin-4-yl}-4-methyl-phenyl)-isobutyramide) to determine the effects of MCH 1 receptor blockade on MCH-evoked adrenocorticotropic hormone (ACTH) release, chronic mild stress-induced anhedonia, stress-induced hyperthermia and forced swim stress-induced immobility. The appropriate dose range for testing SNAP 94847 was determined by measuring MCH-evoked water drinking. The corresponding occupancy of MCH 1 receptors in rat striatum was also measured across a broad dose range. Orally administered (p.o.) SNAP 94847 (1–10 mg/kg) corresponds to 30–60% occupancy at MCH 1 receptors and significantly blocks water drinking induced by the intracerebroventricular (i.c.v.) injection of MCH. MCH (i.c.v.) significantly elevates plasma levels of ACTH in rats, and SNAP 94847 (2.5 mg/kg, p.o.) blocks MCH-evoked ACTH release. Using the chronic mild stress paradigm, we show that repeated daily exposure to environmental stressors for 5 weeks significantly suppresses sucrose intake in rats, and that SNAP 94847 (1 mg/kg, BID) for 1–5 weeks restores baseline sucrose intake. Moreover, a single administration of SNAP 94847 attenuates stress-induced hyperthermia and the behavioral effects of forced swim stress with minimal effective doses of 2.5 and 30 mg/kg (p.o.), respectively. The regulation of ACTH release and reversal of the effects of chronic and acute stress by SNAP 94847 are suggestive of a role for MCH 1 receptor blockade in the treatment of disorders characterized by high allostatic load.

Upregulation of Voluntary Alcohol Intake, Behavioral Sensitivity to Stress, and Amygdala Crhr1 Expression Following a History of Dependence

A history of alcohol dependence recruits increased voluntary alcohol intake and sensitivity to stress. Corticotropin-releasing hormone (CRH) has been implicated in this transition, but underlying molecular mechanisms remain unclear. A postdependent state was induced using intermittent alcohol exposure. Experiments were carried out following > or =3 weeks of recovery to eliminate contributions of acute withdrawal. Voluntary alcohol consumption was assessed in a two-bottle, free choice procedure. Behavioral sensitivity to stress was examined using fear suppression of behavior in a punished drinking (Vogel) conflict test. Effects of forced swim stress on voluntary alcohol intake were examined as a function of exposure history. Expression of Crh, Crhr1, and Crhr2 transcripts was analyzed by in situ hybridization histochemistry. Alcohol drinking was upregulated long-term following a history of dependence. Fear suppression of behavior was selectively potentiated in postdependent animals. This persisted 3 months after alcohol exposure and was reversed by the selective CRH-R1 antagonist 3-(4-Chloro-2-morpholin-4-yl-thiazol-5-yl)-8-(1-ethylpropyl)-2,6-dimethyl-imidazo[1,2-b]pyridazine (MTIP) (10 mg/kg). Forced swim stress increased alcohol intake in postdependent animals but not in control animals. Behavioral changes were paralleled by an upregulation of Crhr1 transcript expression within basolateral (BLA) and medial (MeA) amygdala and Crh messenger RNA (mRNA) in central amygdala (CeA). In contrast, Crhr2 expression was down in the BLA. Neuroadaptations encompassing amygdala CRH signaling contribute to the behavioral phenotype of postdependent animals.

Effects of forced swimming stress on rat brain function

Chronic stress has been reported to be an essential factor for depression. In this study, the effect of forced swimming stress on neurotransmitters and cellular signaling pathway contributing to brain functions was investigated using the forced swimming test (FST) in order to understanding of mechanisms to regulate stress signals in brain. Antidepressant drug, imipramine, significantly reduced the immobility time of male rats in the FST by 85% at a dose of 15 mg/kg for 2 weeks. This result indicated that the swimming stress caused a depressed state in the rats without administration of imipramine. Swimming stress significantly lowered the serotonergic ratio and also markedly enhanced the phosphorylation of ERK1/2 in the hypothalamus region compared to the rats without FST. These phenomena may be included in key mechanisms of the development of depression.

κ Opioid Receptor Antagonism and Prodynorphin Gene Disruption Block Stress-Induced Behavioral Responses

Previous studies have demonstrated that stress may increase prodynorphin gene expression, and kappa opioid agonists suppress drug reward. Therefore, we tested the hypothesis that stress-induced release of endogenous dynorphin may mediate behavioral responses to stress and oppose the rewarding effects of cocaine. C57Bl/6 mice subjected to repeated forced swim testing (FST) using a modified Porsolt procedure at 30 degrees C showed a characteristic stress-induced immobility response and a stress-induced analgesia observed with a tail withdrawal latency assay. Pretreatment with the kappa opioid receptor antagonist nor-binaltorphimine (nor-BNI; 10 mg/kg, i.p.) blocked the stress-induced analgesia and significantly reduced the stress-induced immobility. The nor-BNI sensitivity of the behavioral responses suggests an activation of the kappa opioid receptor by a stress-induced release of dynorphin peptides. Supporting this hypothesis, transgenic mice possessing a disrupted prodynorphin gene showed no increase in immobility or stress-induced analgesia after exposure to repeated FST. Because both stress and the kappa opioid system can modulate the response to drugs of abuse, we tested the effects of forced swim stress on cocaine-conditioned place preference (CPP). FST-exposed mice conditioned with cocaine (15 mg/kg, s.c.) showed significant potentiation of place preference for the drug-paired chamber over the responses of unstressed mice. Surprisingly, nor-BNI pretreatment blocked stress-induced potentiation of cocaine CPP. Consistent with this result, mice lacking the prodynorphin gene did not show a stress-induced potentiation of cocaine CPP, whereas wild-type littermates did. The findings suggest that chronic swim stress may activate the kappa opioid system to produce analgesia, immobility, and potentiation of the acute rewarding properties of cocaine in C57Bl/6 mice.