Acute Stress Model Research Articles

A review on animal models for screening potential anti-stress agents

Stress is a state of threatened homeostasis that produces different physiological as well as pathological changes depending on severity, type and duration of stress. The animal models are pivotal for understanding the pathophysiology of stress-induced behavioral alterations and development of effective therapy for its optimal management. A battery of models has been developed to simulate the clinical pain conditions with diverse etiology. An ideal animal model should be able to reproduce each of the aspects of stress response and should be able to mimic the natural progression of the disease. The present review describes the different types of acute and chronic stress models including immersion in cold water with no escape, cold environment isolation, immobilization/restraint-induced stress, cold-water restraint stress, electric foot shock-induced stress, forced swimming-induced stress, food-deprived activity stress, neonatal isolation-induced stress, predatory stress, day-night light change-induced stress, noise-induced stress, model of post-traumatic stress disorder and chronic unpredictable stress models.

The role of CRH in behavioral responses to acute restraint stress in zebrafish

In teleosts, changes in swimming, exploring, general locomotor activity, and anxious state can be a response to stress mediated by the corticotropin-releasing hormone system activation and its effects on glucocorticoid levels. Zebrafish has been widely used to study neuropharmacology and has become a promising animal model to investigate neurobehavioral mechanisms of stress. In this report the animals were submitted to acute restraint stress for different time lengths (15, 60 and 90 min) for further evaluation of behavioral patterns, whole-body cortisol content, and corticotropin-releasing hormone expression. The results demonstrated an increase in the locomotor activity and an alteration in the swimming pattern during a 5-min trial after the acute restraint stress. Interestingly, all groups of fish tested in the novel tank test exhibited signs of anxiety as evaluated by the time spent in the bottom of the tank. Whole-body cortisol content showed a positive correlation with increased behavioral indices of locomotion in zebrafish whereas molecular analysis of corticotropin-releasing hormone showed a late reduction of mRNA expression (90 min). Altogether, we present a model of acute restraint stress in zebrafish, confirmed by elevated cortisol content, as a valid and reliable model to study the biochemical basis of stress behavior, which seems to be accompanied by a negative feedback of corticotropin-release hormone mRNA expression.

Mass spectrometry-based quantification of myocardial protein adducts with acrolein in an in vivo model of oxidative stress.

Acrolein (ACR) exposure leads to the formation of protein-ACR adducts. Protein modification by ACR has been associated with various chronic diseases including cardiovascular and neurodegenerative diseases. Here, we report an analytical strategy that enables the quantification of Michael-type protein adducts of ACR in mitochondrial proteome samples using liquid chromatography in combination with tandem mass spectrometry and selected ion monitoring (LC-MS/MS SRM) analysis. Our approach combines site-specific identification and relative quantification at the peptide level of protein-ACR adducts in relation to the unmodified protein thiol pool. Treatment of 3-month-old rats with CCl(4) , an established in vivo model of acute oxidative stress, resulted in significant increases in the ratios of distinct ACR-adducted peptides to the corresponding unmodified thiol-peptides obtained from proteins that were isolated from cardiac mitochondria. The mitochondrial proteins that were found adducted by ACR were malate dehydrogenase, NADH dehydrogenase [ubiquinone] flavoprotein 1, cytochrome c oxidase subunit VIb isoform 1, ATP synthase d chain, and ADP/ATP translocase 1. The findings indicate that protein modification by ACR has potential value as an index of mitochondrial oxidative stress.

Modulating Effect of Interleukin-4 on Free Radical Processes in the Brain of Rats during Emotional Stress

We studied the effect of anti-inflammatory cytokine IL-4 on the intensity of free radical processes in emotiogenic brain structures (hypothalamus, sensorimotor cortex, and amygdala) in rats with different prognostic emotional resistance. One-hour immobilization of animals with simultaneous electrocutaneous stimulation was used as a model of acute stress. The stress was accompanied by accumulation of MDA (LPO end-product) in the sensorimotor cortex and amygdala of passive rats. Intraperitoneal administration of IL-4 (5 μg/kg) increased MDA content in the amygdala and hypothalamus of non-stressed rats with different behavioral activity. In the sensorimotor cortex of passive and, especially, active rats, a decrease in MDA level was observed after injection of this cytokine. Preliminary administration of IL-4 prevented LPO activation in the sensorimotor cortex of behaviorally passive animals observed after stress against the background of saline injection. Regional peculiarities of LPO under the influence of this cytokine can be determined by differences in both biochemical processes in the brain tissue and specific involvement of different emotiogenic structures in the formation of the stress response. The revealed differences in the effects of IL-4 on free radical processes in active and passive rats indicate peculiarities of immune mechanisms in animals with different resistance to the same type of stress.

Diazepam Blocks Striatal Lipid Peroxidation and Improves Stereotyped Activity in a Rat Model of Acute Stress

In this work, the effect of a single dose of diazepam was tested on different markers of oxidative damage in the striatum of rats in an acute model of immobilization (restraint) stress. In addition, the locomotor activity was measured at the end of the restraint period. Immobilization was induced to animals for 24 hr, and then, lipid peroxidation, superoxide dismutase activity and content, and mitochondrial function were all estimated in striatal tissue samples. Corticosterone levels were measured in serum. Diazepam was given to rats as a pre-treatment (1 mg/kg, i.p.) 20 min. before the initiation of stress. Our results indicate that acute stress produced enhanced striatal levels of lipid peroxidation (73% above the control), decreased superoxide dismutase activity (54% below the control), reduced levels of mitochondrial function (35% below the control) and increased corticosterone serum levels (86% above the control). Pre-treatment of stressed rats with diazepam decreased the striatal lipid peroxidation levels (68% below the stress group) and improved mitochondrial function (18% above the stress group), but only mild preservation of superoxide dismutase activity was detected (17% above the stress group). In regard to the motor assessment, only the stereotyped activity was increased in the stress group with respect to control (46% above the control), and this effect was prevented by diazepam administration (30% below the stress group). The preventive actions of diazepam in this acute model of stress suggest that drugs exhibiting anxiolytic and antioxidant properties might be useful for the design of therapies against early acute phases of physic stress.

Upregulation of peroxiredeoxin III in the hippocampus of acute immobilization stress model rats and the Foxo3a-dependent expression in PC12 cells.

Stress induces structural plasticity in neurons of the adult central nervous system (CNS) and alters the levels of cellular production of reactive oxygen species (ROS), and these changes might involve modifications of the antioxidant defense system. This study investigated whether acute stress altered the expression pattern of peroxiredoxin (Prx) III, which is an antioxidant enzyme that controls cytokine-induced peroxide levels. Prx III immunoreactivity was upregulated in the pyramidal neurons of the hippocampus and in the motor neurons of the spinal cord in an acute immobilization stress (AIS) model. In addition, we tested whether the transcription factor Foxo3a was necessary for the expression of Prx III. The depletion of Foxo3a led to a marked reduction of Prx III and a compensatory enhancement of mitochondrial superoxide dismutase (Mn-SOD) in PC12 cells. The results of this study suggest that Foxo3a mediates the neuronal levels of expression of Prx III and the levels of expression of Mn-SOD in mitochondria. These mechanisms may play an important role in neuroprotection against oxidative stress. Furthermore, Prx III upregulation might be an useful approach for the management of stress.

Potent and Selective Inhibitors of the Inositol-requiring Enzyme 1 Endoribonuclease

Inositol-requiring enzyme 1 (IRE1) is the most highly conserved signaling node of the unfolded protein response (UPR) and represents a potential therapeutic target for a number of diseases associated with endoplasmic reticulum stress. IRE1 activates the XBP-1 transcription factor by site-specific cleavage of two hairpin loops within its mRNA to facilitate its nonconventional splicing and alternative translation. We screened for inhibitors using a construct containing the unique cytosolic kinase and endoribonuclease domains of human IRE1α (hIRE1α-cyto) and a mini-XBP-1 stem-loop RNA as the substrate. One class compounds was salicylaldehyde analogs from the hydrolyzed product of salicylaldimines in the library. Salicylaldehyde analogs were active in inhibiting the site-specific cleavage of several mini-XBP-1 stem-loop RNAs in a dose-dependent manner. Salicyaldehyde analogs were also active in inhibiting yeast Ire1 but had little activity inhibiting RNase L or the unrelated RNases A and T1. Kinetic analysis revealed that one potent salicylaldehyde analog, 3-ethoxy-5,6-dibromosalicylaldehyde, is a non-competitive inhibitor with respect to the XBP-1 RNA substrate. Surface plasmon resonance studies confirmed this compound bound to IRE1 in a specific, reversible and dose-dependent manner. Salicylaldehydes inhibited XBP-1 splicing induced pharmacologically in human cells. These compounds also blocked transcriptional up-regulation of known XBP-1 targets as well as mRNAs targeted for degradation by IRE1. Finally, the salicylaldehyde analog 3-methoxy-6-bromosalicylaldehyde strongly inhibited XBP-1 splicing in an in vivo model of acute endoplasmic reticulum stress. To our knowledge, salicylaldehyde analogs are the first reported specific IRE1 endoribonuclease inhibitors.

Early Changes in Oxidative Stress Markers in a Rat Model of Acute Stress: Effect of l-carnitine on the Striatum

This work focuses on the effect of acute stress on different markers of oxidative stress and mitochondrial dysfunction in the rat striatum. In addition, the effect of a single dose of l-carnitine (l-CAR, 300 mg/kg, i.p.) was evaluated in these animals. Immobilization (restraint) stress was induced to rats for 24 hr. The levels of lipid peroxidation (LP) and mitochondrial function (MF), as well as the superoxide dismutase (SOD) activity and content and reduced glutathione (GSH) levels, were all measured in striatal samples of animals subjected to stress. Our results indicate that acute stress is able to increase the striatal LP and reduced the levels of MF, while significantly lowered the manganese superoxide dismutase (Mn-SOD) activity. No changes were observed in the total striatal content of SOD, nor in GSH levels, but serum corticosterone content was increased by stress. l-CAR exhibited partial protective effects on the immobilized group, reducing the striatal LP and recovering the striatal MF and Mn-SOD activity. Our results suggest that acute restraint stress brings an accurate model for early pro-oxidant responses that can be targeted by broad-spectrum antioxidants like l-CAR.

L-Serine Decreases Taurine Concentration in the Extracellular Fluid of Brain Slices

L-Serine is considered a functional amino acid in the central nervous system, and induces sedation and hypnotic effects in some animal models of acute and chronic stress. Accordingly, while L-serine is a candidate anti-stress factor, the central mechanism of L-serine is not clear. The present study clarifies the action of L-serine using acute chick brain slices. We investigated the changes in some extracellular fluid amino acid concentrations in response to L-serine perfusion. Taurine concentration decreased while L-alanine concentration increased following L-serine perfusion. To examine the involvement of the taurine transporter, the effect of L-serine on the taurine concentration in the presence and absence of Na+ was also investigated. Na+ had no effect on taurine concentration induced by L-serine perfusion. These results suggest that L-serine has an ability to promote L-alanine synthesis facilitating the catabolism of taurine. In conclusion, L-serine modifies the metabolism of taurine and L-alanine in the extracellular space in chick brain.

Acute Stress Elicited by Bungee Jumping Suppresses Human Innate Immunity

Although a relation between diminished human immunity and stress is well recognized both within the general public and the scientific literature, the molecular mechanisms by which stress alters immunity remain poorly understood. We explored a novel model for acute human stress involving volunteers performing a first-time bungee jump from an altitude of 60 m and exploited this model to characterize the effects of acute stress in the peripheral blood compartment. Twenty volunteers were included in the study; half of this group was pretreated for 3 d with the β-receptor blocking agent propranolol. Blood was drawn 2 h before, right before, immediately after and 2 h after the jump. Plasma catecholamine and cortisol levels increased significantly during jumping, which was accompanied by significantly reduced ex vivo inducibility of proinflammatory cytokines as well as activation of coagulation and vascular endothelium. Kinome profiles obtained from the peripheral blood leukocyte fraction contained a strong noncanonical glucocorticoid receptor signal transduction signature after jumping. In apparent agreement, jumping down-regulated Lck/Fyn and cellular innate immune effector function (phagocytosis). Pretreatment of volunteers with propranolol abolished the effects of jumping on coagulation and endothelial activation but left the inhibitory effects on innate immune function intact. Taken together, these results indicate that bungee jumping leads to a catecholamine-independent immune suppressive phenotype and implicate noncanonical glucocorticoid receptor signal transduction as a major pathway linking human stress to impaired functioning of the human innate immune system.

Effect of Interleukin-1β on Lipid Peroxidation in Emotiogenic Structures of the Brain in Rats during Acute Stress

We studied the effects of immunomodulatory cytokine interleukin-1β on lipid peroxidation in emotiogenic structures of the brain (hypothalamus, sensorimotor cortex, and amygdala) of behaviorally active and passive rats with different prognostic resistance to stress. Immobilization of animals with simultaneous electrocutaneous stimulation (1 h) served as the model of acute emotional stress. Intraperitoneal injection of IL-1β (5 μg/kg) was followed by accumulation of malonic dialdehyde (end-product of lipid peroxidation) in all structures of the brain in passive rats, as well as in the hypothalamus of active animals. As differentiated from active rats, stress exposure in passive specimens was accompanied by a selective increase in malonic dialdehyde content in the sensorimotor cortex and amygdala. Pretreatment with IL-1β prevented activation of lipid peroxidation in the studied structures of the brain in passive rats after stress exposure. Our results show the specific effect of IL-1β on free-radical processes in the hypothalamus, sensorimotor cortex, and amygdala in rats with various behavioral parameters. Regional features of lipid peroxidation in emotiogenic structures of the brain in animals with different emotional reactivity probably contribute to the existence of significant variations in the individual resistance to emotional stress.

Plasminogen Deficiency Impairs Erythropoietic Recovery Capacity In Male C57BL/6J Mice through Testosterone Defect

AbstractAbstract 3212Plasminogen (Plg), a classical fibrinolytic factor, is essential for maintaining homeostasis of blood coagulation, and has important roles in wound healing as well as pathophysiology of atherosclerosis, cancer and Alzheimer's disease. Recently, we have shown that the activation of the Plg fibrinolytic pathway is critical for hematopoietic regeneration from stem cells after myelosuppression. Here, we investigated the role of Plg in regulating erythropoiesis.Male and female C57BL/6J mice with normal or homozygously disrupted Plg genes were used under steady state conditions and in a model of acute erythropoietic stress selectively induced by intravenous injection of the hemolytic drug phenylhydrazine hydrochloride. Orbital vein blood, bone marrow and spleen were obtained to determine erythropoietic parameters. In addition, testosterone concentrations were measured in murine serum.Normochromic normocytic anemia was found in Plg-/- mice under steady state conditions. Microscopic evaluation of blood smears revealed the presence of altered erythrocytes, such as acanthocytes, echinocytes (burr cells) and to lesser extent schistocytes. In addition, flow cytometry of intravenously injected autologous erythrocytes, labeled with a fluorescent probe, showed significantly shortened erythrocyte lifespan, suggestive of hemolysis as a cause of the anemia. In concordance, there was an increase in plasma erythropoietin with augmented reticulocyte counts, erythroid burst forming units in bone marrow, and finally erythroid progenitors in spleens, which were significantly enlarged, suggestive of extramedullar erythropoiesis. Interestingly, the intensity of compensatory erythropoiesis was higher in Plg-/- female mice, resulting in lesser hematocrit decrease when compared to that observed in Plg-/- male mice. In addition, similar gender differences could be observed in a model of acute erythropoietic stress. Concretely, acute hemolytic anemia induced by intravenous injection of phenylhydrazine hydrochloride resulted in a significant erythrocyte recovery delay in Plg-/- male mice that, in contrast, was not as profound in Plg-/- female mice. To understand the reason for the observed gender differences, a competitive enzyme immunoassay was employed to measure serum concentrations of testosterone. As a result, a significant decrease in serum testosterone levels was detected in Plg-/- male mice.In summary, we found that Plg plays important role in maintaining normal lifespan of erythrocytes by preventing their mechanical alteration by microangiopathy from abnormal fibrin deposition. In addition, given that testosterone is well known to regulate erythropoiesis, through increasing erythropoietin levels as well as having non-erythropoietin stimulating effects, our present results suggest that Plg might also play roles in regulating erythropoiesis through being important for normal testosterone production. Disclosures:No relevant conflicts of interest to declare.

The role of neurotrophins related to stress in saliva and salivary glands.

Nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) are well-studied neurotrophins involved in neurogenesis, differentiation, growth, and maintenance of selected peripheral and central populations of neuronal cells during development and adulthood. Neurotrophins, in concert with the hypothalamic-pituitary-adrenal (HPA) axis, play key roles in modulating brain plasticity and behavioral coping, especially during ontogenetic critical periods, when the developing brain is particularly sensitive to external stimuli. Early life events, such as psychophysical stress, affect NGF and BDNF levels and induce dysregulation of the HPA axis, thereby affecting brain development and contributing to inter-individual differences in vulnerability to stress or psychiatric disorders. Immobilization stress modifies BDNF mRNA expression in some organs. We studied the effect of immobilization stress on BDNF and its receptor tyrosine receptor kinase B (TrkB) in rat submandibular glands, and found increased BDNF expression in duct cells under immobilization stress. Upon further investigation on the influence of salivary glands on plasma BDNF using an acute immobilization stress model, we found that acute immobilization stress lasting 60 min significantly increases the plasma BDNF level. However, plasma BDNF elevation is markedly suppressed in bilaterally sialoadenectomized rats. This suggests that salivary glands may be the primary source of plasma BDNF under acute immobilization stress. This report reviews the structure of salivary glands, the role of neurotrophins in salivary glands, and the significance of BDNF in saliva and salivary glands, followed by a summary of the evidence that indicates the relationship between immobilization stress and BDNF expression within salivary glands.

Quantitative evaluation of tryptophan oxidation in actin and troponin I from skeletal muscles using a rat model of acute oxidative stress

Increased levels of "ROS" cause oxidative stress and are believed to play a key role in the development of age-related diseases and mammalian aging, e.g. through the oxidation of residues, at or close to, the protein surface. In this study, we have investigated the effects of ROS on tryptophan residues in alpha skeletal actin and troponin I (fast skeletal muscle isoform) using an established rat model of acute oxidative stress induced by X-ray irradiation. In the control samples (no oxidative stress), the single Trp residue of troponin I (position 161) and the four tryptophan residues present in actin (positions 79, 86, 340, and 356) were only oxidized at very low levels. Post-irradiation, the level of oxidized versions increased for most positions within 3 h. Tryptophan residues located inside the proteins, however, required longer time periods. Based on the increment masses of the tryptophan positions calculated from the b- and y-ion series of the tandem mass spectra, the following oxidation products of tryptophan were detected: kynurenine; oxolactone; hydroxytryptophan or oxindolylalanine (isobaric); hydroxykynurenine; dioxindolylalanine, N-formylkynurenine or dihydroxytryptophan (all three isobaric); and hydroxyl-N-formylkynurenine, with mass gains relative to tryptophan of 4, 14, 16, 20, 32, and 48 u, respectively. Despite a partial recovery after 24 h, the degree of oxidation of all oxidized versions was still higher than in the control samples.

Poly ADP-ribose polymerase-1 and health

Niacin (vitamin B(3)) is required to form nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP), which are involved in scores of anabolic and catabolic redox reactions throughout metabolism. It is now understood that NAD(+) is also a substrate for several families of ADP-ribosylation reactions, which control processes like DNA repair, replication and transcription, the activity of G-proteins, chromatin structure and intracellular calcium signalling. Poly(ADP-ribose)polymerase-1 (PARP-1) is the most active of the PARP enzymes, and it has been implicated in both prevention and aggravation of disease processes. Inhibition of poly-ADP-ribose formation will tend to cause genomic instability and tumorigenesis in chronic models of DNA damage, but the same inhibition can prevent many acute disease processes, such as stroke, myocardial infarction and septic shock. In models of acute stress, PARP-1 inhibition may protect cellular NAD pools and prevent nuclear factor-kappaB-dependent inflammatory signalling, while long-term protective roles for PARP-1 include DNA repair and regulation of chromatin structure. Promising new PARP-1 inhibitors may display interactions with dietary niacin status and may have long-term deleterious effects on genomic stability, but may be extremely valuable for the treatment of acute inflammatory conditions.

Identification, Quantification, and Functional Aspects of Skeletal Muscle Protein-Carbonylation in Vivo during Acute Oxidative Stress

Reactive oxidative species (ROS) play important roles in cellular signaling but can also modify and often functionally inactivate other biomolecules. Thus, cells have developed effective enzymatic and nonenzymatic strategies to scavenge ROS. However, under oxidative stress, ROS production is able to overwhelm the scavenging systems, increasing the levels of functionally impaired proteins. A major class of irreversible oxidative modifications is carbonylation, which refers to reactive carbonyl-groups. In this investigation, we have studied the production and clearance rates for skeletal muscle proteins in a rat model of acute oxidative stress over a time period of 24 h using a gel-based proteomics approach. Optimized ELISA and Western blots with 10-fold improved sensitivities showed that the carbonylation level was stable at 4 nmol per mg protein 3 h following ROS induction. The carbonylation level then increased 3-fold over 6 h and then remained stable. In total, the oxidative stress changed the steady state levels of 20 proteins and resulted in the carbonylation of 38 skeletal muscle proteins. Carbonylation of these proteins followed diverse kinetics with some proteins being highly carbonylated very quickly, whereas others peaked in the 9 h sample or continued to increase up to 24 h after oxidative stress was induced.

Identification of Cysteine, Methionine and Tryptophan Residues of Actin Oxidized In vivo during Oxidative Stress

Increased levels of reactive oxygen species (ROS) cause oxidative stress and are believed to play a key role in the development of age-related diseases and mammalian aging in general by oxidizing proteins, lipids, and DNA. In this study, we have investigated the effects of ROS on actin in an established rat model of acute oxidative stress using short-term X-ray irradiation. Relative to the control, the actin functions studied in vitro were reduced for (i) actin polymerization to a minimum of 33% after 9 h and (ii) actin activated Mg(2+)-ATPase activity of myosin to 55% after 9 h. At 24 h, the activities had partially recovered to 64 and 80% of the control sample, respectively. The underlying oxidative modifications were also studied at the molecular level. The content of reactive carbonyl-groups increased 4-fold within the studied 24 h period. Among the five cysteine residues of actin, Cys(239) and Cys(259) were oxidized to sulfenic (Cys-SOH), sulfinic (Cys-SO(2)H), or sulfonic (Cys-SO(3)H) acids by increasing amounts over the time periods studied. The content of methionine sulfoxides also increased for 15 of the 16 methionine residues, with Met(44), Met(47), and Met(355) having the highest sulfoxide contents. Met(82) was also further oxidized to the sulfone. Among the four tryptophan residues present in actin, only Trp(79) and Trp(86) appeared to undergo oxidation. The relative contents of hydroxy-tryptophan, N-formyl-kynurenine, and kynurenine increased after irradiation, reaching a maximum in the 9 h sample.

Blocking β2-adrenergic receptor attenuates acute stress-induced amyloid β peptides production

Environmental factors play an important role in the Alzheimer's disease (AD) development and stress may accelerate the progression of AD. β-adrenergic receptors are activated by stress and may influence different aspects of cognitive function. So, it was hypothesized that stress may accelerate the pathological progression of AD by the activation of β 2-adrenergic receptor (β 2-AR). We have investigated the role of acute stress and activation of β 2-AR in amyloid β (Aβ) peptides production in a mouse model of acute restraint stress. Injections of the β 2-AR-selective agonist clenbuterol hydrochloride enhanced the production of acute stress-induced Aβ peptides production; the β 2-AR-selective antagonist ICI 118,551 reduced Aβ peptides production. It is suggested that acute stress induces abnormal activation of β 2-AR which subsequently enhances Aβ peptides (the main neuropathological hallmarks of AD) production possibly resulting in the onset of AD. The findings indicate that new therapeutic strategies designed to blocking β 2-AR might be valuable for the prevention and treatment of AD.

The expression of cholecystokinin and prolactin in cerebral cortex of developing rats with seizure induced by acute heat stress

Objective To analyze the distribution of cholecystokinin (CCK) and prolactin (PRL) positive cells in rat' s brain following heat stress (HS) and febrile convulsion ( FC). Methods Acute heat stress model of seizure induced by warm water was developed in this study. Adjacent section immunohistochemical staining method was used to observe expression of CCK and PRL in cerebral cortex. Results (1) There were similar distributions of CCK and PRL positive cells in cerebral cortex of HS group. (2) Both HS and FC rats showed more positive neurons in cerebral cortex than those in control group (P ＜ 0. 01). There were significant more CCK positive neurons in cerebral cortex than that in HS group(P ＜0. 01) .however,no significant difference of PRL positive neurons was found in piriform cortex and entorhinal cortex between HS and FC group(P＞0.05) ,but the difference was significant in perirhinal cortex and parietal cortex. (3)Correlation and regression analysis of the data of CCK and PRL positive units demonstrated that the immunoreactive intensity of CCK and PRL had a positive linear correlation in cerebral cortex of HS group ( Y = 7. 939 +1. 36X, r = 0. 97, P ＜ 0. 01), but no correlation was found in cerebral cortex of FC group ( r = 0. 47, P ＞0.05). Conclusion (1) CCK may involve in anti-convulsant mechanisms in response to FC. (2) There may be a synergistic action of PRL and CCK in the central control of HS. Key words: Convulsion; Heat stress; Cholecystokinin; Prolactin; Rat

Acute and/or chronic stress models modulate CuZnSOD and MnSOD protein expression in rat liver

Cellular protection against oxidative stress is afforded by the enzyme superoxide dismutase (SOD). In this study, the protein levels of copper-zinc SOD (CuZnSOD) in the cytosolic and nuclear fraction, manganese SOD (MnSOD) in the mitochondrial, and cytosolic fraction and cytochrome c (cyt c) in the liver of male rats exposed to 2 h of acute immobilization (IM) or Cold stress, 21 days chronic isolation or their combinations (chronic/acute stress) were examined. The serum corticosterone (CORT) level was measured, as an indicator of stress stimuli. Both acute stressors with elevated CORT levels caused a decrease of mitochondrial MnSOD, while acute IM resulted in redistribution of the CuZnSOD protein level between the cytosolic and nuclear fraction. Chronic isolation, during which the CORT level was close to control value, resulted in an increase of cytosolic CuZnSOD, whereas a decrease of MnSOD in mitochondrial and its corresponding increase in cytosol fraction was found. In both combined stress regimes, an increase of the CuZnSOD and MnSOD levels in the cytosolic fraction was recorded whereby increase of the CORT level was observed only in the chronic isolation followed by acute IM. The data indicate that acute and/or chronic stress models have different degrees of influence on serum CORT and SOD subcellular protein levels. Increased cytosolic CuZnSOD protein level under chronic isolation suggests that state of oxidative stress may also exist under CORT level similar to the basal value. The presence of MnSOD and cyt c in the cytosolic fraction could serve as useful parameters for mitochondrial dysfunction.