Oxidative stress mediates dibutyl phthalateinduced anxiety-like behavior in Kunming mice

Among all phthalate esters, dibutyl phthalate (DBP) is only second to di-(2-ethylhexyl) phthalate (DEHP) in terms of adverse health outcomes, and its potential cerebral neurotoxicity has raised concern in recent years. DBP exposure has been reported to be responsible for neurobehavioral effects and related neurological diseases. In this study, we found that neurobehavioral changes induced by DBP may be mediated by oxidative damage in the mouse brain, and that the co-administration of Mangiferin (MAG, 50 mg/kg/day) may protect the brain against oxidative damage caused by DBP exposure. The results of ethological analysis (elevated plus maze test and open-field test), histopathological examination of the brain, and assessments of oxidative stress (OS) in the mouse brain showed that there is a link between oxidative stress and anxiety-like behavior produced by DBP at higher doses (25 or 125 mg/kg/day). Biomarkers of oxidative stress encompass reactive oxygen species (ROS), glutathione (GSH), malondialdehyde (MDA) and DPC coefficients (DPC). MAG (50 mg/kg/day),administered as an antioxidant,can attenuatetheanxiety-like behavior of the tested mice.     

Behavioral and neurochemical changes following predatory stress in mice

This article had several objectives. First it aimed at investigating the anxiogenic-like behaviors elicited by unavoidable cat exposure and/or cat odor across nine strains of mice (BALB/c, C57BL/6, C3H, CBA, DBA/2, NMRI, NZB, SJL, Swiss) in a modified version of the free-exploration test. The second objective was to investigate possible neurochemical changes following cat exposure in Swiss mice by measuring the turnover of dopamine (DA), noradrenaline (NA) and serotonin (5-HT) in several brain regions known to be involved in the modulation of emotional processes (hippocampus, hypothalamus and striatum). Finally, the third objective was to examine the effects of anxiolytic drug treatments on the anxiogenic responses elicited by a cat odor (i.e. a feces) in Swiss mice previously exposed to a cat using the free-exploration test. Results from the strain comparison showed that mice could be divided into three distinct groups: two non-reactive strains (NZB and SJL) which were relatively insensitive to predatory exposure and/or odor; five intermediate-reactive strains (Swiss, NMRI, CBA, C3H and BALB/c) which displayed clear anxiogenic-like responses only when exposed to both cat and, subsequently, to feces; and two high reactive strains (C57BL/6 and DBA/2) which showed anxiogenic-like reactions following cat exposure, regardless of the stimulus (clay or feces) present in the free-exploration cage. Neurochemical data revealed that, while brain levels of NA, DA, 5-HT in cat exposed Swiss mice were not significantly different from those of control animals, turnover rates of these monoamines were increased in the hippocampus (NA and 5-HT), hypothalamus and striatum (DA) after cat exposure. Results from pharmacological experiments indicated that repeated administration of the 5-HT reuptake inhibitor fluoxetine (5-20 mg/kg, twice a day, for 5 days) completely abolished avoidance of the cat feces in Swiss mice previously exposed to the predator. Neither acute nor repeated administration of the classical anxiolytic diazepam was able to reduce avoidance behavior of the anxiogenic stimulus in the free-exploration test. Taken together, these findings indicate that the exposure of mice to unavoidable predatory stimuli is associated with behavioral and neurochemical changes consistent with increased anxiety.     

Sound vibration,a non-invasive stress: antagonism by diazepam

Rats, subjected to sound-vibration stress, showed an abrupt increase in plasma corticosterone (CS). This stimulation was reliably produced using a Burgess brand vibro-graver, a standard tool used for engraving. With the tool set at 8 or coarse, the barrel of the tool was placed on the animal's flank and the point held against the side of the metal cage for 15 s. Plasma CS increased to 29.3±4.7 µg/dl at 15 min and 15.7±1.8 µg/dl at 30 min. These levels were significantly higher than animals pretreated with diazepam, 5 mg/kg IV, 2 h prior to stimulation (9.2±2.0 and 7.4±1.5 µg/dl, respectively). Animals which were pretreated with CGS-8216 (a mixed agonist/antagonist at the benzodiazepine receptor), 2 mg/kg IV, 30 min prior to diazepam had the protective effects of diazepam abolished. Sound/vibration produced a significant elevation in plasma CS in animals given CGS-8216 alone; but, this elevation was significantly lower than in vehicle-treated controls. This comparatively lower plasma CS level suggests a partial-agonist, diazepam-like effect by CGS-8216. Experiments were done in conscious unrestrained male Sprague-Dawley rats with chronic IV catheters. Except for 15 s stimulation exposure, all animals remained isolated in sound-attenuated one-way vision boxes for the duration of the serial blood sampling. Control stimulation exposure involved similar handling without turning on the engraving tool. These results demonstrate: 1) the usefulness of this tool to provide a repeatable stress stimulus; 2) the ability of diazepam to abolish the stress response; 3) that CGS-8216 can antagonize the action of diazepam; and 4) a demonstration of the partial agonist effects of CGS-8216.     

L-NAME prevents anxiety-like and depression-like behavior in rats exposed to restraint stress

Stressful life events contribute to the development of many neuropsychiatric disorders including depression and anxiety. Animal studies based on the relationship of stress and depression or anxiety are scarce and controversial. Moreover, neither the neurobiological basis of anxiety and depression nor the mechanisms responsible for neurochemical regulation by stressful stimuli are well understood. This study was designed to investigate the possible contribution of both acute (2 h) and chronic (2 h X 15 d) restraint stress in the generation of anxiety and depression, and also to find out whether nitric oxide (NO) has a modulatory role in these behavioral reactions. Elevated plus-maze and forced swimming test (FST) were chosen for assessment of anxiety and depression, respectively, and N(G)-nitro L-arginine methyl ester (L-NAME, 10 mg/kg), a NO synthase (NOS) inhibitor, and L-arginine (50 mg/kg), a NO precursor, were used to evaluate the role of nitrergic system in restraint exposed rats. The results showed that acute and chronic stress caused depression-like and anxiety-like behaviors in rats and the acute inhibition of NOS by L-NAME prevented these acute and chronic stress-induced anxiogenesis and depression. These data lead to the conclusion that stress and NO seem to be involved in the generation of anxiety and depression.     

Increases in anxiety-like behavior induced by acute stress are reversed by ethanol in adolescent but not adult rats

Repeated exposure to stressors has been found to increase anxiety-like behavior in laboratory rodents, with the social anxiety induced by repeated restraint being extremely sensitive to anxiolytic effects of ethanol in both adolescent and adult rats. No studies, however, have compared social anxiogenic effects of acute stress or the capacity of ethanol to reverse this anxiety in adolescent and adult animals. Therefore, the present study was designed to investigate whether adolescent [postnatal day (P35)] Sprague-Dawley rats differ from their adult counterparts (P70) in the impact of acute restraint stress on social anxiety and in their sensitivity to the social anxiolytic effects of ethanol. Animals were restrained for 90 min, followed by examination of stress- and ethanol-induced (0, 0.25, 0.5, 0.75, and 1 g/kg) alterations in social behavior using a modified social interaction test in a familiar environment. Acute restraint stress increased anxiety, as indexed by reduced levels of social investigation at both ages, and decreased social preference among adolescents. These increases in anxiety were dramatically reversed among adolescents by acute ethanol. No anxiolytic-like effects of ethanol emerged following restraint stress in adults. The social suppression seen in response to higher doses of ethanol was reversed by restraint stress in animals of both ages. To the extent that these data are applicable to humans, the results of the present study provide some experimental evidence that stressful life events may increase the attractiveness of alcohol as an anxiolytic agent for adolescents.     

Adriamycin-related anxiety-like behavior, brain oxidative stress and myelotoxicity in male Wistar rats

Chemotherapeutic regimens have been indicated to negatively impact the quality of life for patients. Adriamycin (ADR) is an effective chemotherapeutic agent widely employed for the treatment of human's malignancies; however, it may cause serious side effects. The present study was aimed at investigating the effects of acute administration of ADR on cognitive alterations, brain oxidative status and immune dysregulation in male Wistar rats. Treated animals received a single intraperitoneal injection of ADR (7 mg/kg). Control ones received physiological saline only. Behavioral effects were tested in the elevated plus-maze and the open field which showed that drug-treated rats displayed anxious behavior and deteriorations in the locomotive and exploratory activities over the 72 h following ADR injection as compared to controls. Assessment of brain antioxidant capacity in ADR-injected animals revealed an increase in glutathione-S-transferase activities and malondialdehyde levels while a decrease in glutathione concentrations when compared with the vehicle-treated group. Our results indicated that ADR administration decreased total leukocyte, lymphocyte and granulocyte counts, while enhanced monocyte levels. Moreover, white blood cells (WBC) relative counts in ADR-treated rats showed a significant increase in monocytes and granulocytes and a decrease in lymphocytes as compared to controls. This study suggests that ADR-related cognitive impairments are associated with brain oxidative stress and myelosuppression.     

Enhancing effects of Ro 15-1788 on straw-climbing behavior as measured with the straw-suspension method: reversal by diazepam

Ro 15-1788 (0.5, 1, 5, or 20 mg/kg), a pure benzodiazepine receptor antagonist, was studied for its effect on the duration of immobility and the number of straw-climbing attempts in a modified forced-swim test with straw-suspension of rats. A single dose of 20 mg/kg of Ro 15-1788 injected IP prolonged only the duration of immobility with no effect on straw-climbing behavior, whereas both doses of 1 and 5 mg/kg of this compound significantly enhanced the number of straw-climbing attempts in an inverted U-shaped manner. Ro 15-1788 at 1 mg/kg significantly reversed the inhibitory effect of 1 mg/kg of diazepam on the number of straw-climbing attempts. It is suggested that the enhancing effect of low doses of Ro 15-1788 on straw-climbing behavior can be regarded as an index of its anxiogenic effect, by acting via central benzodiazepine receptors.     

Pontine tegmentum lesions increase anxiety-like behavior in rats: a comparison with anxiety produced by beta-CCE

Electrolytic lesions of the pedunculopontine tegmental nucleus (PPTg) have been previously reported to increase anxiety-like behavior in rats. The aim of the present study was to compare these behavioral changes with those produced by an anxiogenic compound, the partial inverse agonist at benzodiazepine receptors, beta-CCE. Three groups of rats, sham-lesioned treated with vehicle, sham-lesioned treated with 10 mg/kg of beta-CCE, and PPTg-lesioned rats treated with vehicle, were tested in the elevated plus-maze, the social-interaction test, and for spontaneous locomotion. Histology showed that lesions were concentrated on the caudal half of the PPTg. Measures of both the PPTg-lesioned and beta-CCE-treated rats indicated increased anxiety-like behavior in the elevated plus-maze and in the social-interaction test. Spontaneous locomotion, measured in the open- field arena, did not differ between sham controls and PPTg-lesioned rats, but was decreased in rats treated with beta-CCE. Our results confirmed that electrolytic lesions of the caudal PPTg produce increased anxiety-like behavior. This behavior is quantitatively and qualitatively similar to that produced by 10 mg/kg of beta-CCE.     

Neuroendocrine effects of diazepam in normal subjects following brief painful stress

The neuroendocrine effects of 5 and 10 mg of oral diazepam were assessed in 10 normal subjects under baseline (prestress) and laboratory-controlled stressful conditions. Although the 10-mg diazepam dose had no effect on cortisol at baseline, it significantly reduced the increase in cortisol produced by 15 minutes of exposure to a painful electrical stimulus. There were no significant effects on growth hormone, beta-endorphin or ACTH, either at baseline or after painful stimulation.     

Chronic unpredictable stress induces a cognitive deficit and anxiety-like behavior in rats that is prevented by chronic antidepressant drug treatment.

Chronic stress is a risk factor for the development of many psychopathological conditions in humans, including major depression and anxiety disorders. There is a high degree of comorbidity of depression and anxiety. Moreover, cognitive impairments associated with frontal lobe dysfunction, including deficits in cognitive set-shifting and behavioral flexibility, are increasingly recognized as major components of depression, anxiety disorders, and other stress-related psychiatric illnesses. To begin to understand the neurobiological mechanisms underlying the cognitive and emotional consequences of chronic stress, it is necessary to employ an animal model that exhibits similar effects. In the present study, a rat model of chronic unpredictable stress (CUS) consistently induced a cognitive impairment in extradimensional set shifting capability in an attentional set shifting test, suggesting an alteration in function of the medial prefrontal cortex. CUS also increased anxiety-like behavior on the elevated plus-maze. Further, chronic treatment both with the selective norepinephrine reuptake blocker, desipramine (7.5 mg/kg/day), and the selective serotonin reuptake blocker, escitalopram (10 mg/kg/day), beginning 1 week before CUS treatment and continuing through the behavioral testing period, prevented the CUS-induced deficit in extradimensional set-shifting. Chronic desipramine treatment also prevented the CUS-induced increase in anxiety-like behavioral reactivity on the plus-maze, but escitalopram was less effective on this measure. Thus, CUS induced both cognitive and emotional disturbances that are similar to components of major depression and anxiety disorders. These effects were prevented by chronic treatment with antidepressant drugs, consistent also with clinical evidence that relapse of depressive episodes can be prevented by antidepressant drug treatment.     

Blockade of CRF1 and CCK2 receptors attenuated the elevated anxiety-like behavior induced by immobilization stress

Two highly co-localized neurotransmitters: corticotropin-releasing factor (CRF) and cholecystokinin (CCK), have been implicated in the development of stress-related anxiety disorders. This study was designed to examine the role of CRF1 and CCK2 receptors on the anxiety-like behavior induced by immobilization stress. Our results showed that 30-min immobilization enhanced the anxiety-like behavior in C57BL/6J mice examined in the elevated plus maze (EPM). The combined pretreatment of CR2945 (a CCK2 receptor antagonist) and antalarmin (a CRF1 receptor antagonist) fully blocked this elevated anxiety-like behavior, while the application of CR2945 or antalarmin alone showed only partial effects. The increased expression of CRF1 and CCK2 receptors at protein levels in three anxiety-related brain regions: cortex, hippocampus and hypothalamus, was detected by Western blot. The increased mRNA expression of CCK, CRF, CCK2 and CRF1 receptors was also examined by real-time RT-PCR. Our study demonstrated that the blockade of CRF1 and CCK2 receptors attenuated the elevated anxiety-like behavior induced by immobilization stress, suggestive of the CRF and CCK systems contributing to the development of stress-related anxiety behavior.     

Elevated anxiety-like behavior following ethanol exposure in mutant mice lacking neuropeptide Y (NPY)

BACKGROUND: Neuropeptide Y (NPY) is a neuromodulator with anxiolytic properties. Recent evidence suggests that NPY modulates neurobiological responses to ethanol. Because withdrawal from ethanol is associated with elevated anxiety-like behavior, and because central NPY modulates anxiety, we assessed anxiety-like behavior in mutant mice lacking normal production of NPY (NPY-/-) and in normal wild-type mice (NPY+/+) 6h after removal of a liquid diet containing 4.5% ethanol. METHODS: NPY-/- and NPY+/+ mice on a pure 129/SvEv genetic background were given 6 days of access to a liquid ethanol diet (ED) or control diet (CD). Six hours before elevated plus maze (EPM) testing, ED was replaced with CD in the ethanol-withdrawn group. RESULTS: Ethanol-withdrawn NPY-/- mice showed significantly less open arm time and total proportion of time spent in the open arm of the EPM relative to ethanol-withdrawn NPY+/+ mice and when compared to NPY-/- and NPY+/+ mice that had access to the CD. On the other hand, ethanol-withdrawn NPY+/+ mice did not show altered EPM behavior relative to controls. CONCLUSIONS: Central NPY is protective against anxiety-like behavior stemming from exposure to and/or withdrawal from ethanol. Targets aimed at NPY receptors may be useful compounds for treating anxiety associated with ethanol dependence.     

Effect of trimethylgallic acid esters against chronic stress-induced anxiety-like behavior and oxidative stress in mice

BackgroundMany studies have shown that the levels of oxidative stress (increased lipid peroxidation, decreased glutathione levels and endogenous antioxidant enzyme activities) and proinflammatory cytokines (e.g., TNF-α) are increased in patients with chronic fatigue syndrome. Gallic acid and other phenolic compounds are potent antioxidants and inhibitor of cytokine production. The present study was designed to investigate the effect of newly synthesized conjugated esters of trimethylgallic acid in an experimental model of chronic stress.MethodsThe animals were forced to swim individually for a period of 6 min every day for 15 days to induce chronic stress. The locomotor activity, anxiety-like behavior, and memory retention were evaluated in chronically stressed animals, followed by biochemical estimations and neuroinflammatory surge in the brain.ResultsChronic treatment with trimethylgallic acid esters for 15 days significantly reversed the chronic stress-induced behavioral (impaired locomotor activity, anxiety-like behavior, and decreased percentage of memory retention), biochemical (increased lipid peroxidation and nitrite levels; decreased glutathione levels, superoxide dismutase and catalase activities), and inflammation surge (serum TNF-α) in stressed mice.ConclusionsThe study revealed that trimethylgallic acid esters could ameliorate chronic stress-induced various behavioral and biochemical alterations in mice, showing protective effects against chronic stress.     

Long-term changes in fear conditioning and anxiety-like behavior following nicotine exposure in adult versus adolescent rats

Adolescent nicotine exposure is associated with long-term use, and it has been suggested that this vulnerability to addiction may relate to lasting anxiogenic effects of the drug. However, few studies have addressed long-term effects of adolescent nicotine, and fewer yet have compared adolescent to adult exposure. Male and female Long-Evans rats continuously received nicotine bitartrate or sodium tartrate via osmotic mini-pumps over 15 days either during adolescence (p28-42) or adulthood (p85-99). Initial nicotine dose (free base) was either low (1 mg/kg/day) or high (2 mg/kg/day). Open field behavior and fear conditioning were assessed in adulthood, 1 month post-dosing. Animals pretreated with nicotine during adolescence showed less center time in a novel open field than sham controls. Conversely, the two nicotine doses differentially affected fear conditioning. Animals pretreated with low nicotine during adolescence demonstrated superior acquisition of the task compared to sham control animals; however, unlike either high nicotine-pretreated or sham control animals, they failed to extinguish the learned behavior. In contrast, animals pretreated during adulthood did not behave significantly different from sham controls on either task. Overall, nicotine-pretreatment during adolescence induced effects on behaviors related to fear and anxiety in adulthood, while comparable pretreatment during adulthood failed to produce significant residual effects.     

Acute handling stress downregulates benzodiazepine receptors: Reversal by diazepam

In rats naive to handling, the effects of an acute handling stress led to lower [³H]flunitrazepam binding in the frontal cortex, compared with animals previously habituated to handling for 2 or 21 days. This decreased binding was due to reductions in the number of receptors, not to a change in affinity. Pre-incubation with diazepam (0.3, 3.0 or 30 μM) of frontal cortex homogenates taken from naive rats exposed to acute handling stress (followed by extensive washing to remove residual diazepam and endogenous modulators) led to a concentration-dependent increase in the number of benzodiazepine receptors, without any change in K_D. Acute in vivo administration of diazepam (4 mg/kg) prior to the handling stress was without significant effect in handling-habituated animals, but increases [³H]flunitrazepam binding in handling naive rats. Thus, handling habituation and diazepam treatment have similar actions on benzodiazepine binding and represent two ways of adapting to the stress of handling by increasing the number of benzodiazepine receptors.     

地西泮注射液致小儿哮喘严重发作

患儿,2岁4个月,右侧腹股沟斜疝嵌顿12h,拟在全麻下行疝松解、疝内容物回纳、疝囊高位结扎、修补术。检查:体重13kg,心率105次/min,律齐,呼吸22次/min、双肺呼吸音清晰,双侧阴囊高度肿胀,以右侧明显,患儿哭闹不止。入室前肌注鲁米那40mg、阿托品0.3mg,入室后给氧、ASC-553监护仪监护:SPO2:98%、HR:108次/min。给地西泮(安定)注射液2.5m g稀释静脉诱导,推完药物后患儿突然出现剧烈咳嗽、口唇发绀,呼吸困难,明显喘鸣音,心率增快至180次/min,SPO2下降至50%。立即面罩加压给氧、地塞米松5mg(入莫菲氏管),缺氧症状缓解(SPO2上升至80%～85%),…     

Establishment of a diazepam preference in human volunteers following a differential-conditioning history of placebo versus diazepam choice

This study examined whether preference for a drug (diazepam or placebo) could be switched using conditioning procedures. During the first 4 sessions of Phase 1, 6 participants received 5 mg of diazepam or placebo under double-blind conditions. During the remaining 5 sessions of Phase 1, participants selected the drug they wished to receive. The first 4 sessions of Phase 2 were a replication of Phase 1, except that following ingestion of the drug, participants completed a computer task for which they could earn money. Payment for the computer task was lowest following ingestion of the drug they preferred in Phase I and highest following the drug they had avoided. Preference was reassessed during the last 5 sessions of Phase 2. Five of the participants preferred placebo in Phase 1 but diazepam in Phase 2. Subjective responses to the drugs also changed across the 2 phases.     

Acceleration by stress of dopamine synthesis and metabolism in prefrontal cortex: Antagonism by diazepam

Summary Using liquid chromatography and electrochemical detection (LCEC), we have measured the accumulation of 3,4-dihydroxyphenylalanine (DOPA) (after L-aromatic amino acid decarboxylase inhibition), dopamine (DA) and 3,4-dihydroxyphenylacetic acid (DOPAC) in the frontal cortex and in the corpus striatum of the rat. Mild-footschock stress increased frontal cortex DOPA accumulation, as well as DA and DOPAC, without changing the concentration of these substances in the corpus striatum. The increases in cortical DA synthesis and metabolism were antagonized by diazepam which, given alone, tended to decrease DOPA accumulation to a small degree. In addition, we have measured the indoles serotonin (5-HT) and its metabolite 5-hydroxyindoleacetic acid (5-HIAA), and the noradrenergic metabolite MHPG, none of which were altered by stress. The accumulation of 5-hydroxytryptophan (5-HTP) was also unaffected by stress but, like DOPA accumulation, was reduced to a small degree by diazepam.This study directly demonstrates a selective activation of frontal cortex catechol synthesis (in vivo tyrosine hydroxylation) by a mild stress, which did not significantly alter cortical noradrenergic or serotonergic metabolism.     

Activity in a modified open-field apparatus: effect of diazepam and prenatal stress

We examined the effect of prenatal stress exposure on sensitivity to diazepam. The stress exposure consisted of handling pregnant rats 5 minutes daily from the 14th to 21st day of gestation. Male offspring were tested at 60 days of age in a modified open-field apparatus 30 minutes after injection with diazepam (0, 1, 5 mg/kg). The 5 mg/kg dose of diazepam depressed the frequency and duration of crossover, rearing, headpoke and corner activities. Rearing was not affected by the 1 mg/kg dose of diazepam. Defecation was increased by the 1 mg/kg dose, but was decreased by 5 mg/kg of diazepam. Prenatal stress exposure altered responsiveness to diazepam on only crossover activity and on defecation. Prenatally stressed animals exhibited an increase in crossover at the low dose of diazepam, while control offspring were insensitive to this dose level. Also, there were more boli in prenatally stressed rats treated with 1 mg/kg diazepam, while the 5 mg/kg dose of the drug decreased the number of boli. The other measures showed a trend in the same direction but the differences were not statistically significant. Thus our results indicate that prenatal stress has very specific effects on the sensitivity of adult offspring to diazepam.