Chronic unpredictable stress enhances cocaine-conditioned place preference in type 1 cannabinoid receptor knockout mice

Cannabinoid signaling via the type 1 cannabinoid (CB1) receptor modulates the effects of drugs of abuse and the response to exposure to stressors. In addition, exposure to stressors can alter the effects of drugs of abuse. This study examined the effects of exposure to chronic unpredictable stress (CUS) in CB1 receptor knockout (CB1 KO) mice and their wild-type (WT) littermates, using cocaine-conditioned place preference (CPP) to compare their response to cocaine. Mice were untreated or exposed to 2 weeks of CUS. After this period, the acquisition of a cocaine CPP was examined with one of three doses (3.2, 10.0, or 17.0 mg/kg) of cocaine. Untreated CB1 KO and WT mice both acquired the cocaine CPP; however, exposure to CUS enhanced the acquisition of the cocaine CPP in CB1 KO mice, but did not significantly alter the effects of cocaine in WT mice. Taken together, these findings support earlier evidence suggesting a role for the CB1 receptor in the response to stress as well as in the effects of cocaine.     

Attenuation of sucrose consumption in mice by chronic mild stress and its restoration by imipramine

Chronic exposure to mild unpredictable stressors (CMS) has previously been found to reduce the consumption of palatable, sweet solutions in rats. In the present study, the utility of this procedure was assessed in mice. Male AP mice subjected to CMS showed reduced consumption of a 2% or 4% sucrose solution. This effect was reversed by chronic (3 weeks) treatment with the tricyclic antidepressant imipramine (20 mg/kg per day). These results extend previous reports of a generalized decrease in sensitivity to reward (anhedonia) in rats caused by CMS and the efficacy of antidepressant treatment in this paradigm. Chronic unpredictable mild stress in mice appears to provide a realistic animal model of depression.     

Nephrotoxicity and its prevention by taurine in tamoxifen induced oxidative stress in mice

Tamoxifen (TAM) is an anti-neoplastic drug used for the treatment of breast cancer. It decreases the hexose monophosphate shunt and thereby increasing the incidence of oxidative stress in cells leading to tissue injury. The present study was undertaken to investigate modulatory effects of taurine on the nephrotoxicity of TAM with special reference to protection against disruption of nonenzymatic and enzymatic antioxidants. Oxidative stress was measured by renal lipid peroxidation (LPO) level, protein carbonyl (PC) content, reduced glutathione (GSH), activities of phase I and II drug metabolizing and antioxidant enzymes. TAM treatment resulted in a significant (P < 0.001) increase in LPO in kidney tissues as compared to control, while taurine pretreatment showed a significant decrease (P < 0.01) in the LPO in kidneys when compared with the TAM-treated group. Taurine + TAM group animals showed restoration in the level of cytochrome P450 content, activities of glutathione metabolizing enzymes viz., glutathione-S-transferase, glutathione peroxidase, glutathione reductase, glucose-6-phosphate dehydrogenase. Pretreatment of animals with taurine markedly attenuated, PC content, restored the depleted nonenzymatic and enzymatic antioxidants. These results clearly demonstrate the role of oxidative stress, and suggest a protective effect of taurine on TAM-induced nephrotoxicity in mice.     

Effect of imipramine on the expression and acquisition of morphine-induced conditioned place preference in mice

The effect of imipramine and alpha-adrenoceptor agonists and antagonists on the acquisition or expression of morphine-induced conditioned place preference (CPP) was studied in mice. An unbiased CPP paradigm was used to study the effect of the agents. In the first set of experiments, the drugs were used during the development of CPP by morphine or they were used alone in order to see if they induce CPP or conditioned place aversion (CPA). Our data showed that intraperitoneal injection of morphine sulphate (2.5-10 mg/kg) induced CPP in mice. Imipramine (0.5-2.5 mg/kg), phenylephrine (0.5-2 mg/kg), yohimbine (0.5-2 mg/kg) or prazosin (0.1-1 mg/kg) did not influence CPP, but clonidine (0.002-0.05 mg/kg) induced CPA. Yohimbine increased, while clonidine and prazosin reversed, morphine-induced CPP. Phenylephrine did not influence the CPP induced by morphine. In the second set of experiments, when the drugs were used before testing on Day 6, in order to test their effects on the expression of morphine-induced CPP, imipramine (0.5-5 mg/kg) reversed morphine-induced CPP and this reversal was blocked by naloxone (2 mg/kg). Clonidine and prazosin reversed, while yohimbine decreased morphine-induced CPP. Phenylephrine did not alter the morphine response. Furthermore, yohimbine and prazosin reversed the imipramine effect. None of the drugs influenced locomotion. However, prazosin or yohimbine in combination with morphine altered locomotor activity during the acquisition of CPP. Yohimbine by itself increased locomotion. It is concluded that imipramine can induce CPA through an opioid receptor mechanism and alpha-adrenoceptor agents may influence morphine CPP.     

Influence of zinc supplementation on imipramine effect in a chronic unpredictable stress (CUS) model in rats

Zinc is an endogenous modulator of neuronal activity and may play an important role in the pathogenesis of depression. Recent studies have shown that zinc exhibits antidepressant-like activity in some models of depression in rodents. Our previous studies have shown that the footshock-induced fighting behavior was reduced in the rats subjected to chronic unpredictable stress (CUS). This test is used as the new experimental model of depression. Various antidepressant drugs given repeatedly prevented this kind of behavioral depression. The aim of the present study was to evaluate the effect of prolonged treatment with zinc hydroaspartate and to examine if zinc supplementation could modulate the imipramine effect in CUS model of behavioral depression in rats. The experiments were carried out on male Wistar rats. Chronic stress (persisting for 16 days) was induced by the modified method described by Katz et al. Zinc hydroaspartate at the dose of 30 mg/kg/day or 15 mg/kg/day and imipramine at the dose of 5 mg/kg/day were administered once daily for 14 days. Imipramine was given (ip) 1 h before every stress session and zinc hydroaspartate (ip) l h before the antidepressant. The footshock-induced fighting behavior test was performed 48 h after the last session of the chronic stress. It was demonstrated that in chronically stressed rats the number of fighting attacks was significantly reduced (by about 75%). Zinc hydroaspartate at the dose of 30 mg/kg/day, given alone, prevented the deficit in fighting behavior in chronically stressed rats. Neither imipramine at the dose of 5 mg/kg/day nor zinc hydroaspartate (15 mg/kg/day) administered alone changed the intensity of fighting behavior in chronically stressed rats. However, when imipramine was given at the same dose in the rats pretreated with zinc hydroaspartate (15 mg/kg/day) the deficit of fighting behavior was not observed. The present results indicate that zinc similarly to antidepressants protects the rats against the CUS-induced behavioral depression. Moreover, our findings suggest that zinc supplementation could potentiate the antidepressant effect of imipramine.     

隐丹参酮对慢性不可预见应激联合脂多糖所致抑郁小鼠氧化应激和炎症反应的影响

目的 观察隐丹参酮对慢性不可预见应激（CUMS）联合脂多糖（LPS）所致抑郁小鼠氧化应激和炎症反应的影响。方法 60只清洁级ICR小鼠随机分为对照组、模型组、帕罗西汀组（20 mg/kg）及隐丹参酮低、中、高剂量（10、20、40 mg/kg）组,每组10只。采用CUMS＋LPS应激刺激14 d建立抑郁模型（除对照组）,同时ig相应药物或生理盐水,1次/d,连续14 d。通过体质量增量、糖水偏好指数、悬尾实验及新奇环境摄食测试评价抑郁行为,并测定各组血清超氧化物歧化酶（SOD）、过氧化氢酶（CAT）、谷胱甘肽过氧化物酶（GSH-Px）、丙二醛（MDA）,海马和皮质白细胞介素（IL）-6、IL-1β、肿瘤坏死因子（TNF）-α变化情况。结果 隐丹参酮20、40 mg/kg组体质量增量及SOD、CAT、GSH-Px酶活性高于模型组,不动时间短于模型组（P＜0.05、0.01）,海马IL-6、海马和皮质IL-1β含量低于模型组（P＜0.05、0.01）。各治疗组糖水偏好指数高于模型组、摄食潜伏期短于模型组（P＜0.05、0.01）,血清MDA、皮质TNF-α含量低于模型组（P＜0.05、0.01）。隐丹参酮40 mg/kg组皮质IL-6、海马TNF-α含量低于模型组（P＜0.01）。结论 隐丹参酮对CUMS联合LPS致小鼠抑郁症状有改善作用,其机制可能与抑制过强的氧化应激反应与神经炎症反应,并减轻神经元损伤有关。     

An animal model of anhedonia: attenuation of sucrose consumption and place preference conditioning by chronic unpredictable mild stress

Chronic exposure to very mild unpredictable stress has previously been found to depress the consumption of, and preference for, highly palatable sweet solutions. The present study used the place conditioning procedure to investigate whether these effects result from a decreased sensitivity to reward. Rats were subjected to chronic mild unpredictable stress for a total of 4 weeks. During weeks 3 and 4, they received four training trials, in which rewards were presented in a distinctive environment, and four further non-rewarded trials in a different environment. The rewards used in different experiments were food pellets, dilute (0.7%) and concentrated (34%) sucrose solutions, anddl-amphetamine sulphate (0.5 and 1.0 mg/kg). In all experiments, non-stressed animals showed an increase in preference for the environment associated with reward; in stressed animals, these effects were abolished or greatly attenuated. Chronic unpredictable mild stress, which may be comparable in intensity to the difficulties people encounter in their daily lives, appears to cause a generalized decrease in sensitivity to rewards.     

Behavioral and biochemical evidences for antidepressant-like activity of palmatine in mice subjected to chronic unpredictable mild stress

BackgroundIn the present study, antidepressant-like activity of palmatine was evaluated in unstressed and stressed young male Swiss albino mice.MethodsThe animals were subjected to unpredictable mild stress daily for 21 successive days to induce depression-like behavior. Palmatine (0.25, 0.5, 1 mg/kg, ip) was administered for 21 successive days to unstressed and stressed mice. The antidepressant-like activity was evaluated using the tail suspension test, forced swim test and sucrose preference test.ResultsPalmatine (0.5 and 1 mg/kg, ip) significantly decreased immobility periods of unstressed and stressed mice in the forced swim test and tail suspension test, thus indicating its significant antidepressant-like activity. Only the highest dose (1 mg/kg) of palmatine significantly reversed the stress-induced decrease in sucrose preference. There was no significant effect on locomotor activity of the mice by palmatine and fluoxetine. The antidepressant-like activity of palmatine was found to be comparable to fluoxetine (10 mg/kg) administered for successive 21 days. Palmatine (0.5 and 1 mg/kg, ip) significantly reversed the stress-induced increase in brain catalase levels, MAO-A activity, lipid peroxidation, plasma nitrite and corticosterone levels.ConclusionsPalmatine showed significant antidepressant-like activity in unstressed and stressed mice probably through inhibition of MAO-A activity, decrease in plasma nitrite levels and due to its antioxidant activity. In addition, palmatine also showed antidepressant-like activity in stressed mice probably through decrease in plasma corticosterone levels.     

Effect of imipramine on brain D-1 and 5-HT-2A receptors in a chronic unpredictable stress model in rats

Chronic unpredictable stress (CUS) model of depression is one of the well validated animal models of depression. In this paper, we report the results of investigations into dopaminergic D-1 and serotonergic 5-HT-2A receptors in the brain of rats subjected to CUS procedure and treated chronically with imipramine. We have examined the dopaminergic D-1 ([3H-SCH 23390) in the limbic area and serotonergic 5-HT-2A ([3H-ketanserin) receptors in the cerebral cortex by a saturation radioligand binding method in rats subjected to CUS paradigm, imipramine, both CUS and imipramine and control animals. CUS procedure resulted in a significant 36% increase in the D-1 receptor density in the limbic system, which was attenuated by chronic imipramine treatment. Also a 21% increase in the density of 5-HT-2A receptors in the cerebral cortex induced by CUS was reduced by chronic imipramine treatment. The present data indicate that the increases in the density of brain D-1 and 5-HT-2A receptors of rats subjected to CUS, which are "normalized" by imipramine, might be involved in the pathophysiology of "animal depression" (and, thus, in pathophysiology of human depression) and in the mechanism of antidepressant therapy.     

木兰花碱减轻慢性应激小鼠抑郁样行为及对脑部LSD1组蛋白修饰的影响

目的 探索木兰花碱对慢性不可预见性温和应激所致抑郁小鼠行为学的影响机制。方法 将 ICR小鼠随 机分为正常对照组（control组）、抑郁模型组（PG组）、木兰花碱高剂量组（MH组）和木兰花碱低剂量组（ML组）。采用 慢性不可预见性温和刺激方法建立抑郁小鼠模型,检测各组小鼠行为学的变化,并用实时定量 PCR、Western blot检 测小鼠脑部赖氨酸特异性组蛋白去甲基化酶 1（LSD1）mRNA及蛋白表达水平的变化。免疫组化染色法检测小鼠脑 部 LSD1阳性细胞数量。结果 木兰花碱在行为学上改善了小鼠的抑郁状况,与 PG组相比,MH组和 ML组悬尾不动 时间、强迫游泳不动时间明显缩短（P＜0.05）。实时定量 PCR及 Western blot结果显示,与 control组相比,PG组 LSD1 mRNA表达差异无统计学意义,蛋白表达明显降低（P＜0.05）,ML组 LSD1 mRNA和蛋白表达明显升高（P＜0.05）;与 PG组相比,ML组 LSD1 mRNA和蛋白表达明显升高（P＜0.05）。免疫组化结果显示,与 control组相比,PG组小鼠脑部 LSD1阳性细胞数量减少,而 ML组较 PG组增加。结论 在木兰花碱治疗抑郁小鼠的过程中,LSD1可能起到了重要 的调节作用。     

五味子不同炮制品对小鼠慢性不可预知性应激抑郁的改善作用

目的评价五味子不同炮制品对小鼠慢性不可预知性应激抑郁的改善作用。方法 ICR小鼠随机分为对照组、模型组、氟西汀组以及生五味子组、酒五味子组、醋五味子组,每组10只。对照组和模型组ig蒸馏水,氟西汀组ig盐酸氟西汀分散片3.3 mg/kg,生五味子、酒五味子和醋五味子组均ig相应药物1.0 g/kg,体积为10 m L/kg,给药1 h后采用10种刺激方法建立慢性不可预知性应激模型,持续28 d。以敞箱实验、悬尾实验、强迫游泳实验进行行为学观察,采用酶联免疫法测定血清中五羟色胺(5-HT)、多巴胺(DA)、肾上腺皮质酮(CORT)水平,对实验结果进行综合分析。结果与模型组比较,生五味子可以增加抑郁小鼠敞箱站立次数(P0.01)、敞箱中央格穿越次数(P0.05),降低悬尾、强迫游泳不动时间(P0.05);酒五味子和醋五味子均对抑郁小鼠敞箱站立次数、敞箱中央格穿越次数无影响,但可降低悬尾不动时间、强迫游泳不动时间(P0.05)。与模型组比较,生五味子可显著升高抑郁小鼠血清中5-HT、DA水平,降低CORT水平(P0.01);酒五味子和醋五味子可显著升高抑郁小鼠血清中DA水平,降低CORT水平(P0.05、0.01),对血清中5-HT水平无影响。结论五味子不同炮制品均有一定的抗抑郁作用,其中生五味子作用较强。     

Changes in analgesia-producing mechanism of repeated cold stress loading in mice

Functional changes in opioid receptors involved in analgesia of repeated cold stress (RCS)-loaded mice were investigated. The antinociceptive potency of morphine (4 mg/kg, PO) was not affected in normal mice by norbinaltorphimine (10 mg/kg, SC), but treatment with this agent resulted in a lower level of morphine-induced antinociception in RCS-loaded animals. The antinociceptive activity of U-50488H (3 mg/kg, SC) was increased in RCS-loaded mice. In contrast to hypersensitivity to U-50488H (1 and 10 microg, IT) noted in RCS-loaded mice, the antinociception induced by DAMGO (0.1 and 1 microg, ICV) was reduced compared to that of normal animals. Diazepam (1 mg/kg/day SC) was given during RCS loading, and this agent prevented the development of hyperalgesia and the decrease in the antinociceptive activity of DAMGO (1 microg, ICV) in RCS-loaded mice, but there was no effect on the enhancement of the antinociceptive potency of U-50488H (10 microg, IT). These results indicate that the RCS-loaded mice were hyposensitive to supraspinal mu-opioid receptor-mediated antinociception, whereas their antinociceptive activities through kappa-opioid receptor in the spinal cord were increased. Hypofunction of the supraspinal mu-opioid receptor due to anxiety may explain the mechanism involved in the lowering of the nociceptive threshold in RCS-loaded animals.     

Social stress is as effective as physical stress in reinstating morphine-induced place preference in mice

Rationale Relapse to drug-seeking in abstinent heroin addicts and reinstatement in experimental animals are observed when exposed to drug-associated stimuli or cues, the drug itself, and stressful events. It has been shown that footshock-induced stress increases the rewarding effects of opiates, delays extinction, and induces the reinstatement of drug-seeking. However, the effects of social stress on the reinstatement of opiate-seeking after extinction has not been studied.Objectives The role of physical (restraint and tail pinch) and social (social defeat) stressors on the reinstatement of morphine-induced conditioned place preference (CPP) was evaluated.Methods Adult male OF1 mice were conditioned with 10, 20, or 40 mg/kg of morphine or saline. Only morphine-conditioned animals acquired CPP. All mice underwent extinction sessions until the CPP was extinguished. Then, the effects of physical or social stress on the reinstatement of CPP were evaluated. Morphine- and saline-conditioned animals were exposed to the respective stressor or control stress condition immediately or 15 min before reinstatement tests. In experiment 1, animals underwent restraint for 15 min. In experiment 2, animals were exposed to tail pinch or placed in a cage without any manipulation for 15 min. In experiment 3, animals performed an agonistic encounter with an isolated or anosmic mouse or were placed in a cage without any social contact or manipulation.Results Restraint, tail pinch, and social defeat in an agonistic encounter with an isolated mouse produce the reinstatement of CPP in morphine-conditioned animals.Conclusions These data demonstrate that social stress is as effective as physical stress in reinstating morphine-seeking.     

艾拉片对重复束缚应激所致勃起功能障碍小鼠的治疗作用

艾拉片是由经典维医方药Majun Mupakhi Ela优化提取制备得到的.该方一直用于阳痿的治疗,但艾拉片的具体适应证和治疗机制尚不清楚.本研究拟探讨艾拉片对重复束缚应激所致勃起功能障碍(ED)小鼠的保护作用及其可能机制.每天将小鼠置于束缚盒中连续14天,并在束缚前1小时给予艾拉片.第14日晚进行交配实验.此后,收集...     

Inhibition of protein synthesis in mice by ochratoxin A and its prevention by phenylalanine

The sensitivity of protein synthesis to ip doses of ochratoxin A ranging from 1 to 15 mg/kg body weight has been determined in the livers, kidneys and spleens of mice. The incorporation of ¹⁴C-labelled amino acids into protein was measured in the total tissue homogenate, in the 105,000-g supernatant fraction and in the fraction of thermostable soluble proteins. The inhibition of protein synthesis was greatest in spleen and kidney and least in liver. The percentage inhibition of protein synthesis by any one dose of ochratoxin A was similar in all of the protein fractions from any one organ. The degree of inhibition of protein synthesis 5 hr after administration of 1 mg ochratoxin A/kg was 26% in liver, 68% in kidney and 75% in spleen. Phenylalanine (100 mg/kg) injected together with ochratoxin A prevented the inhibition of protein synthesis by a dose of 10 mg OTA/kg in all of these organs.     

Alteration of voluntary ethanol and saccharin consumption by the neurosteroid allopregnanolone in mice

RATIONALE: The neurosteroid 3 alpha-hydroxy-5 alpha-pregnan-20-one (allopregnanolone, ALLOP) is a positive modulator of gamma-aminobutyric acid type A (GABA(A)) receptors. Recent findings indicate that ethanol (EtOH) and ALLOP share common mechanisms of action and that ALLOP may modulate some of EtOH's abuse-related effects. OBJECTIVES: The present studies investigated whether ALLOP pretreatment altered voluntary EtOH consumption in male and female C57BL/6J mice, and voluntary saccharin and quinine consumption in male C57BL/6J mice. METHODS: Mice had access to two drinking tubes containing water versus 5% or 10% (v/v) EtOH or a tastant for 2 h each day at the beginning of the dark cycle. Following establishment of stable consumption, animals received 2 days of vehicle followed by 3 days of ALLOP injections (0, 3.2, 10, or 17 mg/kg, IP), immediately prior to EtOH or tastant access. RESULTS: Prior to injection, the 2-h baseline dose of the 10% EtOH solution consumed was 1.31 g/kg (expt 1) or 2.46 g/kg (expt 3) for male and 2.21 g/kg (expt 2) for female mice. Baseline intake of the 5% EtOH solution was 0.60 g/kg for males and 0.75 g/kg for females (expt 5). In males, ALLOP administration significantly and dose-dependently increased consumption of both EtOH solutions during the first hour of availability without affecting water intake. In females, ALLOP did not significantly alter EtOH consumption. Lastly, ALLOP significantly increased saccharin, but not quinine, consumption in males (females were not tested). CONCLUSIONS: ALLOP may increase voluntary EtOH consumption in male mice by altering its reinforcing effects. The lack of significant effect on quinine and water consumption suggests that ALLOP does not simply increase consumption of all fluids.     

Felbamate reduces hormone release and locomotor hypoactivity induced by repeated stress of social defeat in mice.

Glutamatergic neurotransmission plays a role in stress hormone release and the development of mood diseases. The aim of these studies was to verify the hypothesis that repeated treatment with felbamate, an antiepileptic drug modulating glutamatergic neurotransmission, affects hormone release in response to chronic stress. A mouse model of repeated social defeat (nonaggressive male mouse repeatedly defeated by aggressive counterparts) was used. The results showed that acute treatment with felbamate reduced hypolocomotion in an open field induced by repeated social conflict. The same stress procedure resulted in increased release of corticosterone and dopamine. Felbamate decreased noradrenaline concentrations and inhibited stress-induced rise in corticosterone and dopamine. It is suggested that modulation of stress hormone release may be induced by the action of felbamate on glutamate neurotransmission, and neuroendocrine changes could contribute to behavioural effects of the drug. Antidepressant action of this mood-stabilizing drug suggested by clinicians needs further verification.     

Antagonism by d,1-propranolol of imipramine effects in mice

Three agents with known or suspected antidepressant activity, imipramine, salbutamol and dexamphetamine, were active in animal tests predictive of an antidepressant effect in man: antagonism of the hypothermia induced by reserpine, by oxotremorine or by a high dose of apomorphine, and the potentiation of the yohimbine-induced toxicity. These effects were antagonized by d,1-propranolol, suggesting that the stimulation of beta-adrenergic receptors could be a common mechanism underlying their effects. These results agree with the noradrenergic hypothesis of the pathophysiology of affective disorders.     

Nephrotoxicity and its prevention by catechin in ferric nitrilotriacetate promoted oxidative stress in rats

Intraperitoneal injection of ferric nitrilotriacetate (Fe-NTA) to rats and mice results in iron-induced free radical injury and cancer in kidneys. This study was designed to investigate the effect of catechin, a bioflavonoid with antioxidant potential, on Fe-NTA-induced nephrotoxicity in rats. Four groups were employed in the present study. Group I served as control group, Group II animals received Fe-NTA (8 mg iron/kg body weight i.p.), Group III animals were given 40 mg/kg catechin p.o. twice a day for 4 days and on the 5th day Fe-NTA was challenged, and Group IV animals received catechin alone for 4 days. Renal function was assessed by measuring plasma creatinine and blood urea nitrogen. The oxidative stress was measured by renal malondialdehyde levels, reduced glutathione levels and by enzymatic activity of catalase, glutathione reductase and superoxide dismutase. One hour after a single intraperitoneal (i.p.) injection of Fe-NTA (8 mg iron/kg), a marked deterioration of renal architecture, renal function and severe oxidative stress was observed. Pretreatment of animals with catechin markedly attenuated renal dysfunction, reduced elevated thiobarbituric acid reacting substances (TBARS), restored the depleted renal antioxidant enzymes and normalized the renal morphological alterations. These results clearly demonstrate the role of oxidative stress and its relation to renal dysfunction, and suggest a protective effect of catechin on Fe-NTA-induced nephrotoxicity in rats.