Adrenocortical function of Arctic-breeding glaucous gulls in relation to persistent organic pollutants

Unpredictable changes in the environment stimulate the avian hypothalamo-pituitary-adrenal axis to produce corticosterone, which induces behavioural and metabolic changes that enhance survival in the face of adverse environmental conditions. In addition to profound environmental perturbations, such as severe weather conditions and unpredictable food shortages, many Arctic-breeding birds are also confronted with chronic exposure to persistent organic pollutants (POPs), some of which are known to disrupt endocrine processes. This study investigated the adrenocortical function of a top predator in the Arctic marine environment, the glaucous gull (Larus hyperboreus). High concentrations of organochlorines, brominated flame retardants and metabolically-derived products in blood plasma of incubating glaucous gulls were associated with high baseline corticosterone concentrations in both sexes and a reduced stress response in males. Contaminant-related changes in corticosterone concentration occurred over and above differences in body condition and seasonal variation. Chronically high corticosterone concentrations and/or a compromised adrenocortical response to stress can have negative effects on the health of an individual. The results of the present study suggest that exposure to POPs may increase the vulnerability of glaucous gulls to environmental stressors and thus could potentially compromise their ability to adapt to the rapidly changing environmental conditions associated with climate change that are currently seen in the Arctic.     

Physiological stress in captive Greater rheas (Rhea americana): Highly sensitive plasma corticosterone response to an ACTH challenge

Up to the present no studies have been conducted either on baseline concentrations of adrenal hormones or on hormonal responses to stress in Greater rhea (Rhea americana) and most ratite species. The aims of this work were to assess the presence of corticosterone in plasma of Greater rhea, to validate a corticosterone ¹²⁵I-radioimmunoassay for determining corticosterone levels in plasma samples and to study the activation of the adrenal gland after an adrenocorticotrophic hormone (ACTH) challenge. Six captive Greater rhea juveniles of 10 months of age received an intravenous ACTH injection. Blood samples were taken at 0 min (baseline pre-ACTH levels), and post-injection at 15, 30, 60 min and at 24 and 48 h. The high pressure liquid chromatography (HPLC) analysis of pooled plasma showed that corticosterone is the glucocorticoid found in the plasma of Greater rhea. Biochemical assays of standard validation (e.g., parallelism, exogenous corticosterone recovery) showed that measurements of corticosterone present in the plasma of the Greater rhea provided by commercial corticosterone ¹²⁵I-radioimmunoassay were accurate and precise. ACTH challenge induced a more than 40-fold increase in plasma corticosterone at 60 min post-ACTH (from 4.0 to 166.5 ng/ml, on average). The corticosterone response to ACTH in Greater rhea was higher than is usual in birds, an apparently typical characteristic of ratites.     

健脾益气对神经内分泌免疫网络影响的实验研究

为了观察健脾益气对神经内分泌免疫网络的调节作用，本实验用皮质酮（１０ｍｇ／ｋｇ）造成大鼠下丘脑—垂体—肾上腺—胸腺（ＨＰＡＴ）轴抑制模型，观察健脾益气代表名方四君子汤（ＳＪ）对ＨＰＡＴ轴的影响。结果表明皮质酮大鼠下丘脑单胺类递质的含量明显增高，血浆ＡＣＴＨ、ＣＯＲＴ含量明显降低，体内与体外淋巴细胞增殖反应明显受抑，自然杀伤细胞活性下降，淋巴细胞诱生的ＩＬ—２和γ—ＩＦＮ水平明显降低。２００％四君子汤灌胃（１０ｇ／ｋｇ）能有效改善神经和免疫功能，而对内分泌系统作用不明显。桃红四物汤（ＴＨ）对皮质酮大鼠ＨＰＡＴ轴无影响     

Impact of life-long macronutrient choice on neuroendocrine and cognitive functioning in aged mice: differential effects in stressor-reactive and stressor-resilient mouse strains

Nutrient selection emerges as a result of both genetic and environmental factors and may be further modified by stressors. The impact of this complex interrelationship on pathological outcomes is poorly understood. In the present investigation the stressor-reactive BALB/cByJ and the relatively stressor resilient C57BL/6ByJ mice were maintained on a macronutrient selection protocol or given free access to chow for 20 months. The C57BL/6ByJ mice exhibited a marked preference for fat over carbohydrates, whereas BALB/cByJ mice preferred carbohydrates over fat. Cognitive testing in a Morris water maze indicated that while BALB/cByJ mice were clearly more impaired in this task relative to their C57BL/6ByJ counterparts, there was no substantial effect of the diet at either 13 or 19 months of age. Furthermore, despite their stressor resiliency, at 19 months of age, C57BL/6ByJ mice who invariably consumed fat, exhibited greater plasma corticosterone responses to a 20-min period of restraint than chow fed animals. Indeed, the corticosterone rise was as pronounced as in the more reactive BALB/cByJ strain. Furthermore, the C57BL/6ByJ diet-fed mice showed features of insulin insensitivity and increased adiposity. These data suggest that the adverse effects of fat consumption need to be considered in the context of genetically determined vulnerability/resilience factors.     

Prenatal stress in rats predicts immobility behavior in the forced swim test. Effects of a chronic treatment with tianeptine

Prenatally-stressed (PS) rats are characterized by a general impairment of the hypothalamo-pituitary-adrenal (HPA) axis and sleep disturbances indicating that this model has face validity with some clinical features observed in a subpopulation of depressed patients. The prolonged corticosterone secretion shown by PS rats in response to stress was positively correlated with an increased immobility behavior in the forced swim test. To investigate the predictive validity of this model, a separate group of animals was chronically treated with the antidepressant tianeptine (10 mg/kg i.p. for 21 days). Such chronic treatment reduced in PS rats immobility time in the forced swim test. These findings suggest that the PS rat is an interesting animal model for the evaluation of antidepressant treatment.     

Evaluation of the effects of chronic mild stressors on hedonic and physiological responses: sex and strain compared

The chronic mild stress (CMS) paradigm was developed in order to simulate in animals the symptom of anhedonia, a major feature of depression. Typically, changes in hedonic status are interpreted from a decrease in either intake or preference for a mild sucrose solution. Although the incidence of clinical depression is significantly higher in women than in men, the study of this disorder in most animal models of depression has been based on the responses of male rodents. The purpose of this study was to compare the effects of 6 weeks of CMS administration among male and female rats of two rat strains, Sprague-Dawley (SD) and Long Evans (LE), with respect to physiological (body, adrenal gland, and spleen weight) and biochemical (plasma corticosterone levels) indices of stress as well as evaluations of 1 and 24 h sucrose intake and preference. Estrous cycle was tracked throughout the study. Overall, our results indicate a slower rate of weight gain in animals, greater in males, exposed to the chronic stressor regime. Furthermore, CMS is shown to disrupt estrous cycling, predominantly in the Long Evans strain of rats. The main behavioral finding was a significant reduction in 24 h sucrose intake in female treated groups, which was not accompanied by alterations in preference. Corticosterone levels were elevated in CMS-treated animals relative to the singly housed control groups, but exposure to a subsequent stressor was not influenced by the stress history. Taken together, the effects of chronic stressor exposure are evident, based on physiological and biochemical indices, although none of the measures distinguished any striking gender specific reactions. The usefulness of sucrose intake or preference as behavioral indices of CMS-induced anhedonia in males and females is modest at best.     

电针对类风湿关节炎大鼠糖皮质激素及受体的影响

目的 :探讨电针对类风湿性关节炎 (RA)大鼠糖皮质激素 (CS)及受体 (GCR)的影响。方法 :采用佐剂性关节炎大鼠 (AA)作为RA动物模型 ,电针“足三里”治疗后 ,放免测定血浆CS、胸腺GCR含量。结果 :模型组大鼠血浆CS明显下降 ,电针后CS水平明显升高 ,二者比较 ,P <0 .0 5,且达到正常水平 ,电针组与正常组比较 ,P >0 .0 5;模型组大鼠胸腺GCRKD值显著低于正常组和空电组 (P <0 .0 1 ) ,其浓度也明显低于正常组、空电组 (P <0 .0 5) ,电针治疗后GCRKD值和浓度水平与模型组相比均有显著提高 (P <0 .0 1 )。结论 :电针能够增加RA大鼠的CS、GCR含量水平     

Endogenous gonadal hormones modulate behavioral and neurochemical responses to acute and chronic cocaine administration

Recent evidence demonstrates that there are sex differences in behavioral responses to cocaine. Further, reproductive gonadal hormones (estrogen, progesterone and testosterone) have been further implicated in mediating some of the cocaine-induced alterations. To better understand sex differences and the role of gonadal hormones in cocaine-induced locomotor and stereotypic behavior, intact and gonadectomized male and female Fischer rats were randomly assigned to either chronic cocaine (15 mg/kg) or saline treatments for 14 days followed by a challenge administration (7 days after the last cocaine/saline administration). Locomotor (ambulatory and rearing) and stereotypic activities were measured on days 1, 7 and 14 as well as after withdrawal/challenge with cocaine. Overall, intact female rats consistently showed a rapid (acquired by day 7) and longer lasting (persistent through the challenge dose) sensitization for all locomotor behaviors than any of the other groups. In contrast, intact males developed sensitization of these locomotor activities only in response to chronic cocaine administration, and after withdrawal and drug challenge the sensitization to cocaine-induced locomotor activity was no longer present. In female rats, gonadectomy affected ambulatory activity but not total and rearing responses after acute, sub-acute, chronic and challenge response to cocaine. On the other hand, castrated male rats were affected in cocaine-induced ambulatory activity but not rearing activity. In intact male rats, cocaine-induced stereotypic activity was rapidly and persistently sensitized after 7 days of cocaine administration, where gonadectomized male rats developed sensitization to cocaine-induced stereotypic activity only after a challenge cocaine administration. Although cocaine induced stereotypic activity, no statistically significant differences were observed between intact and ovariectomized female rats or throughout the different lengths of cocaine administration. After a challenge of cocaine, corticosterone levels were induced in all experimental groups. Moreover, no differences in levels of benzoylecgonine, a cocaine metabolite, were observed. Similar to our previous observations after acute cocaine administration, after challenge of cocaine, an increase in progesterone and a decrease in testosterone levels were observed in intact females and males, respectively. In summary, endogenous hormones seem to be involved in the behavioral activation and development of sensitization to cocaine.     

强迫游泳应激大鼠行为和血清皮质酮的变化

目的探讨强迫游泳不同应激阶段和应激强度对大鼠行为和内分泌的影响,并分析这些改变的精神病理学意义。方法建立强迫游泳模型,将大鼠随机分为对照组、单次应激组、2周应激组和4周应激组。采用旷场试验评定应激后大鼠的行为反应,酶联免疫吸附实验检测血清皮质酮水平。结果随着应激次数增加,大鼠的主动性运动逐渐减少,而被动性运动逐步增加。单次应激组的直立和修饰[(7.50±2.04)次,(8.33±1.88)次]明显高于对照组[(1.84±0.35)次,(5.05±0.88)次]、2周应激组[(2.54±0.66)次,(4.21±0.37)次]和4周应激组[(2.83±0.75)次,(3.61±0.46)次]。2周应激组和4周应激组血清皮质酮水平[(1001.35±202.91)ng.ml-1,(728.67±250.87)ng.ml-1]明显高于对照组[(626.52±349.89)ng.ml-1]和单次应激组[(359.09±164.32)ng.ml-1]。血清皮质酮水平与应激强度呈正相关(r=0.488,P<0.05)。应激适应组修饰、直立的次数[(6.11±5.04)次,(5.67±4.92)次]明显高于非适应组[(3.64±1.96)次,(1.64±1.06)次]而其皮质酮水平[(580.43±383.52)ng.ml-1]明显低于非适应组[(812.32±157.80)ng.ml-1]。结论(1)单次应激组大鼠表现焦虑样行为增多,慢性应激可导致大鼠行为的明显抑制;(2)在强迫游泳实验中存在主动性与被动性行为个体差异,具有不同的精神病理学意义。     

噻奈普汀对强迫游泳应激大鼠行为及血清皮质酮的影响

目的探讨应激导致大鼠行为和血清皮质酮浓度的改变以及噻奈普汀的抗抑郁机理。方法将24只大鼠随机分为对照组、4周应激组、4周应激给水组和4周应激给药组,各应激组大鼠连续给予强迫游泳试验4周,每天持续15min。游泳后给予灌胃,4周应激给药组按50mg/kg给予噻奈普汀生理盐水溶液灌胃,4周应激给水组按相同比例给予生理盐水灌胃,采用Open-Field法评定行为,使用酶联免疫吸附测定法(ELISA)测定血清皮质酮水平。结果应激后对照组爬格数明显高于4周应激组和4周应激给水组(47.50±29.66)次,(12.67±11.38)次,P(0.05;(47.50±29.66)次,(7.67±3.01)次,P(0.05),而与4周应激给药组比较差异无显著性(P>0.05);对照组大鼠修饰次数明显高于4周应激组和4周应激给水组[(7.00±1.79)次,(2.50±2.35)次,P(0.05;(7.00±1.79)次,(3.17±3.19)次,P(0.05],而与4周应激给药组相比差异无显著性(P>0.05)。对照组血清皮质酮明显低于其他3组(P(0.01)。结论应激可以导致大鼠焦虑样行为增加和皮质酮激素水平升高,噻奈普汀可以有效减少应激所致焦虑样行为。