3.0 Gy X线全身照射后对大鼠下丘脑—垂体—肾上腺皮质系统应激反应的影响

本文报道了3.0 GyX线全身照射后1、3日大鼠下丘脑—垂体—肾上腺皮质系统对应激刺激(一侧后肢骨折)的反应性变化。正常大鼠受应激刺激后10min,血浆β—EP、皮质酮、肾上腺和垂体的cAM P及下丘脑M—EnK水平都明显升高,而下丘脑β—EP含量则显著降低。照射后1日未应激组,血浆β—EP、皮质酮和垂体cAMP水平均显著高于正常对照,下丘脑β—EP也明显低于正常对照。照后1日应激组各参数虽明显高于正常对照,但与未应激组相比,除肾上腺cAMP和下丘脑B—EP水平显著升高外,其余各参数均差异不显著。照后3日未应激组,各参数都回降到接近正常水平。照后3日应激与未应激组相比,6项参数有4项显著增高,其余血浆皮质酮和下丘脑B—EP 2项虽有升高但差异不显著。结果表明,3.0GyX射线全身照射基本上未降低机体对应激的适应能力。     

Analgesia and impact induced by anticipation stress: involvement of the endogenous opioid peptide system

Anticipation of an unavoidable painful stimulation, i.e. anticipation stress, induces analgesia. This analgesia may result from activation of the endogenous opioid peptide system as it is blocked by naloxone. The present paper characterizes the anticipation stress further by following the kinetics of the analgesia rise, the impact of the stress on the stress-sensitive organs and the involvement of the endogenous opioid peptide system in the anticipation stress effects. Adult male rats exposed repeatedly to placing into a conditioning box followed by a painful stimulation develop analgesia almost immediately after a transfer to the box. Anticipation acts as a specific trigger, no other side stressor is effective. Anticipation stress has a significant impact on stress-sensitive organs: weights of the adrenals increase while those of the thymus and spleen decrease. These changes are associated with a significant increase of plasma corticosterone. Blockade of the endogenous opioid system by naloxone before the exposure to anticipation stress potentiates these stress-induced impacts, especially the decrease of weight of the thymus. Plasma corticosterone levels are not affected by naloxone. During the anticipation stress, the amount of opioid receptors, i.e. of [3H]naloxone binding sites, in the hypothalamus, but not in the striatum, decreases. The possible biological role of stress-induced activation of endogenous opioid system, namely the maintenance of the intensity of stress reaction within certain limits and thus the prevention of the self-destructive effects of stress reactions, is discussed.     

Developmental stress and lead (Pb): Effects of maternal separation and/or Pb on corticosterone,monoamines, and blood Pb in rats

The level of lead (Pb) exposure in children has decreased dramatically since restrictions on its use were implemented. However, even with restrictions, children are exposed to Pb and still present with cognitive and behavioral deficits. One prominent aspect of the exposome of these children is that many come from low social economic status (SES) conditions, and low SES is associated with stress. In order to compare the combined effects of early stress and Pb, Sprague-Dawley rats were exposed to vehicle or Pb either alone or in combination with maternal separation stress during brain development (i.e., postnatal day (P)4–P11, P19, or P28). Maternally separated/isolated pups had lower body and thymus weights during exposure and had increased levels of blood Pb compared with vehicle controls. Isolation, but not Pb, affected the response to an acute stressor (standing in shallow water) when assessed on P19 and P29, but not earlier on P11. Interactions of Pb and isolation were found on monoamines in the neostriatum, hippocampus, and hypothalamus on turnover but not on levels, and most changes were on dopamine turnover. Isolation had greater short-term effects than Pb. Interactions were dependent on age, sex, and acute stress.     

焦虑大鼠内脏敏感性增高以及行直结肠扩张后血清皮质酮的变化及意义

目的内脏高敏感性是肠易激综合征( 1BS)症状最重要的病理生理机制之一,焦虑可能与内脏高敏的发生密切相关。本研究旨在探讨焦虑对大鼠直结肠敏感性的作用以及血清皮质酮与内脏高敏的关系。方法Wistar大鼠随机分为对照组和焦虑组两组,通过对大鼠行空瓶刺激2周建立以焦虑为主要表现的慢性情绪应激模型。造模期间,观察大鼠的攻击、探究和修饰三种行为,对其进行情绪性行为学分析。造模结束后,以腹部回缩反射(AWR)评分为指标观察大鼠对直结肠气囊扩张(CRD)的反应性,评估内脏敏感性。然后将两组各随机分为扩张组和非扩张组,对扩张组行CRD ,并取血清,对血清皮质酮定量测定。结果空瓶刺激期间,同对照组相比,焦虑组探究、攻击行为明显增多,修饰行为减少(P <0 0 1)。焦虑组在2 0mmHg、40mmHg、60mmHg和80mmHg的扩张压力下的AWR评分均显著高于对照组(P <0 0 1)。焦虑组与对照组相比血清皮质酮水平明显升高(P <0 0 1) ,但各组扩张后皮质酮水平较扩张前仅有轻微升高,无显著差异(P >0 0 5 )。结论焦虑对IBS内脏高敏起一定作用,其发挥作用的机制可能并非单一通过下丘脑_垂体_肾上腺皮质系统(HPA轴)来实现,推测还可能与脑内单胺类神经递质NE浓度的改变有关。     

Effects of comfort food on food intake, anxiety-like behavior and the stress response in rats

It has been suggested that access to high caloric food attenuates stress response. The present paper investigates whether access to commercial chow enriched with glucose and fat, here referred to as comfort food alters behavioral, metabolic, and hormonal parameters of rats submitted to three daily sessions of foot-shock stress. Food intake, anxiety-like behaviors, and serum levels of insulin, leptin, corticosterone, glucose and triglycerides were determined. The rats submitted to stress decreased the intake of commercial chow, but kept unaltered the intake of comfort food. During the elevated plus maze (EPM) test, stressed rats increased the number of head dipping, entries into the open arms, as well as the time spent there, and decreased the number of stretched-attend posture and risk assessment. These effects of stress were independent of the type of food consumed. Non-stressed rats ingesting comfort food decreased risk assessment as well. Stress and comfort food increased time spent in the center of the open field and delayed the first crossing to a new quadrant. Stress increased the plasma level of glucose and insulin, and reduced triglycerides, although consumption of comfort food increases glucose, triglyceride and leptin levels; no effect on leptin level was associated to stress. The stress induced increase in serum corticosterone was attenuated when rats had access to comfort food. It was concluded that foot-shock stress has an anorexigenic effect that is independent of leptin and prevented upon access to comfort food. Foot-shock stress also has an anxiolytic effect that is potentiated by the ingestion of comfort food and that is evidenced by both EPM and open field tests.     

Adrenocortical response to mating, social interaction and restraint in the female Japanese quail

In some species, the act of mating may be the only occasion when a female judges the male and the course of the sexual encounter might influence forms of maternal investment that are mediated by hormonal pathways. Despite the growing interest in fitness consequences of acute adrenocortical responses, it has not been determined to what extent the act of mating provokes such responses in females. We used female Japanese quail (Coturnix japonica) to determine to what extent any increase in corticosterone (CORT) is specific to actually mating with a male compared to visual and auditory contact with a male, and compared to social interaction with a female. We also asked if greater mating experience decreases the CORT response. We assessed how body condition of the individuals and their behavior during testing contributed to the variation in CORT response. As an additional reference for CORT increase we used a restraint procedure which resulted in the highest CORT. Our results show that females mating with a male have plasma CORT concentrations significantly increased from the baseline, which is not the case in females interacting with a male without the possibility of mating. Greater previous mating experience does not affect the CORT change caused by sexual interaction. Interestingly, social interaction with a female elicited a similar CORT response as mating with a male, which suggests that the effect on CORT was due to direct social interactions per se and not specific to the act of mating. Behavior during social and sexual interactions did not predict the CORT response, but larger females exhibited lower baseline and response CORT concentrations. We suggest that the lesser adrenocortical response of larger females might be related to their better control of the course of mating and might help them to adjust their reproductive investment, as reported in earlier studies.     

Environmental and tactile stimulation modulates the neonatal handling effect on adult rat spatial memory

Handling of rat pups promotes their adult cognitive performance. However, new data suggest that individual components of the handling procedure, like exposure to novelty or tactile stimulation, have distinct lasting effects on behaviour. In this study we examined the interaction of early novelty exposure with a varying amount of tactile stimulation on spatial recognition memory and corticosterone secretion of adult male and female rats. A split litter design was used and the experimental animals were also compared to animal facility reared controls. The experiment was conducted in two phases. In the first phase, we examined the effect of novel or home environment during the 15-min of neonatal handling, following 10 back-strokes. Tactile stimulation of 10 back-strokes combined with novelty exposure, enhanced novel arm discrimination in a Y-maze task in adult rats of both sexes compared to their siblings that stayed at home, as well as to the animal facility reared controls. In the second phase, additional back-stroking (total of 20 back-strokes) reduced the Y-maze performance of males neonatally exposed to novelty, while the same treatment enhanced the performance of their siblings that stayed at home. Basal corticosterone levels, determined 1 week post-Y-maze, were significantly increased only in the novelty exposed/10 back-stroked females compared to same sex non-handled controls. In contrast, 10 back-strokes combined with the home cage environment increased corticosterone in males. Increase to 20 back-strokes reversed the impact of neonatal environment on corticosterone levels.     

Re-exposure to endotoxin induces differential cytokine gene expression in the rat hypothalamus and spleen

This study was designed to investigate whether the pattern of hypothalamic and splenic cytokine expression induced by peripheral administration of a bacterial lipopolysaccharide (LPS) is affected by prior exposure to LPS derived from another bacterial strain. Injection of LPS from Salmonella enteritidis (LPS₂) alone resulted in increased hypothalamic gene expression of IL-1β, IL-6, TNFα, IL-1ra and IL-10. However, pre-exposure to LPS derived from Escherichia coli (LPS₁) 3 weeks before, significantly attenuated hypothalamic IL-1ra, IL-6 and IL-10 expression. IL-1β expression also tended to be lower. This pattern contrasted with the robust cytokine expression in the spleen of LPS₂-treated rats previously exposed to LPS₁, since pre-treatment with endotoxin resulted in a significantly greater response of IL-1β and IL-1ra to LPS₂. Expression of TNFα and IL-10 also tended to be higher. Pre-treatment with LPS₁ did not significantly affect the marked increase in corticosterone and adrenaline blood levels induced by LPS₂. Thus, while endotoxin pre-exposure seemed not to induce a “tolerant” state in the periphery as judged by the immune and endocrine parameters evaluated upon re-stimulation, expression of four of the six cytokines measured was decreased in the hypothalamus. This is the first demonstration that endotoxin priming can differentially affect cytokine expression in the central nervous system and peripheral tissues when a host is confronted with a second, acute, pro-inflammatory stimulus. These results may provide new evidence for the involvement of cytokine pathways in the central nervous system in modulating peripheral inflammation and mediating cognitive and behavioural alterations during inflammatory diseases.