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Abstract In the present work we have characterized the long-term influence of a single exposure to the stress of immobilization (IMO) on the hypothalamic-pituitary-adrenal (HPA) axis of adult rats. Rats without prior stress (control) and rats exposed to IMO for 2 h on day 1 (IMO+4wk) or on day 21 (IMO+1wk) were killed on day 28, either without stress (basal), immediately after IMO for 1 h (IMO), or 1 h after termination of IMO (post-IMO). IMO caused a strong activation of c-fos mRNA and corticotropin-releasing factor (CRF) and vasopressin (AVP) heteronuclear RNA (hnRNA) in the paraventricular nucleus of the hypothalamus in control rats; this activation was essentially maintained in the post-IMO period. The overall AVP hnRNA response to day 28 stress was not affected by prior stress. Post-IMO c-fos mRNA and CRF hnRNA levels were lower in previously stressed rats, as compared with controls. Whereas the effect of prior IMO on both peripheral HPA hormones and c-fos mRNA was maximal in IMO+1wk rats, the effect of prior stress on CRF hnRNA was only observed in IMO+4wk rats. The present data indicate that prior single IMO triggers a process of desensitization of the HPA responsiveness to IMO over the course of the following weeks. Although the various components of the HPA axis were modified in the same direction, a clear temporal dissociation was found among them, revealing the fine tuning of stress-induced activation of the HPA axis

Activation. --- Adult rats. --- Adult-rat. --- Adult-rats. --- Adult. --- C-fos. --- Control. --- Corticotropin-releasing factor. --- Corticotropin-releasing-factor. --- Crf. --- Direction. --- Exposure. --- Hormone. --- Hormones. --- Hpa axis. --- Hypothalamic-pituitary-adrenal axis. --- Hypothalamic-pituitary-adrenal. --- Hypothalamus. --- Immobilization stress. --- Level. --- Long-term. --- Nucleus. --- Paraventricular nucleus. --- Rat. --- Rats. --- Response. --- Rna. --- Stress. --- Vasopressin. --- Work.

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Studies of the brain inform us about the cognitive abilities of animals and hence affect the extent to which animals of that species are respected However, they can also tell us how an individual is likely to be perceiving, attending to, evaluating, coping with, enjoying, or disturbed by its environment, and so can give direct information about welfare. In studies of welfare, we are especially interested in how an individual feels. Since this depends upon high-level brain processing, we have to investigate brain function. Brain correlates of preferred social, sexual and parental situations include elevated oxytocin in the para-ventricular nucleus of the hypothalamus. Abnormal behaviour may have brain correlates, for example, high frequencies of stereotypy are associated with down-regulated P and kappa receptors and dopamine depletion in the frontal cortex. Such results help in evaluating the effects of treatment on welfare. Some brain changes, such as increased glucocorticoid receptors in the frontal lobes or increased activity in the amygdala, may be a sensitive indicator of perceived emergency. Active immunological defences lead to cytokine production in the brain, vagal nerve activity and sickness effects. Some aspects of brain function can be temporarily suppressed, for example, by opioids when there is severe pain, or permanently impaired, for example, in severely impoverished environments or during depression. Coping attempts or environmental impact can lead to injury to the brain, damage to hippocampal neurons, remodelling of dendrites in the hippocampus, or to other brain disorganisation. Brain measures can explain the nature and magnitude of many effects on welfare

Ability. --- Abnormal behaviour,adrenal,animal welfare,brain measures,coping,opioids. --- Abnormal behaviour. --- Activity. --- Amygdala. --- Animal welfare. --- Animal-welfare. --- Animal. --- Animals. --- Behavior. --- Behaviour. --- Brain. --- Cognitive-ability. --- Coping. --- Cortex. --- Damage. --- Depression. --- Dopamine. --- Emergency. --- Environment. --- Environments. --- Frequency. --- Frontal cortex. --- Frontal lobes. --- Frontal-cortex. --- Frontal. --- Function. --- Glucocorticoid receptors. --- Glucocorticoid. --- Hippocampal-neurons. --- Hippocampal. --- Hippocampus. --- Hypothalamus. --- Impoverished. --- Injuries. --- Injury. --- Neurons. --- Nucleus. --- Opioid. --- Opioids. --- Oxytocin. --- Pain. --- Paraventricular nucleus. --- Production. --- Receptor. --- Receptors. --- Responses. --- Sexual. --- Sheep. --- Situations. --- Social. --- Sows. --- Stereotypies. --- Stereotypy. --- Stress. --- Systems. --- Treatment. --- Us. --- Welfare.

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Young animals respond to threatening stimuli in an age-specific way. Their endocrine and behavioral responses reflect the potential threat of the situation at a given age. The aim of the present study was to determine whether corticotropin-releasing factor (CRF) is involved in the endocrine and behavioral responses to threat and their developmental changes in young rats. Preweaning 14-day-old and postweaning 26-day-old rats were exposed to two age-specific threats, cat odor and an adult male rat. The acute behavioral response was determined during exposure. After exposure, the time courses of the corticosterone response and of CRF expression in the paraventricular nucleus of the hypothalamus (PVN) and in extrahypothalamic areas were assessed. Preweaning rats became immobile when exposed to cat odor or the male rat, whereas postweaning rats became immobile to cat odor only. Male exposure increased serum corticosterone levels in 14-day-old rats, but cat odor failed to increase levels at either age. Exposure induced elevation of CRF mRNA levels in the PVN that paralleled changes in corticosterone levels. CRF may thus play a role in endocrine regulation and its developmental changes during early life. Neither cat odor nor the adult male altered CRF mRNA levels in the bed nucleus of the stria terminalis (BNST) or the amygdala, but both stimuli increased levels in the hippocampus. Hippocampal CRF mRNA expression levels did not parallel cat odor or male-induced immobility, indicating that CRF is not involved in this response in young rats but may be involved in aspects of learning and memory. (C) 2004 Elsevier Inc. All rights reserved

Adult. --- Age. --- Amygdala. --- Animal. --- Animals. --- Area. --- Bed nucleus. --- Behavioral-responses. --- Cat odor. --- Cat. --- Corticosterone. --- Corticotropin-releasing factor. --- Corticotropin-releasing hormone. --- Corticotropin-releasing-factor. --- Crf. --- Defensive-withdrawal. --- Dentate gyrus. --- Developmental-changes. --- Endocrine. --- Exposure. --- Expression. --- Fear. --- Gene-expression. --- Glucocorticoid. --- Hippocampal. --- Hippocampus. --- Hpa axis. --- Hypothalamus. --- Immature rat. --- Immobility. --- Immobilization stress. --- Increase. --- Learning. --- Level. --- Life. --- Male rat. --- Male. --- Memory. --- Messenger-rna expression. --- Nucleus. --- Odor. --- Paraventricular nucleus. --- Pituitary-adrenal axis. --- Play. --- Predation. --- Rat. --- Rats. --- Regulation. --- Response. --- Responses. --- Serum. --- Stimuli. --- Stria terminalis. --- Time-course. --- Time. --- Ultrasonic vocalization. --- Young-rats. --- Young.