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Food availability. --- Food. --- Foraging. --- Predation. --- Rat. --- Risk.

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The experience of a single threatening situation may alter the behavior of an animal in a long-lasting way. Long-lasting changes in behavior have been induced in laboratory animals to model and investigate the development and neural substrate of human psychopathologies. Under natural conditions, however, changes in behavior after an aversive experience may be adaptive because behavioral modifications allow animals to adjust to a threat for extended periods of time. In the laboratory setting, properties of the aversive situation and the potential of the animal to respond to the threat may be altered and lead to extensive, prolonged changes, indicating a failure in behavioral regulation. Such long-term changes seem to be mediated by neuronal alterations in components of the fear pathway. To understand psychopathologies, determinants of exaggerated responsivity and the underlying molecular and neural processes have to be analyzed in a comparative way under conditions that produce normal and abnormal fear and anxiety. (C) 2003 Elsevier Ltd. All rights reserved

Adaptation. --- Animal. --- Animals. --- Anxiety-like behavior. --- Anxiety. --- Behavior. --- Brain. --- Cat odor. --- Central-nervous-system. --- Corticotropin-releasing hormone. --- Development. --- Environmental enrichment. --- Experience. --- Exposure. --- Failure. --- Fear. --- Human. --- Laboratory animals. --- Laboratory environment. --- Laboratory-animals. --- Laboratory. --- Long-term changes. --- Long-term. --- Mammalian predators. --- Model. --- Natural. --- Neuronal. --- Nmda receptors. --- One-trial-learning. --- Periods. --- Posttraumatic-stress-disorder. --- Predation. --- Psychopathology. --- Regulation. --- Risk allocation hypothesis. --- Time.

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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.