Psychoneuroendocrinology
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Psychoneuroendocrinology · Jul 2008
Chronic psychosocial stress affects corticotropin-releasing factor in the paraventricular nucleus and central extended amygdala as well as urocortin 1 in the non-preganglionic Edinger-Westphal nucleus of the tree shrew.
Stressful stimuli evoke neuronal and neuroendocrine responses helping an organism to adapt to changed environmental conditions. Chronic stressors may induce maladaptive responses leading to psychiatric diseases, such as anxiety and major depression. A suitable animal model to unravel mechanisms involved in the control of adaptation to chronic stress is the psychological subordination stress in the male tree shrew. ⋯ In the pPVN, the number of CRF-immunoreactive neurons and the specific signal density of CRF-immunoreactive fiber terminals in the CeA were strongly reduced (-300 and -40%, respectively; P<0.05), whereas no significant difference in CRF fiber density was found in BNSTdl. The npEW revealed 4 times less Ucn1-immunoreactive neurons (P<0.05). These clear effects on both Ucn1- and CRF-neuropeptide contents may reflect a crucial mechanism enabling the animal to adapt successfully to the stressors, and point to the significance of the pPVN, CeA and npEW in stress-induced brain diseases.
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Psychoneuroendocrinology · May 2008
Comparative StudyThe role of the arginine vasopressin Avp1b receptor in the acute neuroendocrine action of antidepressants.
In times of stress the hypothalamic-pituitary-adrenal (HPA) axis is activated and releases two neurohormones, corticotropin-releasing hormone (Crh) and arginine vasopressin (Avp), to synergistically stimulate the secretion of adrenocorticotropin hormone (ACTH) from the anterior pituitary, culminating in a rise in circulating glucocorticoids. Avp mediates its actions at the Avp V1b receptor (Avpr1b) present on pituitary corticotropes. Dysregulation of the stress response is associated with the pathophysiology of depression and a major treatment involves increasing the availability of monamines at the synaptic cleft. ⋯ In contrast, fluoxetine treatment increased PVN Avp mRNA levels in female Avpr1b wild type but not KO animals. PVN Oxt mRNA levels increased in fluoxetine-treated female mice of both genotypes. The data suggests that the Avpr1b is required to drive the HPA axis response to acute antidepressant treatment and provides further evidence of a sexual dichotomy in the regulation of PVN Avp/Oxt gene expression following antidepressant administration.
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Psychoneuroendocrinology · May 2008
Behavioral tolerance to endotoxin is enhanced by adaptation to winter photoperiods.
Seasonal changes in day length enhance or suppress aspects of immune function in mammals. Following adaptation to short, winter-like short photoperiods, cytokine and behavioral responses to lipopolysaccharide (LPS)-induced simulated infections are attenuated in LPS-naive Siberian hamsters. This experiment examined whether diminished initial responses to LPS in short days (SDs) are accompanied by decrements in the development of innate immunological memory that leads to endotoxin tolerance. ⋯ Thus despite engaging greater naive responses to LPS, LD hamsters exhibited incomplete LPS tolerance relative to SD hamsters. The expression of behavioral tolerance to endotoxin is relatively diminished during the breeding season, a time of year when naive responses to endotoxin are at their greatest. During winter, enhancements in behavioral endotoxin tolerance may conserve energy and facilitate survival in the face of energetically challenging conditions.
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Psychoneuroendocrinology · Jul 2007
Comparative StudyThe temporal dynamics of intrahippocampal corticosterone in response to stress-related stimuli with different emotional and physical load: an in vivo microdialysis study in C57BL/6 and DBA/2 inbred mice.
There is strong evidence for a pivotal interaction of corticosteroid signalling and behavioral adaptation to stress. To further elucidate this relation, we monitored the dynamics of free corticosterone in the murine hippocampus of two inbred mouse strains using in vivo microdialysis. C57BL/6JOlaHsd (C57BL/6) and DBA/2OlaHsd (DBA/2) inbred mouse strains have been shown to differ in their anxiety-related and depression-like behavior and provide, thus, an interesting animal model to study the stimulus-response profile of the hypothalamus-pituitary-adrenocortical (HPA) system as a function of emotional and physical load. ⋯ Though descriptive in nature, the present results suggest an altered corticosteroid signalling in the DBA/2 strain compared to C57BL/6 mice. Whether this observation causally underlies the differences in anxiety-related and depression-like behavior has to be further experimentally validated. In addition, our study highlights the use of in vivo microdialysis to assess the neuroendocrine endophenotype of animal models via profiling of stimulus-response patterns of stress hormones.
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The hypothesis that treatment with neuropeptide Y (NPY) can increase running activity and decrease food intake and body weight was tested. Female rats with a running wheel lost more weight than sedentary rats and ran progressively more as the availability of food was gradually reduced. When food was available for only 1h/day, the rats lost control over body weight. ⋯ By contrast, NPY stimulated food intake but not wheel running in rats which had food available continuously. These findings are inconsistent with the prevailing theory of the role of the hypothalamus in the regulation of body weight according to which food intake is a homeostatic process controlled by "orexigenic" and "anorexigenic" neural networks. However, the finding that treatment with NPY, generally considered an "orexigen", can increase physical activity and decrease food intake and cause a loss of body weight is in line with the clinical observation that patients with anorexia nervosa are physically hyperactive and eat only little food despite having depleted body fat and up-regulated hypothalamic "orexigenic" peptides.