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  • 1
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The effects of chronic immune challenge on cytokine expression and hypothalamic-pituitary-adrenal axis (HPA) axis responses to stress were studied in Wistar rats after administration of increasing doses of lipopolysaccharide (LPS). Repeated LPS (R-LPS) decreased body weight and increased adrenal weight and pituitary pro-opiomelanocortin mRNA levels. LPS injection increased plasma adrenocorticotropic hormone (ACTH) and corticosterone but the effect was attenuated in R-LPS. Plasma corticosterone but not ACTH responses to restraint were also reduced in R-LPS. Basal and restraint-stimulated corticotropin releasing hormone (CRH) mRNA levels were lower in R-LPS, but responses to a new LPS injection were similar to controls. In contrast, type 1 CRH receptor (CRH-R1) mRNA responses to both LPS and restraint were blunted in R-LPS. Vasopressin mRNA levels in parvocellular neurones were higher in R-LPS, and increased further after restraint but not after a new LPS injection. Glucocorticoid receptor (GR) levels in the paraventricular nucleus (PVN) increased after a single LPS or R-LPS (24 h after the last injection) but declined after a new injection in R-LPS. Interleukin (IL)-1β and IL-6 mRNAs increased in the pituitary, spleen and circumventricular organs after single or R-LPS, suggesting that cytokines may contribute to the activation of the HPA axis though pathways from the circumventricular organs as well as paracrine effects in the pituitary. The data show that (i) adaptation of the HPA axis during repeated LPS injection involves increases in vasopressin : CRH expression ratios in parvocellular neurones; (ii) that hypothalamic CRH and vasopressin responses to acute stimulation are independent of CRH-R1 expression in the PVN; and (iii) there is a dissociation between pituitary and adrenal responses to acute stress suggesting a decrease of adrenal sensitivity to ACTH.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Journal of neuroendocrinology 16 (2004), S. 0 
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The aim of this study was to test whether environmental enrichment alters the status and responsiveness of pituitary-adrenocortical and sympathetic-adrenomedullary hormones in rats. Previous studies have shown that rats kept in an enriched environment differ from those kept in standard cages in dendritic branching, synaptogenesis, memory function, emotionality and behaviour. In male Wistar rats kept in an enriched environment for 40 days, we studied basal concentrations of hormones, endocrine responses to 5-HT1A challenge and responsiveness and adaptation to repeated handling. Environmental enrichment consisted of large plexiglass cages with 10 rats per cage, which contained variety of objects exchanged three times a week. Rats kept in this enriched environment had higher resting plasma concentrations of corticosterone, larger adrenals and increased corticosterone release to buspirone challenge compared to controls. Lower adrenocorticotropic hormone, corticosterone and adrenaline responses to handling were noticed in rats kept in an enriched environment. Exposure to repeated handling led to a more rapid extinction of corticosterone responses in rats kept in an enriched environment. Thus, environmental enrichment leads to pronounced changes in neuroendocrine regulation, including larger adrenals and increased adrenocortical function, which are so far considered to be indication of chronic stress.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Psychopharmacology 85 (1985), S. 201-203 
    ISSN: 1432-2072
    Keywords: ACTH ; Corticosterone ; Dopamine receptors ; Apomorphine ; Haloperidol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of a dopaminergic agonist, apomorphine, and a dopaminergic antagonist, haloperidol, on plasma ACTH, and corticosterone levels were evaluated in adult male rats. Subcutaneous administration of apomorphine in the dose range of 50–500 μg · kg−1 significantly increased plasma corticosterone levels. Acute treatment with apomorphine (250 μg · kg−1) resulted in an elevation of plasma ACTH concentration, peak values being reached 15 min after the injection. The apomorphine-induced rise in plasma ACTH levels was completely inhibited by pretreatment with haloperidol (1 mg · kg−1). A stimulatory role for dopamine receptors in the control of pituitary ACTH release in the rat is suggested.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-0533
    Keywords: Horseradish peroxidase ; Adrenocorticotropic hormone and corticosterone release ; Stress ; Blood-brain barrier ; Vascular permeability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Wistar rats were given intravenous (i.v.) horseradish peroxidase (HRP) in saline in doses commonly used to study vascular permeability and the blood-brain barrier. Samples of blood were taken from conscious animals via indwelling catheters at intervals up to 6 h after the HRP injection. Plasma concentrations of adrenocorticotropic hormone (ACTH) and corticosterone were determined and compared with levels in control rats injected with saline alone. Rats injected with saline only presented levels of hormones within the low limits of normal indicating an insignificant influence of stress induced by the experimental procedure. Within 30 min of the i.v. HRP injection, the plasma concentrations of both ACTH and corticosterone increased to very high levels and remained so throughout the period of observation, namely 6 h. The time course of the changes in the concentrations was the same for the two hormones and the actual numerical values were related to the dose of HRP injected. The i. v. injection of HRP in Wistar rats, therefore, induces a marked release of stress hormones which by themselves have profound physiological effects. This phenomenon must be taken into account, in studies on normal vascular permeability using HRP as a tracer and also in similar experiments exploring various pathological conditions of the blood-brain barrier.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1439-6327
    Keywords: Exercise ; Testostereone ; Adrenaline ; Noradrenaline
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Plasma testosterone, noradrenaline, and adrenaline concentrations during three bicycle ergometer tests of the same total work output (2160 J·kg−1) but different intensity and duration were measured in healthy male subjects. Tests A and B consisted of three consecutive exercise bouts, lasting 6 min each, of either increasing (1.5, 2.0, 2.5 W·kg−1) or constant (2.0, 2.0, 2.0 W·kg−1) work loads, respectively. In test C the subjects performed two exercise bouts each lasting 4.5 min, with work loads of 4.0 W·kg−1. All the exercise bouts were separated by 1-min periods of rest. Exercise B of constant low intensity resulted only in a small increase in plasma noradrenaline concentration. Exercise A of graded intensity caused an increase in both catecholamine levels, whereas, during the most intensive exercise C, significant elevations in plasma noradrenaline, adrenaline and testosterone concentrations occurred. A significant positive correlation was obtained between the mean value of plasma testosterone and that of adrenaline as well as noradrenaline during exercise. It is concluded that both plasma testosterone and catecholamine responses to physical effort depend more on work intensity than on work duration or total work output.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-6830
    Keywords: plasma catecholamines ; norepinephrine ; epinephrine ; anterolateral hypothalamic deafferentation ; effect of vasopressin and 1-deamino-8-d-arginine-vasopressin (DDAVP) ; immobilization stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary 1. Anterolateral cut (ALC) of the medial basal hypothalamus (MBH) in rats produces an elevation of plasma catecholamine levels, especially of norepinephrine (NE), in unstressed animals and a more pronounced rise of plasma NE levels in response to immobilization (IMO). Animals with ALC have a destroyed corresponding vasopressin (AVP) and other peptides containing innervation of the median eminence and the posterior pituitary, resulting in the prevention of increased AVP secretion during the early intervals of IMO. 2. The administration of AVP (Pitressin, 7 days, 1 IU per rat i.m.) or of 1-deamino-8-d-arginine-vasopressin (DDAVP), an AVP analogue without pressoric activity, taken in drinking water (about 100µg per day) was almost equally potent in decreasing the elevated water consumption and plasma NE levels in unstressed rats with ALC. However, the stress-induced potentiation of plasma NE levels in rats with ALC was not influenced by AVP substitution and only partly reduced by DDAVP in the late IMO intervals. 3. The lack of circulating vasopressin is the main factor in the mechanism of increased activity of the sympathoadrenal system induced by ALC in unstressed rats. 4. The regulation of sympathoadrenal activity by vasopressin and DDAVP in rats with ALC seems to be mediated predominantly by V2-subtype receptors. 5. In stressed rats with ALC the potentiation of plasma NE levels was not reduced after AVP or DDAVP administration, suggesting that some addition regulatory mechanisms were involved.
    Type of Medium: Electronic Resource
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  • 8
    Publication Date: 2015-09-15
    Description: Variation in predator behavior toward aposematic prey was frequently studied at interspecific and individual levels, but interpopulation differences have been neglected. Geographic differences in prey fauna offer an opportunity to test their implications for predator behavior. It can be expected that 1) predator populations inhabiting environments with high diversity of aposematic prey are more neophobic than those living in areas where aposematic prey are scarce, and 2) different levels of neophobia jointly with avoidance learning affect selection on aposematic prey. We compared the behavior of wild-caught great tits ( Parus major ) from Bohemia and Central Finland toward aposematic firebugs ( Pyrrhocoris apterus ), nonaposematic firebugs, novel objects and novel palatable nonaposematic prey. Finnish and Bohemian birds did not differ in their novel-object exploration, but Finnish birds hesitated longer than Bohemian birds before resuming feeding next to a novel object. Latencies to attack novel palatable prey did not differ and were not correlated with the attitude toward novel objects. Tits from the Bohemian population mostly avoided aposematic firebugs and attacked nonaposematic ones. Finnish birds were more likely to attack both firebug color forms, and their attack latencies were correlated with latencies of attacking novel palatable prey. Thus, Bohemian birds avoided the aposematic prey, but were not more neophobic than Finnish birds. These results suggest that differences between Finnish and Bohemian birds in behavior to aposematic prey do not follow differences in exploration strategy and neophobia. The observed differences can be explained by a different experience with local aposematic prey communities.
    Print ISSN: 1045-2249
    Electronic ISSN: 1465-7279
    Topics: Biology
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