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  • 1
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: In humans, an altered control of cortisol secretion was reported in adult men born with a low birth weight making the hypothalamic-pituitary-adrenal (HPA) axis a possible primary target of early life programming. In rats, we have recently shown that maternal food restriction during late pregnancy induces both an intrauterine growth retardation and an overexposure of fetuses to maternal corticosterone, which disturb the development of the HPA axis in offspring. The first aim of this work was to investigate, in adult male rats, whether perinatal malnutrition has long-lasting effects on the HPA axis activity during both basal and stressful conditions. Moreover, as the HPA axis and sympathetic nervous system are both activated by stress, the second aim of this work was to investigate, in these rats, the adrenomedullary catecholaminergic system under basal and stressful conditions. This study was conducted on 4-month-old male rats malnourished during their perinatal life and on age-matched control animals. Under basal conditions, perinatal malnutrition reduced body weight and plasma corticosteroid-binding globulin (CBG) level but increased mineralocorticoid receptor (MR) gene expression in CA1 hippocampal area. After 30 min of restraint, perinatally malnourished (PM) rats showed increased plasma noradrenaline, adrenocorticotropin hormone (ACTH) and corticosterone concentrations similarly as controls, but calculated plasma-free corticosterone concentration was significantly higher and adrenaline level lower than controls. During the phase of recovery, PM rats showed a rapid return of plasma ACTH and corticosterone concentrations to baseline levels in comparison with controls. These data suggest that in PM rats, an elevation of basal concentrations of corticosterone, in face of reduced CBG and probably increased hippocampal MR lead to a much larger impact of corticosterone on target cells that mediate the negative-feedback mechanism on the activities of both the HPA axis and sympathoadrenal one.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Journal of neuroendocrinology 17 (2005), S. 0 
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Oestrogen powerfully affects the secretion of gonadotropin-releasing hormone (GnRH) from the brain in all species investigated, including sheep. Until recently, it was hypothesised that such regulation occurs indirectly because few or no GnRH neurones were found to express oestrogen receptor (ER) α. The discovery of a second oestrogen receptor, ERβ, and its subsequent localisation in numerous GnRH neurones in the rat, led to a reconsideration of this hypothesis. However, colocalisation of immunoreactive ERβ protein in GnRH neurones has only been demonstrated in the rat, raising the possibility that such putative direct regulation of GnRH neurones by oestrogen may be peculiar to this species. We have previously shown that steroid receptors in the sheep brain are acutely sensitive to fixation and the full complement of immunoreactive cells can only be visualised after antigen retrieval. The aims of this study were therefore to map immunocytochemically the distribution of ERβ neurones in the ewe brain, and to determine which proportion of GnRH neurones express ERβ. Brain sections (20 µm) from four ewes killed in anestrus were subjected to high temperature antigen retrieval and immunocytochemistry. Numerous ERβ-immunoreactive cells were located throughout the hypothalamus and, following dual-label immunocytochemistry, over 50% of the GnRH neurones were found to express immunoreactive ERβ. The functional significance of these ERβ-expressing GnRH neurones in the ovine brain remains to be determined.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science, Ltd
    Journal of neuroendocrinology 15 (2003), S. 0 
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The neuropeptide, galanin, has been implicated to play a significant role in numerous physiological functions, including reproduction. Studies on several species have shown that galanin enhances gonadotropin-releasing hormone (GnRH)-induced luteinizing hormone secretion. In rodents, a subset of GnRH neurones expresses galanin in a sexually dimorphic manner and it has been suggested that this may underpin the differences in GnRH secretion observed between the sexes. However, there are few data available for other species. Previous studies in sheep have shown that the distribution of GnRH neurones overlaps with galanin cells. The primary objectives of our study were to determine whether GnRH and galanin coexist in the sheep brain and, importantly, if a sex difference is apparent in the colocalization of these two peptides. Using immunocytochemistry coupled to high temperature antigen retrieval, we found that all GnRH neurones in the ovine brain colocalize with galanin. There is also a distinct population of galanin neurones that do not secrete GnRH. In addition, the distribution of galanin-immunoreactive cells was similar to that previously reported for colchicine treated ewes and, in agreement with earlier studies, the number of GnRH neurones did not differ between rams and ewes or between ewes killed at different stages of the oestrous cycle. These results suggest that, in sheep, GnRH and galanin may be cosecreted but the functional significance of this coexpression and possible cosecretion remains to be elucidated.
    Type of Medium: Electronic Resource
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