Journal of neuroendocrinology
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J. Neuroendocrinol. · Aug 2004
Comparative StudyGlutamic acid decarboxylase 67 (GAD67) gene expression in discrete regions of the rostral preoptic area change during the oestrous cycle and with age.
Gamma-aminobutyric acid (GABA), an inhibitory neurotransmitter, is important to the timing and amplitude of the gonadotrophin-releasing hormone (GnRH)-induced luteinizing hormone (LH) surge on pro-oestrus. Data suggest that GABA input in the preoptic area must decrease for a normal LH surge to occur in young rats. We have previously found that ageing alters the timing and amplitude of the LH surge. ⋯ GAD(67) mRNA expression is high during the early morning hours of pro-oestrus and then declines around the time of the GnRH-induced LH surge. In addition, the diurnal rhythm disappears in the AVPV and is attenuated in the area surrounding the OVLT of middle-aged proestrous rats. These findings suggest that a loss of rhythmicity in GAD(67) gene expression and maintenance of inhibitory tone on proestrous afternoon may alter the timing and amplitude of the LH surge, as previously observed in middle-aged rats.
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J. Neuroendocrinol. · May 2004
Comparative StudyModulation of oestrogen receptor-beta mRNA expression in rat paraventricular and supraoptic nucleus neurones following adrenal steroid manipulation and hyperosmotic stimulation.
Magnocellular neurosecretory neurones in the hypothalamic paraventricular (PVN) and supraoptic (SON) nuclei express oestrogen receptor beta (ERbeta) but not ERalpha. In the PVN, ERbeta is strongly expressed in the ventromedial parvocellular neurones projecting to the brainstem. We used quantitative in situ hybridization, with (35)S-labelled riboprobes, to study heterologous regulation by manipulating adrenal steroid hormones (72 h after adrenalectomy +/- corticosterone replacement; repeated stress: halothane inhalation, environmental cold, immobilization, each daily for 3 days) in male rats. ⋯ However, ERbeta mRNA expression in magnocellular neurones is negatively linked to hyperosmotic stimulation of the neurones. The 6.25-fold variation in ERbeta mRNA expression in magnocellular neurones from salt-loading to adrenalectomy could alter their sensitivity to oestrogens. Consequently, regulation of oxytocin and vasopressin neurone activity via ERbeta is expected to vary according to their functional state and, in particular, on basal glucocorticoid actions.
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J. Neuroendocrinol. · May 2004
Acute intracarotid glucose injection towards the brain induces specific c-fos activation in hypothalamic nuclei: involvement of astrocytes in cerebral glucose-sensing in rats.
The detection of changes in glucose level constitutes the first step of the control of glucose homeostasis. Glucose sensors are therefore expected to be present in different parts of the body and particularly in the central nervous system. Some studies have already attempted to determine glucose-sensitive cerebral structures either after a glucoprivic stimulus or after prolonged hyperglycaemia. ⋯ After specific impairment of astrocyte metabolism by methionine sulfoximine, cerebral activation disappears in the arcuate nucleus, correlated with the lack of cerebral glucose-induced insulin secretion. Therefore, arcuate and paraventricular hypothalamic nuclei are able to detect acute cerebral hyperglycaemia, leading to a peripheral stimulation of insulin secretion. Arcuate nucleus and more especially astrocytes in this nucleus play a pivotal role in glucose-sensing.
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J. Neuroendocrinol. · Sep 2003
Palatable solutions during paradoxical sleep deprivation: reduction of hypothalamic-pituitary-adrenal axis activity and lack of effect on energy imbalance.
Paradoxical sleep deprivation (PSD) induces increased energy expenditure in rats, insofar as rats eat more but loose weight throughout the deprivation period. In the present study, rats were offered water, saccharin or sucrose to drink during the deprivation period, since it has been proposed that carbohydrates reduce the hypothalamic-pituitary-adrenal (HPA) axis response to stress. Rats were submitted to the flower pot technique for 96 h. ⋯ However, when given saccharin or sucrose, paradoxical sleep-deprived rats showed lower concentrations of ACTH and corticosterone than their water-provided counterparts, indicating that palatable fluids were capable of lowering HPA axis activation produced by PSD. The fact that PSD induced energy imbalance regardless of the relative attenuation of the HPA axis activity produced by saccharin or sucrose suggests that the HPA axis may play only a secondary role in this phenomenon, and that other mechanisms may account for this effect. The data also suggest that supply of palatable fluids can be an additional modification to reduce the stress of the flower pot method.
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J. Neuroendocrinol. · Feb 2003
Effect of intracerebroventricular administration of the octadecaneuropeptide on the expression of pro-opiomelanocortin, neuropeptide Y and corticotropin-releasing hormone mRNAs in rat hypothalamus.
Intracerebroventricular (i.c.v.) administration of the octadecaneuropeptide (diazepam-binding inhibitor [33-50]; ODN) exerts a potent anorexigenic effect in the rat. We studied the effect of ODN on three neuropeptides involved in feeding behaviour: the orexigenic peptide neuropeptide Y (NPY) and two anorexigenic peptides, corticotropin-releasing hormone (CRH) and the pro-opiomelanocortin (POMC)-derived peptide alpha-melanocyte-stimulating hormone. The effect of i.c.v. administration of ODN (0.1 microg/kg and 1 microg/kg) on mRNA expression of the peptides in male rat hypothalamus was evaluated by semiquantitative in situ hybridization. ⋯ Labelling obtained with the CRH cRNA probe was essentially distributed throughout the medial parvocellular area of the hypothalamic paraventricular nucleus. ODN, at doses of 0.1 and 1 microg/kg, resulted in 17.8% and 32.8% decreases in CRH mRNA expression, respectively. The present data suggest that ODN might exert its anorexigenic effect by increasing mRNA expression of POMC and decreasing mRNA expression of NPY in the arcuate nucleus.