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The effect of corticotropin releasing factor (CRF) on the gonadotropin hormone releasing hormone (GnRH) hypothalamic neuronal system during preovulatory period in the ewe

100%
Polkowska J., Przekop F.
Acta Neurobiologiae Experimentalis
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1997
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vol. 57
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issue 2
91-99
EN
Effects of infusions of corticotropin releasing factor (CRF) into the 3rd ventricle of the brain of ewes during the proestrus on the immunoreactive (ir) gonadotropin hormone releasing hormone (GnRH) neuronal system, pituitary luteinizing hormone(LH) producing cells and LH concentrations in the blood plasma were studied. None of the CRF treated sheep displayed the estrous activity nor ovulated on the day of estrus (17th day of the cycle), and two days later when they were slaughtered. The GnRH center of CRF treated ewes situated in the preoptico septal area was well organized , but irGnRH stores in the median eminence were low in comparison to the controls (sheep from the late follicular phase of the estrous cycle). The feature and the number of LH cells in CRF treated ewes were typical for the preovulatory phase of the cycle but the plasma concentrations of LH did not exceed basal levels. These results suggest that CRF induced decrease of irGnRH stores in the nerve terminals of the ME can be responsible for the blockade of the preovulatory surge of GnRH/LH in the sheep.
2
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Responses in the hypothalmic monoaminergic system activity in ewes to beta-endorphin, CRF and their antagonists

100%
Przekop F., Tomaszewska D.
Acta Neurobiologiae Experimentalis
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1996
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vol. 56
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issue 3
807-817
EN
This article reviews data concerning the action of opioidergic and monoaminergic system on LHRH secretion.Generally, in anestrus ewes beta-endorphin and/or corticoloberin significantly change extracellular concentrations of monoamine metabolites in the MBH-ME, but in estrus ewes both beta-endorphin and CRF alters also dopamine, noradrenaline and serotonin levels.Responses of catecholaminergic and serotoninergics system in the MBH-ME to naloxone or CRF-antagonist depend, to a large degree, on the phase of reproduction.In anestrous ewes subjected to stressful stimuli an opiate receptor blocker, naloxone, and CRF-antagonist attenuate the stress - induced activity of catecholaminergic and serotoninergic system in the MBH-ME; in non-stressed animals they suppress only serotoninergic system activity in this structure.No clear explanation can be offered now for either differences in response of catecholaminergic and serotoninergic system in MBH to beta-endorphin and CRF in various periods of reproduction or for differences in the response of these systems to CRF antagonist and naloxone in non-stressed and stressed ewes.It has been suggested that the responses in monoaminergic system activity are highly dependent upon the physiological state of the animal and that beta-endorphin and corticoliberin may indirectly modulate LHRH and other hypothalmic hormone secretion by monoaminergic systems.
3
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Effect of stress on the expression of GnRH and GnRH receptor (GnRH-R) genes in the preoptic area-hypothalamus and GnRH-R gene in the stalk/median eminence and anterior pituitary gland in ewes during follicular phase of the estrous cycle

61%
Ciechanowska M., Lapot M., Malewski T., Misztal T., Mateusiak K., Przekop F.
Acta Neurobiologiae Experimentalis
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2007
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vol. 67
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issue 1
1-12
EN
The RT-PCR (reverse transcription polymerase chain reaction) technique was used to analyze GnRH mRNA and GnRH-R mRNA in the preoptic area, anterior and ventromedial hypothalamus, and GnRH-R mRNA in the stalk/median eminence and anterior pituitary gland of follicular ewes subjected to short (3 h during one day) or prolonged (5 h daily during four consecutive days) footshock stimulation. To analyze relationship between expression of GnRH and GnRH-R genes with LH secretion the blood samples were collected at 10 min intervals to determine LH levels in control and stressed animals. The concentration of GnRH mRNA increased significantly in the preoptic area, anterior and ventromedial hypothalamus of ewes subjected to short stress. The prolonged stressful stimuli significantly decreased GnRH mRNA levels in all analyzed structures. In short stressed ewes the significant augmentation of mRNA encoding GnRH-R was detected in the preoptic area, entire hypothalamus, stalk/median eminence and anterior pituitary gland. The GnRH-R mRNA was significantly reduced in all tested structures of animals subjected to prolonged footshocking except for the preoptic area, where GnRH-R mRNA did not differ from control values. The changes in GnRH mRNA and GnRH-R mRNA levels under short or prolonged stress were associated with an increase or decrease of LH concentration in blood plasma, suggesting the existence of a direct relationship between GnRH mRNA and GnRH-R mRNA expression with LH secretion. The results indicate that the expression of both GnRH gene and GnRH-R gene, as well as LH secretion in ewes during the follicular phase of the estrous cycle, are dependent upon the kind of stress.
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