Noradrenergic control of GnRH release from the ewe hypothalamus in vitro: sensitivity to oestradiol.
Reprod Domest Anim
; 43(6): 753-9, 2008 Dec.
Article
em En
| MEDLINE
| ID: mdl-18484954
ABSTRACT
The present study investigates the influence of alpha(1)-adrenoreceptors in GnRH release in vitro and determines whether oestradiol modulates alpha(1)-adrenoreceptor-GnRH interaction. Within 10 min after ewe sacrifice, saggital midline hypothalamic slices were dissected, placed in oxygenated Minimum Essential Media-alpha (MEM-alpha) at 4 degrees C and within 2 h were singly perifused at 37 degrees C with oxygenated MEM-alpha (pH 7.4; flow rate 0.15 ml/min), either with or without oestradiol (24 pg/ml). After 4-h equilibration, 10-min fractions were collected for 4 h interposed with a 10-min exposure at 60 min to specific alpha(1)-adrenoreceptor agonist (methoxamine) or antagonist (thymoxamine) at various doses (0.1-10 mm). The alpha(1)-adrenoreceptor agonist (10 mm) increased (p < 0.05) GnRH release at 90 min both in presence and absence of oestradiol. However, in presence of oestradiol, alpha(1)-adrenoreceptor agonist (10 mm)-induced GnRH release remained elevated (p < 0.05) for at least 60 min. The bioactivity of the released GnRH was studied using a hypothalamus-pituitary sequential double-chamber perifusion. Only after exposure of hypothalamic slices to alpha(1)-adrenoreceptor agonist (10 mm), did the hypothalamic eluate stimulate LH release from pituitary fragments (n = 9, 7.8 +/- 12.3-36.2 +/- 21.6 ng/ml) confirming that the alpha(1)-adrenoreceptor agonist stimulated release of biologically active GnRH. In summary, GnRH release from the hypothalamus is under stimulatory noradrenergic control and this is potentiated in the presence of oestradiol.
Texto completo:
1
Base de dados:
MEDLINE
Medicinas Complementares:
Homeopatia
Assunto principal:
Ovinos
/
Hormônio Liberador de Gonadotropina
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Receptores Adrenérgicos alfa 1
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Estradiol
/
Hipotálamo
Tipo de estudo:
Diagnostic_studies
Idioma:
En
Revista:
Reprod Domest Anim
Ano de publicação:
2008
Tipo de documento:
Article
País de afiliação:
Reino Unido