Linked Life Data

11244296

Source:http://linkedlifedata.com/resource/pubmed/id/11244296

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PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
2
pubmed:dateCreated
2001-3-13
pubmed:abstractText
In this study we examined the release of dopamine and noradrenaline in the ventromedial hypothalamus (VMH) of ovariectomized ewes during the oestrogen-induced luteinizing hormone (LH) surge by measuring their respective metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and methoxyhydroxyphenylglycol (MHPG) using microdialysis. Further we investigated whether inhibition of catecholamine synthesis in the VMH by bilateral reverse dialysis of alpha-methyl-p-tyrosine (alpha-MPT) would block the oestrogen-induced LH and/or prolactin surges. Oestradiol treatment (50 microg oestradiol benzoate) of ovariectomized ewes resulted in a biphasic LH response, significantly (p < 0.05) decreasing LH concentrations from 2.5 to 10.5 h after injection, followed by an LH surge beginning at 16 h. Prolactin concentrations were also significantly (p < 0.05) increased in oestradiol-treated ewes from 13 h. VMH DOPAC concentrations in oil-vehicle-treated animals were at the level of detection (0.02 ng/ml) in most samples over the 24-hour sampling period. In oestradiol-treated ewes, VMH DOPAC levels were initially low before and up to 8 h after oestradiol injection but then increased significantly (p < 0.05) at 10-12 h and remained elevated up to 20 h after injection. In contrast, oestradiol injection had no effect on MHPG concentrations in the VMH. Bilateral reverse microdialysis of alpha-MPT into the VMH significantly (p < 0.05) delayed the time from oestradiol injection to the onset of the LH surge, the time to peak LH concentration and attenuated the LH surge compared with reverse dialysis of Ringer solution alone. In contrast, alpha-MPT treatment had no effect upon the oestradiol-induced increase in prolactin concentrations. This study provides evidence that the VMH is an important hypothalamic site in the neuro-endocrine control of the LH surge in ewes. The results suggest that dopaminergic neurons with terminals in the VMH are part of a neuronal pathway mediating the positive feedback effects of oestradiol on gonadotropin-releasing hormone secretion and the LH surge.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Feb
pubmed:issn
0028-3835
pubmed:author
pubmed:copyrightInfo
Copyright 2001 S. Karger AG, Basel.
pubmed:issnType
Print
pubmed:volume
73
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
91-101
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
2001
pubmed:articleTitle
Dopaminergic input to the ventromedial hypothalamus facilitates the oestrogen-induced luteinizing hormone surge in ewes.
pubmed:affiliation
Department of Physiology and Pharmacology, University of Queensland, St. Lucia, Queensland, Australia. anderson@plpk.uq.edu.au
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't