Linked Life Data

9832448

Source:http://linkedlifedata.com/resource/pubmed/id/9832448

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
12
pubmed:dateCreated
1998-12-24
pubmed:abstractText
In ewes, photoperiod modulates LH release. The median eminence (ME) dopaminergic activity seems to be implicated in the inhibition of LH secretion by photoperiod. This study investigated the functional importance of ME dopaminergic activity for LH secretion inhibition in three inhibitory photoperiodic treatments: after 33 long days (LD) (LD1 treatment), after 72 LD (LD2 treatment), and after 34 short days. Using reverse microdialysis on three groups of seven ewes, a solution of alpha-methyl-paratyrosine [alphaMPT, an inhibitor of tyrosine hydroxylase (TH); 10 mM in Ringer's lactate] was infused into the ME for 5 h, preceded by a 5-h control period during which only vehicle was infused, in each of the three photoperiodic treatments. AlphaMPT dramatically decreased the 3,4-dihydroxyphenylacetic acid concentration, similarly in all three photoperiodic treatments, suggesting a similar inhibition of TH activity. In the LD1 treatment, alphaMPT significantly increased LH pulse frequency (+1.22 +/- 0.46 pulse/5 h from control period, mean +/- SEM, n = 9; P < 0.05) and mean concentration (+51 +/- 28%; P < 0.001). In the other two photoperiodic treatments, alphaMPT had no significant effect on LH release. Thus, blockade of dopamine synthesis in the ME seems to stimulate LH secretion in early, but not long-term, inhibition by LD nor after the transition to short days. Therefore, dopaminergic activity of the ME seems to be critical for LH secretion inhibition in some photoperiodic inhibitory treatments but not in others.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
AIM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Dec
pubmed:issn
0013-7227
pubmed:author
pubmed:issnType
Print
pubmed:volume
139
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
5094-102
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
1998
pubmed:articleTitle
Median eminence dopaminergic activation is critical for the early long-day inhibition of luteinizing hormone secretion in the ewe.
pubmed:affiliation
Institut National de la Recherche Agronomique, Unité de Recherche Associeé Centre National de la Recherche Scientifique 1291, Laboratoire de Neuroendocrinologie Sexuelle, Nouzilly, France.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't