Linked Life Data

2821424

Source:http://linkedlifedata.com/resource/pubmed/id/2821424

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
3
pubmed:dateCreated
1987-11-19
pubmed:abstractText
The effects of ovariectomy and of 17 beta-estradiol (estradiol) treatment in vivo and in vitro on the ability of melatonin to inhibit dopamine release from the female rat hypothalamus and on [125I]-iodomelatonin binding sites in the brains and hypothalami of female rats were investigated. In long-term (2-4 weeks) ovariectomized (OVX) female rats, the inhibitory effect of melatonin in vitro on dopamine release from the hypothalami was abolished. After implantation of estradiol capsules, the ability of melatonin to inhibit dopamine release from the hypothalamus was reinstated and resembled that observed in intact female rats at estrus and in females exhibiting spontaneous persisting estrus. Similar reinstatement of the responsiveness to melatonin was observed in hypothalami of OVX rats shortly (2 h) after a single subcutaneous injection of estradiol (200 micrograms/animal). Incubation of hypothalami of OVX rats in vitro for 50-90 min with estradiol (0.1-1 nM) resulted in a partial (up to 50%), time and steroid concentration-dependent reinstatement of the ability of melatonin to inhibit the induced dopamine release. Conversely, incubations with estradiol in vitro reduced the ability of melatonin to inhibit dopamine release from the hypothalami of intact rats at proestrus. Such incubations had no effect on the release of dopamine from hypothalami of rats at estrus or of short-term OVX (3 days) rats. The changes in the responsiveness of the hypothalamus to melatonin were accompanied by profound changes in the binding of [125I]-iodomelatonin, to synaptosomes isolated from whole brains and from hypothalami of the OVX female rats. In OVX rats, the densities of the binding sites in the brains and particularly in the hypothalami decreased to 18 and 24% respectively, of the values observed in control females at estrus. The apparent dissociation constant of the remaining sites was significantly lower (ca. 90 nM) than that observed in the intact controls (ca. 300 nM). An almost complete reinstatement of the [125I]-iodomelatonin binding sites was observed in synaptosomes prepared from the hypothalami of OVX rats shortly (2 h) after a single subcutaneous injection of estradiol, or after incubation with estradiol in vitro. The estradiol-mediated reinstatement of [125I]-iodomelatonin binding sites was less pronounced in synaptosomes prepared from whole brains. The results clearly show that estradiol directly modulates the responses of the dopaminergic neurosecretory system in the hypothalamus to melatonin. This phenomenon may be primarily associated with the estradiol-induced changes in the density and function of melatonin receptors in the hypothalamus.(ABSTRACT TRUNCATED AT 400 WORDS)
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Sep
pubmed:issn
0028-3835
pubmed:author
pubmed:issnType
Print
pubmed:volume
46
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
207-16
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
1987
pubmed:articleTitle
Regulation of melatonin's activity in the female rat brain by estradiol: effects on neurotransmitter release and on iodomelatonin binding sites.
pubmed:affiliation
Department of Biochemistry, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Israel.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't