| Project/Area Number |
07807150
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Obstetrics and gynecology
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| Research Institution | HIROSAKI UNIVERSITY |
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Principal Investigator |
KAGIYA Akifumi HIROSAKI UNIVERSITY HOSPITAL,ASSISTANT PROFESSOR, 医学部・付属病院, 助教授 (70111226)
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| Co-Investigator(Kenkyū-buntansha) |
SAITO Yoshiharu HIROSAKI UNIVERSITY SCHOOL OF MEDICINE,PROFESSOR, 医学部, 教授 (00006769)
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| Project Period (FY) |
1995 – 1996
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| Project Status |
Completed (Fiscal Year 1996)
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| Budget Amount *help |
¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 1996: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1995: ¥600,000 (Direct Cost: ¥600,000)
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| Keywords | LH-RH neuron / Synapse / Estrogen / Preoptic area / Arcuate nucleus / Menopause |
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| Research Abstract |
The synaptic plasticity of hypothalamic and preoptic LH-RH neurons of female rats was studied immunohistochemically by the electron microscopic technique. In this investigation, we used young female adult rats which had regular cycles, received ovariectomy and estrogen valerate injection.
LH-RH immunoreactive cells were relatively large and bipolar shaped and observed in the preoptic and hypothalamic arcuate nucleus of rats, in these area LH-RH neurons were connected directly or indirectly to dopaminergic and GABA-ergic neurons each other. The hypothalamic arcuate nucleus is rich in estrogen receptors and is involved in the regulation of gonadotrophin and other hypophysiotropic hormone secretion. The ovarian cycle of rat was accompanied by changes in numbers of axosomatic synapses in the hypothalamic arcuate nucleus. In our observation, the number of axosomatic synapses in arcuate nucleus and preoptic area was increased at proestrus and decreased thereafter to estrus. At estrus synaptic number was most decreased than other sexual stages (metestrus and diestrus). In ovariectomized rats, axosomatic synaptic number in arcuate nucleus was decreased moreover, etradiol injection to cycling adult female rats resulted in a loss of axosomatic synapses in a degree of 28.8% decrease that was observed 3 weeks after injection.
These results mean changes in synaptic relationships occur on a day-to-day basis over the course of the estrus cycle, potentially as a result of fluctuating levels of gonadal steroids. Finding estrogen-induced synaptic plasticity in neural circuitry that controls gonadotrophins has raised the possibility that this plasticity may be one of the mechanisms by which estrogen regulates gonadotrophins at the central level. But as for synaptic actions of estrogen we need further researches including that of the glial reactivity to synaptic changes and of morphological changes by many neurochemical factors in several regions of the hypothalamus of female rats.
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