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Estrogen induces a rapid increase in galanin levels in female rat hippocampal formation: possibly a nongenomic/indirect effect
Linköping University, Department of Clinical and Experimental Medicine, Clinical Chemistry. Linköping University, Faculty of Health Sciences.
Linköping University, Department of Clinical and Experimental Medicine, Clinical Chemistry. Linköping University, Faculty of Health Sciences.
Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden .
Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden .
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2005 (English)In: European Journal of Neuroscience, ISSN 0953-816X, E-ISSN 1460-9568, Vol. 21, no 8, 2089-2099 p.Article in journal (Refereed) Published
Abstract [en]

Administration of 17β-estradiol to ovariectomized rats increased the concentrations of galanin-like immunoreactivity (LI) in the hippocampal formation by 215% (P < 0.001) within 1 h. An increase of 125% (P < 0.05) was observed in the same brain region in the proestrous phase of a normal estrous cycle. Tamoxifen® did not block the 17β-estradiol-induced increase in the concentration of galanin-LI but resulted in a 62% decrease in the hypothalamus within 1 h. In vivo microdialysis in the dorsal hippocampal formation showed a decrease of extracellular galanin-LI (P < 0.001) 1−2 h after treatment with 17β-estradiol, indicating a decreased release of galanin. For comparision, we studied the concentrations of neuropeptide Y, which were not influenced significantly in any of the regions studied. Taken together our results suggest that 17β-estradiol inhibits galanin release, presumably from noradrenergic nerve terminals, and primarily via a nongenomic/indirect action, not necessarily involving the classical nuclear receptors ER-α or ER-β. These rapid estrogen-induced changes in galanin release could influence transmitter signalling and plasticity in the hippocampal formation.

Place, publisher, year, edition, pages
2005. Vol. 21, no 8, 2089-2099 p.
Keyword [en]
estrogen receptors, immunohistochemistry, in situ hybridization, microdialysis, radioimmunoassay
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-13379DOI: 10.1111/j.1460-9568.2005.04050.xOAI: oai:DiVA.org:liu-13379DiVA: diva2:20542
Available from: 2005-09-29 Created: 2005-09-29 Last updated: 2017-12-13
In thesis
1. Galanin and NPY in the rodent brain: rapid effects of 17beta-estradiol and possible roles in hippocampal plasticity
Open this publication in new window or tab >>Galanin and NPY in the rodent brain: rapid effects of 17beta-estradiol and possible roles in hippocampal plasticity
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The neuropeptides galanin and neuropeptide Y (NPY) play an important role in the reproduction of rodents, e.g. by modulating the release of gonadal hormones, the nutritional status by effects on feeding behavior and also by influencing mating behavior. There are age- and gender- differences in galanin- and NPY- like immunoreactivities (LIs) in brain areas important for higher functions including the hippocampal formation (HiFo) and cortex, that are related to the concentrations of 17β-estradiol.

Neuropeptides in general are currently not considered critical in normal integrative neuronal functions but are rather thought to act as slow modulators during periods of stress or injury. In the present thesis we attempted to investigate, if the normal cyclical changes in the female sex-hormone 17β-estradiol can affect neurotransmission in brain areas important for memory, cognition and mood. We studied not only ”long term” (days and weeks) but also ”short-term” (one hour) effects on galanin and NPY concentrations in 17β-estradiol-primed ovariectomized (ovx) rats and mice.

Radioimmunoassay (RIA) of galanin-LI in extracts of brain tissues from ”long-term” 17β-estradiol-treated ovx rats showed that its effects on galanin are dependent on boththe dose and on duration. Galanin - and NPY-LI in brain tissues of young ovx rats and mice increased in response to 17β-estradiol treatment in the HiFo, frontal cortex and striatum already within hours. This effect was not blocked by Tamoxifen® in rats. The mechanism of the 17β-estradiol effects on galanin levels in the rat HiFo may be related to decreased release of galanin into the extracellular fluid, since galanin-LI decreased in microdialysis samples two hours after a single injection of 17β-estradiol. Species differences were observed with regards to galanin, possibly due to tissue and species differences in the distribution of estrogen receptors.

In the HiFo and caudate nucleus of mice, we found an increase in NPY-transcript after two hours by means of insitu hybridization, perhaps a compensatory up-regulation of NPY mRNA after increased 17β-estradiol-induced release in these areas. Taken together with no effects of Tamoxifen® on the levels on galanin in the HiFo of rats, the short duration, and the fact that the density of classical estrogen receptors seems to be limited in the striatum, we suggest that these effects are mediated through a membrane-related mechanism perhaps not involving the classical ER route.

With an antiserum raised against the C-terminal end of the first 16 aminoacids of galanin- the sequence important for binding of intact galanin to its receptor - we found a novel compound which appears to be a homologue to galanin. Chromatographical analysis revealed that it was not galanin(1-29) or the galanin related peptide, galaninlike peptide (GALP), but appeared with immunohistochemistry in the galanin systems in the brain and was further influenced by 17β-estradiol in the HiFo and frontal cortex in a similar manner as galanin(1-29).

In conclusion, tissue concentrations of galanin, a putative galanin homologue and NPY can be altered already after one hour by 17β-estradiol treatment e.i. in the HiFo. These ”short-term” effects are most likely to be due to effects on estrogen-primed peptide release which might influence mechanisms important for memory, cognition and mood.

Place, publisher, year, edition, pages
Institutionen för biomedicin och kirurgi, 2005
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 911
Keyword
Sex-hormones, Brain, Neuropeptides
National Category
Neurosciences
Identifiers
urn:nbn:se:liu:diva-4152 (URN)91-85299-24-3 (ISBN)
Public defence
2005-09-07, Berzeliussalen, Campus US, Ingång 65, Linköpings universitetssjukhus, Linköping, 09:00 (English)
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Available from: 2005-09-29 Created: 2005-09-29 Last updated: 2009-08-23

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Hilke, SusanneTheodorsson, AnetteHolm, LovisaTheodorsson, Elvar

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