umu.sePublications
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
GABA(A) receptor changes in acute allopregnanolone tolerance
Umeå University, Faculty of Medicine, Department of Clinical Sciences, Obstetrics and Gynaecology.
Umeå University, Faculty of Medicine, Department of Clinical Sciences, Obstetrics and Gynaecology.
Umeå University, Faculty of Medicine, Department of Clinical Sciences, Obstetrics and Gynaecology.
Umeå University, Faculty of Medicine, Department of Clinical Sciences, Obstetrics and Gynaecology.
Show others and affiliations
2006 (English)In: European Journal of Pharmacology, ISSN 0014-2999, E-ISSN 1879-0712, Vol. 535, no 1-3, 125-134 p.Article in journal (Refereed) Published
Abstract [en]

To study acute tolerance, rats were anesthetized with interrupted i.v. allopregnanolone infusions where the "silent second" in the electroencephalogram (EEG) was the target. Animals were killed either directly at the first silent second or at the silent second level after 30 or 90 min of anaesthesia. Acute tolerance was demonstrated at 90 min of anaesthesia as earlier shown. In situ hybridization showed a decreased expression of the gamma-aminobutyric acid(A) (GABA(A)) receptor subunit alpha4mRNA amount in the thalamus ventral-posteriomedial nucleus of the tolerant rats. A parallel change in the abundance of the alpha4 subunit was detected with immunohistochemistry. The increase in maintenance dose rate (MDR) was significantly negatively correlated with the alpha4mRNA in the thalamus ventral-posteriomedial nucleus, and positively correlated with alpha2mRNA in different hippocampal subregions. There was also a positive relationship between the alpha1mRNA amounts in the different hippocampal subregions, with significant differences between groups. These changes in GABA(A) receptor subunits mRNA expression and protein (alpha4) might be of importance for the development of acute tolerance to allopregnanolone.

Place, publisher, year, edition, pages
2006. Vol. 535, no 1-3, 125-134 p.
Keyword [en]
Anesthetics/administration & dosage/blood/pharmacokinetics, Animals, Brain/*drug effects/metabolism, Brain Chemistry/drug effects, Dentate Gyrus/chemistry/drug effects/metabolism, Dose-Response Relationship; Drug, Drug Tolerance, Gene Expression/drug effects, Immunohistochemistry, In Situ Hybridization, Infusions; Intravenous, Male, Pregnanolone/*administration & dosage/blood/pharmacokinetics, Protein Subunits/analysis/genetics, RNA; Messenger/genetics/metabolism, Rats, Rats; Sprague-Dawley, Receptors; GABA-A/analysis/*genetics, Receptors; GABA-B/analysis/genetics, Ventral Thalamic Nuclei/chemistry/drug effects/metabolism
Identifiers
URN: urn:nbn:se:umu:diva-16927DOI: 10.1016/j.ejphar.2006.01.059PubMedID: 16513107OAI: oai:DiVA.org:umu-16927DiVA: diva2:156600
Available from: 2007-12-02 Created: 2007-12-02 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Neuroactive steroids and rat CNS
Open this publication in new window or tab >>Neuroactive steroids and rat CNS
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Several studies suggest profound effects on mood and cognition by neuroactive steroids. Estrogen alone or in combination with antidepressant drugs affecting the serotonin system has been used to treat mood disorders. On the other hand, progesterone is related to negative effects on mood and memory. A major part of the progesterone effects on the brain can be mediated by its metabolite allopregnanolone, which is also de novo synthesized in the brain, and affects the GABAA receptors. It would be of great importance to find a substance that antagonize allopregnanolone adverse effects.

To investigate how long term supplementation of estradiol and progesterone, resembling postmenopausal hormone replacement therapy, affects serotonin receptors in different brain areas important for mood and memory functions, we used ovariectomized female rats. After 2 weeks of supplementation with 17β-estradiol alone or in combination with progesterone, or placebo pellets, estradiol alone decreases but estradiol supplemented together with progesterone increases 5HT1A mRNA expression in the hippocampus. Estradiol decreases the 5HT2C receptor gene expression, while estradiol in combination with progesterone increases the 5HT2A mRNA expression in the ventral hippocampus. Thus, estradiol alone has opposite effects compared to the estradiol/progesterone combination. To detect if acute tolerance develops to allopregnanolone, an EEG method was used where male rats by continuous allopregnanolone infusion were kept on anesthesia level of the silent second (SS). After different time intervals (first SS, 30 min or 90 min of anesthesia) several GABAA receptor subunit mRNAs were measured for detecting if changed expression of any GABAA receptor subunits is involved in development of acute tolerance. There is development of acute tolerance to allopregnanolone and brain regions of importance are hippocampus, thalamus and hypothalamus. The GABAA receptor alpha4 subunit in thalamus and alpha2 subunit in the dorsal hippocampus are related to development of acute tolerance. For assessing allopregnanolone behavioral effects, we studied how this neurosteroid affects spatial learning in the Morris water maze task Allopregnanolone inhibits spatial learning short after the injection and shows a specific behavioral pattern with swimming close to the pool wall. The steroid UC1011 can inhibit the increase in chloride ion uptake induced by allopregnanolone. UC1011 decreases allopregnanoloneinduced impairment of spatial learning in the water maze, as well as the specific behavioral swim pattern.

In conclusion, the present work demonstrates that neuroactive steroids affect the 5HT and GABA systems in a brain region specific way. GABAA receptor subunit changes in hippocampus and thalamus are related to acute allopregnanolone tolerance. Allopregnanolone induces cognitive deficits, like spatial learning impairment and UC1011 can inhibit allopregnanolone-induced effects in vitro and in vivo.

Key words: Estradiol, progesterone, HRT, allopregnanolone, UC1011, serotonin receptor, GABAA receptor, mRNA, Morris water maze, silent second, tolerance.

Publisher
91 p.
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 898
Keyword
Estradiol, progesterone, HRT, allopregnanolone, UC1011, serotonin receptor, GABAA receptor, mRNA, Morris water maze, silent second, tolerance
Research subject
Clinical Neurophysiology
Identifiers
urn:nbn:se:umu:diva-296 (URN)91-7305-668-5 (ISBN)
Public defence
2004-09-16, E04, 6E, 09:00 (English)
Opponent
Available from: 2004-08-11 Created: 2004-08-11 Last updated: 2009-12-18Bibliographically approved
2. Tolerance and antagonism to allopregnanolone effects in the rat CNS
Open this publication in new window or tab >>Tolerance and antagonism to allopregnanolone effects in the rat CNS
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Many studies have suggested a relationship between sex steroids and negative mental and mood changes in women. Allopregnanolone, a potent endogenous ligand of the GABA-A receptor and a metabolite of progesterone, is one of the most accused neuroactive steroids. Variations in the levels of neuroactive steroids that influence the activity of the GABA-A receptor cause a vulnerability to mental and emotional pathology. In women, there are physiological conditions in which allopregnanolone production increases acutely (e.g. stress) or chronically (e.g. menstrual cycle, pregnancy), thus exposing the GABA-A receptor to high allopregnanolone concentrations. In such conditions, tolerance to allopregnanolone probably develops.

We have evaluated the 3β-hydroxy pregnane steroid UC1011 as a functional antagonist to allopregnanolone-induced negative effects in rats. In vivo, we used the Morris Water Maze (MWM) test of learning and, in vitro, we studied chloride ion uptake into cortical and hippocampal membrane preparations. The steroid UC1011 reduces the allopregnanolone-induced learning impairment in the MWM and the increase in chloride ion uptake induced by allopregnanolone. To detect whether chronic tolerance develops to an allopregnanolone-induced condition, male rats were pretreated with allopregnanolone injections for three or seven days. These rats were then tested in the Morris Water Maze for five days and compared with relevant controls. Rats with seven days’ allopregnanolone pretreatment experienced improved performance compared with the acutely allopregnanolone-exposed group, reflecting chronic tolerance development. To study the GABA-A receptor changes in acute allopregnanolone tolerance, we used the silent second (SS) anaesthesia threshold method. At acute tolerance, 90 minutes of anaesthesia, the abundance of the GABA-A receptor α4 subunit and the expression of the α4 subunit mRNA in the thalamus ventral-posteriomedial (VPM) nucleus were reduced. There was also a significant negative correlation between the increase in the allopregnanolone dose needed to maintain anaesthesia and the α4 mRNA in the VPM nucleus. We also investigated whether allopregnanolone tolerance was still present one or two days after the end of the anaesthesia-induced acute tolerance. Tolerance persisted to one day, but not two days, after the treatment and the α4 subunit mRNA expression in the VPM nucleus was negatively related to the allopregnanolone doses needed after one day.

In conclusion, the current thesis shows that the substance UC1011 can reduce the allopregnanolone-induced negative effects in the water maze test. Chronic allopregnanolone tolerance can develop to the effects of allopregnanolone. Allopregnanolone tolerance persists one day after the induction of acute allopregnanolone tolerance. The GABA-A receptor α4 subunit in the thalamus might be involved in the development and persistence of acute tolerance to allopregnanolone.

Place, publisher, year, edition, pages
Umeå: Klinisk vetenskap, 2006. 78 p.
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1026
Keyword
Allopregnanolone, GABA-A receptor, UC1011, Spatial memory, Morris Water Maze, Tolerance, Silent second, mRNA
National Category
Obstetrics, Gynecology and Reproductive Medicine
Identifiers
urn:nbn:se:umu:diva-804 (URN)91-7264-073-1 (ISBN)
Public defence
2006-09-15, Betula, 6M, NUS, Umeå, 09:00 (English)
Opponent
Supervisors
Available from: 2006-05-17 Created: 2006-05-17 Last updated: 2011-08-29Bibliographically approved
3. Progesterone metabolites: learning, tolerance, antagonism & metabolism
Open this publication in new window or tab >>Progesterone metabolites: learning, tolerance, antagonism & metabolism
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Progesterone metabolites as allopregnanolone, isoallopregnanolone and tetrahydrodeoxy-corticosterone (THDOC) are increased in the luteal phase of the menstrual cycle, throughout pregnancy and during stress. Allopregnanolone and THDOC are neurosteroids with 3α-hydroxy, 5α-configurations and positive modulating effect on the GABAA receptor. They have similar properties and effect, and share the same binding sites on the GABAA receptor. Isoallopregnanolone has a 3β-hydroxy, 5α-configuration and a diverse effect as a proposed antagonist to both allopregnanolone and THDOC. Neurosteroids are thought to exert their effect predominantly at extrasynaptic GABAA receptors, containing for example α4- or α5-subunits. Such receptors are involved in the tonic response. Different subunits have diverse distribution pattern in the brain and are involved in different functions. The α5-subunit, mainly expressed in the hippocampus, is involved in learning, while α4 is more widespread and involved in e.g. anxiety and anaesthesia.

The aim of the present thesis was to contribute to the knowledge about selected progesterone metabolites and their effects on learning and tolerance development, as well as their metabolism. Also basic characteristics between different α-subunits of the GABAA receptor were evaluated.

The thesis shows that the effect of bicuculline and pentobarbital is not dependent on the α-subunit isoform of the GABAA receptor expressed in oocytes. Acute tolerance developed after allopregnanolone-induced anaesthesia with a decrease at both mRNA and protein levels of the GABAA receptor α4-subunit in the thalamus VPM nucleus. A negative correlation between the α4 mRNA and the increased dose of allopregnanolone needed to maintain the anaesthesia level was also shown. In addition, allopregnanolone induces a learning impairment in the Morris water maze test, when high concentrations of allopregnanolone are present in the brain. This impairment is not possible to reverse by isoallopregnanolone. In α5β3γ2L-transfected HEK-293 cells THDOC induces a baseline shift of its own and also potentiate the GABA-current. Neither of those THDOC effects can be inhibited by isoallopregnanolone. Instead isoallopregnanolone shows an agonistic effect on the THDOC-potentiation of the GABA-response. The main allopregnanolone metabolites identified, 5α-DHP and isoallopregnanolone, as well as allopregnanolone itself are mainly localized to the brain after an i.v. injection. After an isoallopregnanolone injection there is a more even distribution of the given steroid and the metabolites between plasma and brain. There is an epimerisation between isoallopregnanolone and allopregnanolone and vice versa.

In conclusion, the present thesis shows that the α4-subunit in the thalamus VPM nucleus is likely to be involved in the acute tolerance development against allopregnanolone and that allopregnanolone-induced learning impairment is likely to be hippocampus dependent. The lack of antagonistic effect of isoallopregnanolone on the THDOC-induced α5β3γ2L-GABAA response, together with epimerisation of isoallopregnanolone to allopregnanolone, could explain why isoallopregnanolone does not work as an antagonist to the allopregnanolone-induced learning impairment in a hippocampus dependent learning task.

Place, publisher, year, edition, pages
Umeå: Umeå university, 2009. 73 p.
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1306
Keyword
allopregnanolone, isoallopregnanolone, THDOC, learning, tolerance, antagonism, inhibition, patch clamp, Morris water maze, metabolism, epimerization
National Category
Obstetrics, Gynecology and Reproductive Medicine
Research subject
Obstetrics and Gynaecology
Identifiers
urn:nbn:se:umu:diva-27064 (URN)978-91-7264-888-3 (ISBN)
Public defence
2009-12-05, Sal 914, By 1, 9 tr, NUS, Norrlands Universitetssjukhus, Umeå, 10:00 (English)
Opponent
Supervisors
Available from: 2009-11-16 Created: 2009-11-09 Last updated: 2010-01-18Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full textPubMedhttp://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Retrieve&list_uids=16513107&dopt=Citation

Search in DiVA

By author/editor
Türkmen, SahruhLindblad, CharlotteJohansson, Inga-MajBäckström, Torbjörn
By organisation
Obstetrics and GynaecologyPharmacology
In the same journal
European Journal of Pharmacology

Search outside of DiVA

GoogleGoogle Scholar

doi
pubmed
urn-nbn

Altmetric score

doi
pubmed
urn-nbn
Total: 118 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf