liu.seSearch for publications in DiVA
Change search
ReferencesLink to record
Permanent link

Direct link
Melanophore a2-Adrenoceptors.
Linköping University, Department of Medicine and Care, Clinical Pharmacology. Linköping University, Faculty of Health Sciences.
1993 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The present study provides new insight into the pharmacology, the signal transduction mechanisms and the molecular biology of a2-adrenoceptors (a2-ARs) in black pigment cells (melanophores) of a teleost fish, the cuckoo wrasse (Labrus ossifagus L.). Stimulation of these receptors leads to an aggregation of intracellular pigment granules, which is the cellular mechanism underlying the ability of fishes to change color.

The pharmacology of the melanophore a2-AR is very similar to its mammalian counterparts. However, the melanophore a2-AR is unique in one respect, UK 14,304, a potent agonist at mammalian a2-ARs, is an antagonist in melanophores.

Noradrenaline and the selective a2-AR agonist B-HT 920 are pharmacologically heterogeneous regarding their ability to induce pigment aggregation. This may reflect that B-HT 920 and noradrenaline interact with different a2-AR sites.

Pigment aggregation induced by a2-ARs seems to involve multiplesignaling pathways. Attenuation of intracellular cAMP production and a subsequent reduction of protein kinase A activity may serve as one mechanism, and an additional signal mechanism may involve activation of a phosphatase.

An a2-adrenoceptor (a2p) from L. ossifagus skin mRNA was cloned. The deduced amino acid sequence showed significant homology with the human a2-ARs. When expressed in a mammalian cell line, the pharmacology of the <X2F was found to be very similar that of the in situ melanophore a2-ARs. The <X2F showed characteristics of both the human a2CIO and a2C4, indicating that <X2F may represent traces of an ancestral subtype.

Melanin-concentrating hormone (MCH) induces pigment aggregationthrough a unique receptor. However, MCH receptors and a2-ARs might share a common signal transduction mechanism, namely attenuation of cAMP production.

When melanophores are maintained in tissue culture media, the sensitivity to noradrenaline is increased and the sensitivity to MCH is decreased. This reciprocal change in sensitivity may be due to an increase in a2-AR coupling at the expense of MCH receptor couplingand/or to a down regulation of MCH receptors.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet , 1993. , 66 p.
Linköping University Medical Dissertations, ISSN 0345-0082 ; 396
National Category
Medical and Health Sciences
URN: urn:nbn:se:liu:diva-27545Local ID: 12205ISBN: 91-7870-937-7OAI: diva2:248097
Public defence
1993-09-17, Berzeliussalen, Universitetssjukhuset, Linköping, 13:00 (Swedish)
Papers, included in the Ph.D. thesis, are not registered and included in the posts from 1999 and backwards.Available from: 2009-10-08 Created: 2009-10-08 Last updated: 2012-07-23Bibliographically approved

Open Access in DiVA

No full text

Search in DiVA

By author/editor
Svensson, Samuel
By organisation
Clinical PharmacologyFaculty of Health Sciences
Medical and Health Sciences

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Total: 43 hits
ReferencesLink to record
Permanent link

Direct link