Document Detail

Melatonin receptors in brain areas and ocular tissues of the teleost Tinca tinca: characterization and effect of temperature.
MedLine Citation:
PMID:  18177872     Owner:  NLM     Status:  MEDLINE    
The aim of the present study was to characterize the central melatonin receptors in brain areas and ocular tissues of the teleost Tinca tinca. We investigated the temperature-dependence of 2-iodo-melatonin ([(125)I]Mel) binding in the optic tectum-tegmentum area and the neural retina. The binding of [(125)I]Mel showed a widespread distribution in brain and ocular tissues, with the highest density in the optic tectum-thalamus and the lowest in hindbrain. The [(125)I]Mel affinity was similar in all the studied tissues, and it was on the order of the low pM range. Saturation, kinetic and pharmacological studies showed the presence of a unique MT(1)-like melatonin binding site. In addition, the non-hydrolysable GTP analog, the GTPgammaS, and sodium cations induced a specific binding decrease in the optic tectum and neural retina, suggesting that such melatonin binding sites in the tench are coupled to G protein. Thus, these melatonin binding sites in optic tectum and neural retina fulfil the requirements of a real hormone receptor, the specific binding is rapid, saturable, and reversible, and is inhibited by GTP analogs. Additionally, a clear effect of temperature on such central melatonin receptors was found. Temperature did not modify the B(max) and K(d), but the kinetics of [(125)I]Mel binding resulted in a highly thermosensitive process in both tissues. Both association and dissociation rates (K(+1) and K(-1)) significantly increased with assay temperature (15-30 degrees C), but the K(d) constant (estimated as K(-1)/K(+1)) remained unaltered. In conclusion, this high thermal dependence of the melatonin binding to its receptors in the tench central nervous system supports the conclusion that temperature plays a key role in melatonin signal transduction in fish.
M A López Patiño; A L Alonso-Gómez; A Guijarro; E Isorna; M J Delgado
Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2007-11-22
Journal Detail:
Title:  General and comparative endocrinology     Volume:  155     ISSN:  0016-6480     ISO Abbreviation:  Gen. Comp. Endocrinol.     Publication Date:  2008 Feb 
Date Detail:
Created Date:  2008-02-11     Completed Date:  2008-05-01     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0370735     Medline TA:  Gen Comp Endocrinol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  847-56     Citation Subset:  IM    
Departamento de Fisiología (Fisiología Animal II), Facultad de Biología, Universidad Complutense, 28040 Madrid, Spain.
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MeSH Terms
Binding Sites
Body Temperature / physiology
Brain / metabolism*
Cyprinidae / metabolism*
Eye / metabolism*
Guanosine 5'-O-(3-Thiotriphosphate) / pharmacology
Iodine Radioisotopes / pharmacokinetics
Melatonin / metabolism,  pharmacokinetics
Protein Binding / drug effects
Receptors, Melatonin / metabolism*
Sodium / pharmacology
Reg. No./Substance:
0/Iodine Radioisotopes; 0/Receptors, Melatonin; 37589-80-3/Guanosine 5'-O-(3-Thiotriphosphate); 73-31-4/Melatonin; 7440-23-5/Sodium

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