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Characterization of HCN and cardiac function in a colonial ascidian.
MedLine Citation:
PMID:  21770038     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
Hyperpolarization-activated, cyclic nucleotide-gated (HCN) channels generate the rhythmic beating of mammalian hearts. We identified an HCN homolog in the colonial ascidian Botryllus schlosseri, a nonvertebrate chordate which possesses a tubular heart that beats bidirectionally. Contractions initiate at one end of the heart and travel across the length of the organ, and these periodically reverse, suggesting the presence of two pacemakers, one on each side. We find that HCN expression is highly enriched in cells scattered throughout the myocardium. We functionally analyzed the role of HCN channels in heartbeat using the antagonists Cilobradine and Zatebradine, which decreased the heartbeat in a reversible manner. We also assessed the role of β-adrenoreceptors in regulating HCN function using the antagonist Metoprolol, which lowered heartbeat rate (HR), as well as the agonist Isoproterenol, which did not alter HR, but caused simultaneous beating, analogous to a fibrillation. Measurements of direction and velocity of blood flow by making use of a novel system to study heart function in model systems amenable to live imaging revealed a significant correlation between heartbeat arrhythmia and drug treatment, similar to that observed with the same drugs in vertebrates. These results suggest that the heart pacemaker in tunicates may be homologous to that in their vertebrate counterparts in both development and function. J. Exp. Zool. 313A, 2011. © 2011 Wiley-Liss, Inc.
Authors:
Annette Hellbach; Stefano Tiozzo; Jungho Ohn; Michael Liebling; Anthony W De Tomaso
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2011-7-18
Journal Detail:
Title:  Journal of experimental zoology. Part A, Ecological genetics and physiology     Volume:  -     ISSN:  1932-5231     ISO Abbreviation:  -     Publication Date:  2011 Jul 
Date Detail:
Created Date:  2011-7-19     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101297745     Medline TA:  J Exp Zool A Ecol Genet Physiol     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Copyright Information:
Copyright © 2011 Wiley-Liss, Inc., A Wiley Company.
Affiliation:
Department of Molecular Medicine, Max Planck Institute of Biochemistry, Martinsried, Germany; Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, California. hellbach@biochem.mpg.de.
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