QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

This Article Full Text (PDF) References Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Willoughby, D. Articles by Benjamin, P. R. Search for Related Content PubMed PubMed Citation Articles by Willoughby, D. Articles by Benjamin, P. R. Social Bookmarking                         What's this?

Journal of Experimental Biology, Vol 202, Issue 19 2595-2607, Copyright © 1999 by Company of Biologists

JOURNAL ARTICLES

Cyclic AMP is involved in cardioregulation by multiple neuropeptides encoded on the FMRFamide gene

D Willoughby, MS Yeoman and PR Benjamin
Sussex Centre for Neuroscience, School of Biological Sciences, University of Sussex, Brighton BN1 9QG, UK. dw212@cam.ac.uk.

We have used a combination of biochemical and pharmacological techniques to investigate the role of the cyclic nucleotides, 3', 5'-cyclic adenosine monophosphate (cyclic AMP) and 3',5'-cyclic guanosine monophosphate (cyclic GMP), in mediating the cardioregulatory effects of FMRFamide and other neuropeptides encoded on exon II of the FMRFamide gene of Lymnaea stagnalis. The 'isoleucine' peptides (EFLRIamide and pQFYRIamide) produced complex biphasic effects on the frequency, force of contraction and tonus of the isolated heart of L. stagnalis, which were dependent on adenylate cyclase (AC) activity of the heart tissue. At a control rate of cyclic AMP production of less than or equal to 10 pmoles min(-)(1 )mg(-)(1) protein, the 'isoleucine' peptides produced a significant increase in AC activity in heart membrane preparations. This suggested that the enhanced AC activity is responsible for the stimulatory effects of the 'isoleucine' peptides on frequency and force of contraction of heart beat. This excitation sometimes followed an initial 'inhibitory phase' where the frequency of beat, force of contraction and tonus of the heart were reduced by the 'isoleucine' peptides. Hearts that showed the inhibitory phase of the 'isoleucine' response, but characteristically lacked the delayed excitatory phase, were found to have high levels of membrane AC activity (breve)10 pmoles min(-)(1 )mg(-)(1) protein in controls. Application of the 'isoleucine' peptides to membrane homogenate preparation from these hearts failed to increase AC activity. The addition of FMRFamide produced significant increases in the rate of cyclic AMP production in the heart membrane preparations, which could account, at least in part, for the cardioexcitatory effects of this peptide in the isolated whole heart. A membrane-permeable cyclic AMP analogue (8-bromo-cyclic AMP) and an AC activator (forskolin) were also cardioexcitatory. The peptide SEEPLY had no effects on the beat properties of the isolated heart and did not alter AC activity. The activity of the membrane-bound (particulate) guanylate cyclase (GC) was not significantly affected by any of the peptides.
CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    Twitter    What's this?

This article has been cited by other articles:

				D. Park, S. R. Zawacki, and H. L. Eisthen Olfactory Signal Modulation by Molluscan Cardioexcitatory Tetrapeptide (FMRFamide) in Axolotls (Ambystoma mexicanum) Chem Senses, May 1, 2003; 28(4): 339 - 348. [Abstract] [Full Text] [PDF]

				S. J. Perry, V. A. Straub, M. G. Schofield, J. F. Burke, and P. R. Benjamin Neuronal Expression of an FMRFamide-Gated Na+ Channel and Its Modulation by Acid pH J. Neurosci., August 1, 2001; 21(15): 5559 - 5567. [Abstract] [Full Text] [PDF]