Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 1 of 1
Full-Text Articles in Medical Toxicology
The Sea Anemone Purine, Caissarone: Adenosine Receptor Antagonism, Roland A. Cooper, Josecarlos De Freitas, Frank Porreca, Cynthia M. Eisenhour, Ronald Lukas, Ryan J. Huxtable
The Sea Anemone Purine, Caissarone: Adenosine Receptor Antagonism, Roland A. Cooper, Josecarlos De Freitas, Frank Porreca, Cynthia M. Eisenhour, Ronald Lukas, Ryan J. Huxtable
Roland A. Cooper
Caissarone, a sea anemone iminopurine, produced an increase in the twitch response of the electrically stimulated guinea-pig ileum-myenteric plexus. In the same assay, caissarone reduced the inhibitory response to the endogenous neuromodulator, adenosine, the A1 adenosine receptor agonist, R-phenylisopropyladenosine (R-PIA), and the A2 agonist, 5'-(N-cyclopropyl)-carboxamidoadenosine (CPCA) in a dose-dependent manner. Schild plot analysis of antagonism by caissarone yielded slopes of near unity, indicating that caissarone acts as a simple competitive antagonist at the adenosine receptor. The dissociation constants (KB) for caissarone ranged from 0.53 mM to 0.78 mM. In functional nicotinic receptor assays in two human cell lines, caissarone failed …