The Sea Anemone Purine Caissarone: Adenosine Receptor Antagonism

Department

neurobiology

Document Type

Article

Abstract

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 either to potentiate or to reduce carbamylcholine-mediated 86Rb+ efflux. Thus, the enhancing activity of caissarone on the gut could not be attributed to activity at the ganglionic nicotinic receptor. Based on structure and pharmacological activity, caissarone appears to be the first marine product described as an adenosine receptor antagonist. © 1995.

Publication Date

1-1-1995

Publication Title

Toxicon

ISSN

00410101

Volume

33

Issue

8

First Page

1025

Last Page

1031

Digital Object Identifier (DOI)

10.1016/0041-0101(95)00047-P

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