CHOLINERGIC RESPONSE IN THE HEART OF THE CLAM MERCENARIA-MERCENARIA - ACTIVATION BY CONUS-CALIFORNICUS VENOM COMPONENT

The spontaneously beating heart of the clam Mercenaria mercenaria is inhibited by an extract from the venom of the marine snail Conus californicus (Fig. 1). This inhibition is antagonized by benzoquinonium, tetraethylammonium, phenyltrimethylammonium and methylxylocholine (Fig. 2), all of which antagonize cholinergic inhibition of Mercenaria heart, and is not blocked by d-tubocurarine, hexamethonium, atropine, or α-Bungarotoxin (Fig. 3). In addition, cholinergic inhibition of Mercenaria heart is mimicked by arecoline, blocked by methylxylocholine (Fig. 2) and phenyltrimethylammonium, and not significantly affected by hexamethonium or α-Bungarotoxin. It is proposed that the Conus venom agent inhibits Mercenaria heart by activation of the cholinergic response of the heart. It is also concluded that the cholinergic response in Mercenaria heart is pharmacologically identical to the slow, potassium-mediated hyperpolarizing cholinergic response found on Aplysia neurons (Table 1). © 1979 Springer-Verlag.