EFFECTS OF CHIRONEX-FLECKERI TOXIN ON ISOLATED PERFUSED GUINEA-PIG HEART

The effects of toxin extracts from the cnidarian, Chironex fleckeri Southcott have been studied on the isolated, perfused guinea pig heart. Small doses of toxin resulted in reversible decreases in coronary flow, heart rate and amplitude of contraction whilst larger doses produced irreversible changes. Although the toxin did not appear to act at alpha or beta adrenergic receptors, catecholamines provided some protection. Serotonin was devoid of any protective action. Adenosine or ATP did not affect the changes in coronary flow or heart rate caused by the toxin, but reduced the amplitude changes. It is suggested that the different effects of the vasodilator agents on the toxin response are due to their differing sites of action within the coronary circulation. Stimulation of cardiac metabolism by the catecholamines and adenosine or ATP may also be a factor in the maintenance of cardiac contractility by these compounds in the presence of the toxin. The effects of the toxin on the isolated heart are correlated with those observed in previous experiments on the intact animal. © 1969.