Abstract
—The toxic skin tubercle gland secretion of the stonefish, Synanceia trachynis, contains a smooth muscle antispasmogen that is readily distinguished from papaverine, verapamil and both α and β adrenoreceptor agonists. At 15 μg/ml, the toxin containing fraction markedly inhibited the phasic response and had a lesser inhibitory effect on the tonic response of acetylcholine- and KCl-induced contractures of guinea-pig ileum, while at 50 μg/ml, the toxin markedly inhibited both responses. Over the same dose range the toxin fraction markedly inhibited BaCl 2-induced contractile responses but did not distinguish between the phasic and tonic components. Whereas the toxin fraction markedly reduced the tone of previously induced supramaximal KCl and acetylcholine responses of guinea-pig ileum, it had little effect on the tone of previously induced BaCl 2 responses. The toxin non-competitively inhibited acetylcholine-induced contractions of guinea-pig ileum and similarly non-competitively inhibited the response induced by Ca 2+ in high-[K +] Ringer. The toxin is not a chelating agent for Ca 2+ or Mg 2+ and it does not affect ATP-induced contracture of glycerinated guinea-pig ileum. The antispasmogenic effect of the toxin contained in the fraction does not result from inhibition of cAMP phosphodiesterase activity.
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