CARDIOVASCULAR AND RESPIRATORY CHANGES FOLLOWING EXPOSURE TO A SYNTHETIC TOXIN OF PTYCHODISCUS-BREVIS

The present study demonstrated cardiorespiratory effects of a syntheti c phosphorus-containing ichthyotoxic metabolite elaborated by the mari ne dinoflagellate Ptychodiscus brevis in anaesthetised cats. The metab olite at a dose of 0.25-1.5 mg/kg i.v., resulted in a dose-dependent f all in blood pressure and such vasodepressor effect was associated wit h bradycardia. There is initial respiratory apnoea followed by increas ed rate and depth of respiration (hyperapnoea) following the administr ation of the toxin. The hypotensive response was accompanied by a decr ease in aortic baroreceptor activity. The ECG showed atrioventricular conduction block, arrhythmia and depression of S-T segment and T wave which indicated coronary insufficiency. Vasodepressive property of the toxin is presumably muscarinic in nature as atropine counteracted the vasodepression.