Toxins purified from laboratory cultures of Florida's red tide organism Gymnodinium breve will be administered to mice for periods of 4-6 weeks to examine subacute effects on living systems. Histopathology will be performed on individuals alive after the total administration period. The structure of the toxins will be examined by nmr, and by x-ray crystallography following preparation of suitable crystalline derivatives. Neurophysiological experiments will be performed to ascertain the site(s) of action of the purified toxins on isolated nerves.