THE ERGOT ALKALOIDS
alkaloids are produced by Claviceps
purpurea, a fungus that infects grasses and grains—especially rye—under
damp growing or storage conditions. This fungus synthesizes histamine,
acetyl-choline, tyramine, and other biologically active products in addi-tion
to a score or more of unique ergot alkaloids. These alkaloids affect α adrenoceptors,
dopamine receptors, 5-HT receptors, and perhaps other receptor types. Similar
alkaloids are produced by fungi parasitic to a number of other grass-like plants.
accidental ingestion of ergot alkaloids in contaminated grain can be traced
back more than 2000 years from descriptions of epidemics of ergot poisoning ( ergotism). The most dramatic effects of
poisoning are dementia with florid hallucinations; pro-longed vasospasm, which
may result in gangrene; and stimulation of uterine smooth muscle, which in
pregnancy may result in abortion. In medieval times, ergot poisoning was called
St. Anthony’s fire after the saint
whose help was sought in reliev-ing the burning pain of vasospastic ischemia.
Identifiable epi-demics have occurred sporadically up to modern times (see Box:
Ergot Poisoning: Not Just an Ancient Disease) and mandate con-tinuous
surveillance of all grains used for food. Poisoning of graz-ing animals is
common in many areas because the fungi may grow on pasture grasses.
addition to the effects noted above, the ergot alkaloids pro-duce a variety of
other central nervous system and peripheral effects. Detailed
structure-activity analysis and appropriate semi-synthetic modifications have
yielded a large number of agents of experimental and clinical interest.