Humans eating contaminated seafood develop symptoms including vomiting nausea, diarrhea and abdominal cramps. In severe cases, the toxin leads to neurological damage, characterized by headaches, confusion, coma and even death. Exposure can also cause amnesic shellfish poisoning, characterized by permanent loss of short-term memory.
Since the discovery of domoic acid on the West Coast, officials there collect regular samples of affected marine animals, including razor clams and Dungeness crabs. Fisheries are closed when domoic acid levels reach 20 parts per million (ppm) in the animals' tissues, the level at which the FDA deems the toxin unsafe for human consumption.
Earlier studies in animals have focused on lethal and highly toxic doses of domoic acid. Such exposures cause extensive damage to the hippocampus, a part of the brain involved in learning and memory. More recent reports examining the effects of a range of doses have found highly reproducible behavioral consequences of sublethal doses of the marine toxin, including impairments to spatial memory.
To explore the toxin's effects during development, the Duke team administered domoic acid to pregnant rats at three levels -- each below those found to cause convulsions or fetal loss. Others animals did not receive the toxin. The researchers then conducted a battery of behavioral tests on the exposed and normal animals to determine the effects of early domoic acid on movement and working memory.
Rats with a history of domoic acid exposure showed greater initial activity in a maze test than control rats, followed by a rapid decline. Moreover, domoic acid exposure affected cognitive function in complex ways, the researchers reported.
Toxin exposure decreased the normal difference between male and female rats in their ability to complete
Source:Duke University Medical Center