A rather alarming possibility came to light during the annual meeting in November of the Society for Neuroscience, in New Orleans. Researchers at Emory university, Georgia, reported that repeated injections of rotenone in rats caused symptoms resembling those of Parkinson's disease, including difficulty in walking and shakiness of the extremities, accompanied by protein deposits in brain cells.
According to an account in Science for November 10, rotenone has a structure similar to that of tetrahydropyridine, a compound found to be responsible for Parkinsonian effects in diamorphine addicts who had injected a product contaminated with it. A metabolite of tetrahydropyridine which is also produced by rotenone, interferes with electron transport in cell mitochondria, releasing free radicals which kill the cells.
Rotenone is insecticidal and has been used in agriculture to control lice, fleas and various larvae. It has been considered safe because it is relatively harmless when ingested by warm-blooded animals. It has shown anticancer activity against lymphocytic leukaemia and epidermoid nasopharyngeal carcinoma, although in some circumstances it has been shown to induce cancers. It is widely used in the form of sprays, which raises some concern because its inhalation is known to be more harmful than its ingestion. In Central and South America, rotenone, in the form of extracts of the Jamaica dogwood (Piscidia erythrina) and other plants, has been widely used in primitive communities to poison fish. Rotenone is the latest suggestion to account for Parkinson's disease, but there are several distinct alternative explanations which probably carry more weight.