A brief history of the neurobehavioral toxicity of manganese: Some unanswered questions

It was observed by Couper in 1837 that manganese dust produces a neurologic al syndrome characterized by muscle weakness, tremor, bent posture, whisper ed speech and excess salivation. The similarity of these symptoms to those of Parkinson's disease were not recognized for many years. In addition to i ts Parkinson-like effects, manganese produces behavioral symptoms in humans including nervousness, hallucinations. memory loss, cognitive problems, bi zarre behaviors and flight of ideas. Despite these signs and symptoms, ther e have been few systematic attempts to study the effects of manganese on be havior using animal models. The need to better understand the effects of ma nganese on behavior is becoming more important due to the potential of incr eased environmental exposure to manganese due to its use, or proposed use a s a gasoline additive in a number of countries. However, there is debate as to which manganese compounds should receive priority for testing, what rou te of administration should be used in this testing, what dosing regimens s hould be used, what species are appropriate for behavioral testing, and wha t behavioral tests should be selected. Research to answer these questions i s needed so that the behavioral effects of manganese can be described compr ehensively and the mechanisms underlying these effects can be understood. ( C) 1999 Inter Press, Inc.