CENTRAL-NERVOUS-SYSTEM TOXICITY OF MANGANESE .1. INHIBITION OF SPONTANEOUS MOTOR-ACTIVITY IN RATS AFTER INTRATHECAL ADMINISTRATION OF MANGANESE CHLORIDE

The intrathecal administration of MnCl2 to young male rats caused dopa mine depletion in the caudate-putamen and a decrease in spontaneous mo tor activity. Our experiments demonstrate that in the young rat: (a) t he lateral choroid plexus protects the cerebrospinal fluid (CSF) from high concentrations of Mn in the blood by sequestering and thus preven ting large amounts of this metal ion from entering the CSF. As blood M n levels rise, the lateral choroid plexus may become overwhelmed and l eak an increasing amount of Mn into the CSF. (b) The lateral choroid p lexus does not remove Mn2+ from the CSF. (c) The injection of MnCl2 in to the CSF of rats caused a rapid decrease in spontaneous motor activi ty which is dose-dependent and reversible under the present experiment al conditions. Intrathecal Mn results in a substantial decrease in str iatal dopamine but not homovanillic acid or 3,4-dihydroxyphenylacetic acid (DOPAC) concentrations and is associated with an increase in the Mn concentration of the substantia nigra and caudate-putamen. (C) 1995 Society of Toxicology.