Acetylcholinesterase fluctuations in central nervous system of rat during methylmercury intoxication and chelation therapy.

A daily dose of 1 mg/kg and 10 mg/kg of methylmercury chloride (MMC) was injected to separate sets of rats for 2 days, 7 days, and 15 days. Low and high doses of four MMC antagonists, namely N-acetyl-DL-homocysteine thiolactone (NAHT), glutathione (GSH), D-penicillamine (DPA), and sodium selenite (SEL) were injected intramuscularly (i.m.) to MMC-treated animals after an interval of half an hour. The animals were sacrificed on the 3rd, 8th, and 16th day, respectively. An additional group of rats was treated with MMC for 7 days; thereafter, it was kept free of toxic exposure for 7 days and sacrificed on the 15th day. The brain was dissected and separated into olfactory bulbs, cerebral hemispheres, cerebellum, and medulla oblongata. Each part of the central nervous system (CNS) was studied separately. We found a dose- and duration-related acetylcholinesterase (AChE) inhibition in all CNS areas. The use of antagonists showed different effects in different CNS areas, but no appreciable recovery of AChE activity could be obtained with the doses used.