Acetylcholine content in the brain of rats treated with paraoxon and obidoxime

Abstract

1 The effect of obidoxime on the rise in brain acetylcholine caused by the anticholinesterase paraoxon was studied in the rat. 2 In animals poisoned with a sublethal dose of paraoxon and thereafter treated with obidoxime the levels of both “free” and total brain acetylcholine were practically the same as those in rats injected with paraoxon only. 3 After poisoning with doses of paraoxon which are lethal unless an oxime is also given, the total acetylcholine in the brain of obidoxime-protected rats continued to accumulate, reaching a peak 2 h after injection of paraoxon. At this time no signs of central effects such as convulsions or tremor were seen. 4 Atropine, given 30 min before paraoxon, markedly reduced the rise in total brain acetylcholine seen when the anticholinesterase is given alone. 5 In rats pretreated with atropine and obidoxime excessive doses of paraoxon which are lethal in the absence of the antidotes produced a rise in total brain acetylcholine which was directly proportional to the dose of paraoxon administered.