Changes of acetylcholinesterase activity in various parts of brain following nontreated and treated soman poisoning in rats.

Changes of acetylcholinesterase (AChE) activity in various parts of the brain (frontal cortex, medulla oblongata, pons Varoli, cerebellum, hypothalamus, and hippocampus), following im sublethal non-treated and treated soman poisoning were studied. As a treatment, two antidotal mixtures containing atropine and either obidoxime or oxime HI-6 were used. This antidotal treatment was administered im for 30 s following soman intoxication. The AChE activities in the various brain tissues were evaluated at 1 and 3 h following soman administration. As expected, the highly toxic organophosphorus compound, soman, markedly inhibited AChE activity in all the brain sections at both time intervals. Both oximes had little influence on soman-induced AChE inhibition, but only the HI-6 mixture was able to reactivate soman-inhibited AChE significantly in some of the brain parts (frontal cortex, pons Varoli, hypothalamus). In the brain, the effect of HI-6 against soman-induced AChE inhibition is higher in comparison with obidoxime, but not quite satisfactory. Despite its limited effectiveness in the brain, HI-6 seems to be the most effective oxime yet found against soman poisoning because of its high reactivating effect in the peripheral compartment and other beneficial effects.