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1. To study the influence of pharmacological pretreatment (PANPAL or pyridostigmine combined with biperiden) and antidotal treatment (the oxime HI-6 plus atropine) on soman-induced neurotoxicity, male albino rats were poisoned with a lethal dose of soman (54 (g/kg i.m.; 100% of LD50 value) and observed at 24 hours and 7 days following soman challenge. The neurotoxicity of soman was evaluated using a Functional observational battery and an automatic measurement of motor activity. 2. Pharmacological pretreatment as well as antidotal treatment were able to eliminate some of soman-induced neurotoxic effects observed at 24 hours following soman poisoning. The combination of pharmacological pretreatment (PANPAL or pyridostigmine combined with biperiden) and antidotal treatment was found to be more effective in the elimination of soman-induced neurotoxicity in rats at 24 hours following soman challenge in comparison with the administration of pharmacological pretreatment or antidotal treatment alone. To compare both pharmacological pretreatments, the combination of pyridostigmine with biperiden seems to be more efficacious to eliminate soman-induced signs of neurotoxicity than PANPAL. 3. At 7 days following soman poisoning, the combination of pharmacological pretreatment involving pyridostigmine and biperiden with antidotal treatment was only able to completely eliminate somaninduced neurotoxic signs. 4. Thus, our findings confirm that the combination of pharmacological pretreatment and antidotal treatment is able not only to protect the experimental animals from the lethal effects of soman but also to eliminate most soman-induced signs of neurotoxicity in poisoned rats. The pharmacological pretreatment containing pyridostigmine and biperiden appears to be more efficacious to eliminate soman-induced neurotoxic sings than PANPAL.

The ability of two types of pharmacological pretreatment (pyridostigmine alone or pyridostigmine in combination with two anticholinergic drugs) to increase the resistance of rats and mice against tabun and to increase the therapeutic efficacy of common antidotal treatment of tabun-poisoned rats and mice was compared. A significant decrease in the LD50 values of tabun was observed when mice as well as rats were pretreated with the prophylactic antidotal mixture consisting of pyridostigmine, benactyzine and trihexyphenidyle, designated PANPAL. Pyridostigmine-pretreated rats were also more resistant against acute lethal effects of tabun but pyridostigmine-induced resistance of rats was not so high as PANPAL-induced resistance. In addition, the pharmacological pretreatment with pyridostigmine alone was not able to protect mice against tabun-induced acute toxicity. The pharmacological pretreatment with pyridostigmine alone was able to increase the efficacy of currently used antidotal treatment (obidoxime in combination with atropine and diazepam) of tabun-induced poisoning, but PANPAL-induced increase in the efficacy of the same antidotal treatment was significantly higher than an increase induced by pyridostigmine alone. PANPAL-induced increase in the efficacy of antidotal treatment of tabun poisoning was also observed in mice. These findings confirm that PANPAL pretreatment of tabun-poisoned rats and mice seems to be much more suitable than currently used pyridostigmine alone. [Copyright &y& Elsevier]