These studies investigated the effectiveness of combination treatment with a benzodiazepine and an anticholinergic drug against soman-induced seizures. The anticholinergic drugs considered were biperiden, scopolamine, trihexaphenidyl, and procyclidine; the benzodiazepines were diazepam and midazolam. Male guinea pigs were implanted surgically with cortical screw electrodes. Electrocorticograms were displayed continually and recorded on a computerized electroencephalographic system. Pyridostigmine (0.026 mg x kg(-1), i.m.) was injected as a pretreatment to inhibit red blood cell acetylcholinesterase by 30-40%. Thirty minutes after pyridostigmine, 2 x LD50 (56 microg x kg(-1)) of soman was injected s.c., followed 1 min later by i.m. treatment with atropine (2 mg x kg(-1)) + 2-PAM (25 mg x kg(-1)). Electrographic seizures occurred in all animals. Anticonvulsant treatment combinations were administered i.m. at 5 or 40 min after seizure onset. Treatment consisted of diazepam or midazolam plus one of the above-mentioned anticholinergic drugs. All doses of the treatment compounds exhibited little or no antiseizure efficacy when given individually. The combination of a benzodiazepine and an anticholinergic drug was effective in terminating soman-induced seizure, whether given 5 or 40 min after seizure onset. The results suggest a strong synergistic effect of combining benzodiazepines with centrally active anticholinergic drugs and support the concept of using an adjunct to supplement diazepam for the treatment of nerve-agent-induced seizures.

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The CD1-haired mouse and the SKH-hairless mouse are two animal models that have been used to evaluate sulfur mustard (HD) exposure and protection in our laboratory. In a recent study we observed that a substance P inhibitor protected the haired mouse ear against an HD solution, but the same drug was not successful in protecting the hairless mouse against HD vapor. This experiment prompted us to compare HD exposures between these models. We determined the (14)C content in the skin after exposures to HD containing (14)C-HD. Rate curves were generated for applications of (1) HD in methylene chloride to the haired mouse ear; (2) HD in methylene chloride to the hairless mouse dorsal skin; and (3) saturated HD vapor to the hairless mouse dorsal skin for 6 min. The curves showed a reduction in (14)C disintegrations per min in animals euthanized 0 to 2 h postexposure. The largest percentage of decrease of (14)C content in skin occurred within 30 min of HD challenge for all exposures. An 8-mm skin-punch biopsy and a 14-mm annular skin section surrounding the region of the 8-mm skin punch were taken from the hairless mouse dorsal skin exposed to HD in methylene chloride. The ratio of the (14)C content in the 8-mm skin punch to that in the surrounding 14-mm annular skin section was 7.3, demonstrating that the HD application spreads beyond the initially biopsied site. A concentration/time value of 6.3 mug/cm(2)/min was determined by counting skin (14)C disintegrations per minute in animals euthanized immediately after exposure to saturated HD vapor. Determinations of the amount of HD showed that similar quantities of HD, 0.4 mg, were detected on each model. These results contribute to a better quantitative understanding of HD application in the haired and hairless mouse models.