Effects of pyridostigmine and cholinolytics on cholinesterase and acetylcholine in Soman poisoned rats.

Soman reduced blood and brain cholinesterase (ChE) activity to less than 15% and increased cerebral acetylcholine (ACh) levels to 137.4% of control. When pyridostigmine (P) was used as a prophylactic adjunct, it reduced blood ChE activity to 31.6% of control, failed to significantly alter brain ChE activity, and protected more than 70% of the blood (but not brain enzyme) from phosphonylation by soman. Benactyzine (B) was more effective than atropine (A) in reducing cerebral ACh concentrations, while a combination of the two was more effective than either alone. A prophylaxis of P + A + B was effective in controlling ACh levels in rats poisoned with one LD50 dose of Soman. Since P did not diminish the effects of the cholinolytics on cerebral ACh, this (together with the enzyme data) suggests that the two cholinolytics alone provided the central protection.