3-Carbamyl-N-allylquinuclidinium bromide. Effects on cholinergic activity and protection against soman

3-Carbamyl-N-allylquinuclidinium bromide (CAB) was synthesized and evaluated for its pharmacological effects on cholinergic activity and for protection in vivo against soman toxicity in guinea pigs. This carbamylated derivative of N-allyl-3-quinuclidinol (NAQ), a potent inhibitor of high-affinity choline uptake, demonstrated stereospecific alterations of cholinergic function as well as protection against soman. The R-isomer, but not the S-isomer, of CAB inhibited erythrocyte acetylcholinesterase (AChE) and plasma pseudocholinesterase (pChE) in a concentration-response manner (IC50 = 25 and 29 microM, respectively). The R-isomer of CAB was also a more potent inhibitor of high-affinity choline uptake (IC50 = 4.8 microM) than S-CAB (IC50 = 63 microM). When R-CAB (10 mumol/kg, i.m.) was administered to guinea pigs 30 min prior to soman in conjunction with atropine (16 mg/kg, i.m.) given 1 min post-soman, the compound significantly reduced lethality up to 5 LD50S. This represents enhanced protection when compared to NAQ (up to 100 mumol/kg); the S-isomer of CAB failed to protect against soman intoxication. The results demonstrate that reversible inhibition of AChE with suppression of acetylcholine synthesis into a single compound, CAB, enhances the protection against organophosphates.