Effects of acute administration of soman on spinal cord reflexes in the cat

The acute effects of the organophosphorus acetylcholinesterase inhibitor, soman, was studied on spinal cord reflexes in the spinal cord transected cat. It was found that doses of 10 micrograms/kg significantly altered the monosynaptic and dorsal root reflexes by causing an initial depression lasting about 20 min followed by a later facilitation lasting over 3 h. A higher dose of soman (20 micrograms/kg) caused the initial depression but did not produce the later facilitation. Cholinergic antagonists were used to determine whether these changes were related to inhibition of acetylcholinesterase or whether they were non-specific. It was found that mecamylamine blocked the depression and the facilitation while atropine depressed the spinal cord potentials. These data show that acute administration of 10 micrograms/kg soman produces specific effects on spinal cord reflexes which could be characterized as resulting from inhibition of acetylcholinesterase similar to the carbamate inhibitor, physostigmine.