Influence of the organophosphorus compound DFP on inhibitory motor systems and esterase activity in the spinal cord of cats.

In high spinal cats, the acute time-dependent changes of both the activity of spinal reflex pathways and the activity of three different esterases (acetylcholinesterase, carboxylesterase and neurotoxicant target enzyme) in the spinal cord were investigated after intravenous application of the organophosphorus compound di-isopropyl phosphofluoridate (DFP). There is no general depression of spinal reflexes by DFP. While the recurrent inhibition is completely abolished for a long time and the reflexes to a flexor (PBSt) are depressed but with a shorter recovery time, the reflexes to an extensor (GS) are distinctly less depressed or even facilitated. Reflex pathways from skin afferents to motoneurones did not react in a uniform way to DFP, e.g. inhibitory nociceptive pathways were less affected than excitatory ones. Esterase activities were heavily depressed and recovered with different time courses. The acute DFP action cannot be explained by a uniform intoxication of all spinal functions but probably emerges from a differential action on different interneuronal systems.