THE EFFECT OF CHRONIC POISONING WITH DI-ISOPROPYL FLUOROPHOSPHATE ON NEUROMUSCULAR FUNCTION IN THE CAT

¹ Department of Pharmacology of Cornell University Medical College, New York City

1. The daily intramuscular injection of DFP in cats, resulted in the appearance of ataxia, extreme muscular weakness, and generalized fasciculations. Subsequent to this it was possible to demonstrate weakness and fatigableness by means of forced exercise. Finally, a recurrent weakness appeared in the hind limbs and lasted for as long as 147 days.

2. The cholinesterase activity of brain, nerve, and muscle has been measured at intervals after poisoning. The symptomatic recovery of the poisoned cat approximates the regeneration of the tissue esterases.

3. The response of the gastrocnemius muscle to the intra-arterial injection of acetylcholine was altered in the poisoned animals. This consisted of an increased sensitivity to acetylcholine and a prolongation of the contractile response resembling that seen in denervated muscle.

4. The muscle of the poisoned cat manifests an impaired ability to maintain a tetanus as compared to normal animals.

5. It is concluded that the syndrome described results from the extreme reduction of the muscle and nervous tissues cholinesterase by DFP. The changes in the response of the muscle to acetylcholine following protracted inactivation of cholinesterase, suggest the development of an injury at the myoneural junction resembling that associated with denervation.

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