Electroencephalographic and Behavioral Studies of Monomethyl Hydrazine Toxicity in the Cat

  • M. B. Sterman
  • R. W. LoPresti
  • M. D. Fairchild


The toxicity of monomethyl hydrazine (MMH) administered intraperitoneally in the cat was studied by reference to behavioral and neurophysiological indices. The acute lethal toxicity value (LD50) for MMH was established at 15 mg=kg, and the convulsive toxicity value (CD50) at 7m=kg. Doses of 18, 9, and 5mg=kg were then studied systematically in an effort to classify lethal, convulsive, and subconvulsive symptoms. For these doses, a preconvulsive syndrome was described involving recurrent and sustained symptoms, including vomiting, panting, rapid respiration, viscous salivation, hyperactivity, and subcortical seizure activity. The onset latency of these symptoms was directly related to dose. Several lines of evidence suggested at least a partial independence between biochemical and neurophysiological events responsible, on one hand, for convulsions and, on the other, for this preconvulsive syndrome. Convulsions were specifically delayed or prevented in animals trained to suppress movement through the use of a special EEG conditioning technique.