Effect of Sympathetic Blocking Agents on the Toxic Action of O₂ at High Pressure

¹ From the Department of Physiology, University of Michigan, Ann Arbor, Michigan

The effects of sympathetic blocking agents were studied on rats exposed to O₂ at 80 lb. gauge pressure. The ganglionic blocking agents TEAC and hexamethonium reduced the usual convulsive response, lung damage and mortality to a significant degree. On the other hand, the peripheral sympatholytic agents dibenamine, Dibenzyline, and SKF 501 (N-(9-fluorenyl)-N-ethyl-ß-chlorethylamine) lacked a notable effect on the somatic seizure but definitely reduced the pulmonary pathology and mortality. The drug SKF 501 was also found to protect animals exposed to O₂ at 80 lb. 80 mm Hg pCO₂. But this protection was seen only in the lungs, mortality was about the same as the normals simultaneously exposed. These experiments suggest that hyperactivity of the sympathetic nervous system is the factor primarily responsible for the pulmonary edema and congestion resultant from OHP. It is further indicated that this system also contributes significantly to the hyperoxic seizure and the incidence of mortality.

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