Oxygen at 2 atmospheres absolute pressure does not increase the radiation sensitivity of normal brain in rats

Cranial radiation was administered to CD Fisher rats at 1.0, 1.5 and 2.0 atmospheres absolute oxygen pressure. Life span following radiation was recorded. Surviving animals were killed at 28 weeks and the brains were examined independently by two neuropathologists. Survival time was significantly less in animals receiving higher doses of radiation but showed no relationship to the oxygen pressure in the environment of the animal at the time radiation was administered. Microscopic examination of the brain did not reveal any differences in animals radiated in a normobaric or hyperbaric oxygen environment. It is concluded that hyperbaric oxygen does not sensitize the normal brain to the effects of ionizing radiation.