The studies were carried out to investigate the changes in the ammonia content of brain, liver, and blood under different physical environments. The environmental conditions studied were noise, cold, and immobilization.
The adult male rats were exposed to 100∼105 phone noise characterized by wide octave band spectrum for 3 hours, or to cold (-10±1°C) for 3 hours, or were immobilized for 2 hours. There-after, the animals were killed by two different methods; the one was decapitated at room temperature and the other was dropped into the mixture of solid carbon dioxide and acetone. The brain and liver were rapidly removed, and homogenized in ice-cold 10% trichloroacetic acid with glass homogenizers. The blood samples were obtained by heart puncture. The determination of ammonia was made by Conway's method using Seligson-Hirahata's apparatus.
As the results, under the noise condition, the ammonia content was elevated significantly in the brain, liver, and blood, but not under the other conditions.
It may be concluded that the noise acts not as metabolic stimuli but as neurotropic stimuli with a peculiar nature.