Abstract
Urinary nitrogen level of rats was determined before, during, and after the first stress (avoidance conditioning) and the second stress (extinction) period for 60 days. The level increased rapidly with stress and reached maximum during the first stress which coincided with an anxiety behavior. And the level was kept during the second stress. It restored and decreased rapidly after the stress. The excretion per intake ratio increased rapidly reaching maximum during the first stress period in all animals. And gradually decreased during and after the second stress period. The increased excretion ratio indicates an increase in protein catabolism. Increased selection of protein induced by the emotional stress is assumed to be closely related to the increased protein metabolism.
