Comparative biochemical responses of rats to different stressful stimuli.

Adult male rats were exposed to single applications of one of three stressful stimuli (low environmental temperature, immobilization, random footshock) for periods up to 4 hours and plasma levels of corticosterone (PCS), fatty acids (PFA), and glucose (PGL) were determined at various points during the stress exposure and 1 and 2 hours post-exposure. The levels of PCS were increased by all 3 stressful stimuli in a similar temporal pattern, with the greatest magnitude of effect seen for immobilization and the least for cold exposure. The time courses of increased PFA levels were similar for immobilization and cold exposure; the response to foot shock was delayed in onset by 2 hours. The PGL response was minimal for cold exposure and foot shock, but showed a marked elevation during the first 2 hours of immobilization. The results suggest that the response pattern obtained is characteristic of the stressful stimulus employed, with PCS showing the least degree of specificity.