Stress state caused by alteration of rhythm in environmental temperature, and the functional disorders in mice and rats

Exactly how the organic mechanism corresponds to variations of environmental temperature has not been clarified and for elucidation we reared mice and rats under the conditions of alterating rhythm in temperature (ART). Mice (or rats) were reared at a temperature of 24°C and 8°C (or -3°C) every hour continuously from 10 a. m. to 5 p. m. and at 8°C (or -3°C) from 5 p. m. to the following 10 a. m.. Severe stress was evidenced in the animals and was termed specific ART-stress (SART-stress). In this type of stress, there was no apparent increase in body weight, respiration and heart rate were increased slightly and the QRS-time on the ECG was prolonged. ACh sensitivity of the isolated duodenum tested by the Magnus method in SART-stress mice was found to have declined considerably as compared to the normal. Histological observation of the SART-stress rats revealed that the wet weight of the spleen was lighter than that of the controls, while that of the lungs, heart, liver, stomach, kidneys and adrenal glands was close to that of control. Macroscopically, red brown spots on the lungs were visible. Ventricular hypertrophy, slight erosion and hyperemia were present in the interior of the stomach. On the galvanic skin response (GSR) test, electrical resistance of the skin of SART-stress rats was less than that of normal rats and the rate of increase of resistance caused by external stimulus was greater. Recovery time from change in GSR was shorter than in normal animals. Consequently, SART-stress appears to be a form of disease and sudden changes in temperature even in humans may contribute to this state.