Abstract-In order to explore the peripheral microcirculation and to obtain an outline of autonomic innervation in SARI (specific alternation of rhythm in temper ature)-stressed (repeated cold-stressed) animals, which are regarded as model animals for clinical vagotonic-type dysautonomia, peripheral tissue blood flow was determined in mice, using the hydrogen clearance method.SART-stressed mice showed a decrease in gastric blood flow, no change in hepatic blood flow and an increase in dermal blood flow. In the mice exposed to the restraint and water immersion stress (RWIS), a type of acute stress, in contrast with SARI stress which is a subacute type, remarkable decreases were observed in gastric, hepatic and dermal blood flows.Changes of both gastric and dermal blood flow in SART stressed mice were dose-dependently prevented and maintained within normal limits by the treatment with Neurotropin, a sedative analgesic which is an extract isolated from vaccinia virus-inoculated and inflamed skin of rabbits. In RWIS loaded mice, Neurotropin exhibited a great preventive effect on changes of blood flow in the stomach, a slight effect in the liver, and no effect in the cutis. When mice were loaded with SARI stress after left-cervical vagotomy, SARI stress failed to elicit any decrease in gastric blood flow. In SARI-stressed mice treated with 6 hydroxydopamine, gastric and dermal blood flows tended to show a further decrease and increase, respectively, over and above the changes caused by SART stress. From these results, it is suggested that SART-stressed mice may have decreased gastric parasympathetic tone, a decrease in sympathetic tone and also other anomalies such as increased tension of the sympathetic cholinergic vasodilator nerves in the cutis.There have been numerous reports that SART (specific alternation of rhythm in temperature) -stressed (repeated cold stressed) animals (1, 2), vagotonic-type model animals (3) for clinical autonomic imbalance, show various physiological changes (3-7). With respect to the circu latory system of SART-stressed animals, several abnormalities (5,6,8,9) such as a continuous lowering of blood pressure (5), sympathicotonic-type ECG (electrocardio gram) (6), increases in blood flow in the abdominal aorta and superior mesenteric artery, and decreased blood flow in the common carotid artery (5), have been previously reported.