Relationship between body temperature and autonomic nervous tone in spontaneously hypertensive rat (SHR).

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Core temperature and autonomic nervous tones were compared spontneously hypertensive rate (SHR,200 mmHg), stroke-prone SHR(SHRSP,250 mmHg) and Kyoto-Wistar rats (WKY,120-130mmHg). 1) Body temperature; Each rat was placed in a small wire-mesch cage for the loose restraint, rectal temperature(Tre) and tail skin temperature (Ttail) were recorded continuously. Tre was estimated in 30 min of 60th to 90th min from the beginning of the restraint. Mean Tre in SHR,SHESP and WKY of 6-9 Months old were 38.7 0.3゜C,38.3 0.3 c and 37.7 0.1 C,respectively. Tre were in the oder SHR>SHRSP>WKY,though blood pressure were in the oder SHRSP>SHR-WKYW. 2) Threshold core temperature; during a gradual rising of air temperature at constant rate of 0.2゜C/min, stepwise increses in Ttail were observed which indicate the tail vasodilation. Threshold core temperature for the tail vasodilation in SHR,SHRSP and WKY were 38.9 0.1゜C,38.9 0.1゜C and 38.4 0.1゜C,respectively. Threshold core temperature in SHR was higher than those in other two strains and it in the SHRSP was lower than SHR. 3) Autonomic nervous tone ; Cardiac autonomic nervous tones were estimated by the pharmacological method (Lin and Horvath, 1972). In male rats of 6-7 months old, parasympathetic tones were 19.4%,15.9 % and 15.2%, sympathetic tones were 38.3%,24.0% and 29.6%, respectively. Both sympathetic and parasympathetic tones in SHR were highest among the three strains. 4) Effect of the restraint; Initial Tre in SHR,SHRSP and WKY (5-7M) were 38.4 0.1゜C,38.5 0.2゜C and 37.8 0.2 c,respectively. When the rat was placed in the restrain cage, Tre and heart rate incresed but ttail sudtainly decreased. At the biginning of the restraint, Tre gegan to increase and declined gradually toword the initial level. Maximal values of the Tre were observed between 10th to 30th min after beginning of the restraint. An upper shift of Tre by the restraint in SHR was larger than those in others, and these upper shift of Tre decreased with age.