Some characteristics of temperature regulation in the unanesthetized dog

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Abstract
An attempt was made to ascribe the regulation of body temperature in homeo-therms to the hypothalamus and the preoptic region. Results of measurements of hypothalamic temperature and regulatory responses in the normal dog in hot, neutral, and cold environments and in the resting, waking state are interpreted on the assumption that the hypothalamus responds to changes in its own temperature like a proportional controller with an adjustable set point. The controlling equations relating panting and shivering responses to the activating signal were of the form R[long dash]Ro = [alpha]r(THypo [long dash]TSetR,). R[long dash]Ro [greater than or equal to] o. For a11 environmental temperatures, the proportionality constant for the shivering response was between -1 and -1.5 kcal kg-1 hr.-1 [degree]C-1. The proportionality constant for panting was 2-3 kcal kg-l hr.-l [degree]C-1 and was the same for all environmental temperatures. The set temperature for all regulatory responses increases in the cold environment and decreases in the hot environment. The set temperature for panting exceeds the set temperature for shivering by about 2 C in cold environment (avg skin temp., TAS ; 33 C), 2-3 C in neutral environment (TAS = 35 C) and possibly 4 C in hot environment (TAS = 37 C). The set temperature for vasocon-striction is between that for shivering and panting. A high internal body temperature lowers all set temperatures and a low internal body temperature increases all set temperatures without affecting the proportionality constants.