Effect of Change in Air Temperature Upon Systemic Small and Large Vessel Resistance

Direct resistance measurements in the foreleg of the anesthetized dog show that the rise in total resistance following reduction of air temperature is due predominately to small vessel constriction and is based upon at least three different mechanisms. The large arteries and veins also constrict and evidence is presented which suggests that the venous and possibly the arterial resistance responses are predominately due to changing levels of circulating epinephrine, norepinephrine or both.