Blood Pressure of the Woodchuck and its Response to Injections of Histamine and Epinephrine

Abstract

Opportunity was afforded recently of measuring the blood pressure of the woodchuck. Two fine male specimens weighing 1.7 and 2.5 kg. respectively were obtained for another purpose but before the animals were killed they were etherized. A cannula was inserted into the left femoral artery of each animal and the blood pressure recorded in the usual manner. The initial value for the blood pressure of the larger animal was about 135 mm. of mercury, while that of the smaller animal was about 90 mm. of mercury. As compared with the blood pressure of the rabbit that of the larger woodchuck was considerably higher but the blood pressure of the smaller animal was about equal to that of the rabbit.

Since it is well known that the blood pressure of a rabbit may be elevated or depressed by appropriate doses of histamine given intravenously, I was interested in determining the effect of this amine on the blood pressure of another rodent, such as the woodchuck. Doses of 0.1 mg. of histamine given intravenously to both woodchucks caused a marked fall in blood pressure. After the blood pressure had returned to the control level, another dose of the same size caused a comparable effect.

In response to an injection of 0.1 cc. of 1:1000 solution of epinephrine given intravenously, the value for the blood pressure of each of the woodchucks was raised to about 200 mm. of mercury. There was considerable fluctuation below and above the control level but the blood pressure became stabilized within 4 minutes. At the completion of these observations, the animals were killed (Fig. 1).