Arterial blood pressure and electric activity of aortic nerves in rabbits during hyperthermia

The experiments were carried out on 30 rabbits with whole body heating to lethal temperatures. During the process of heating records were done of the rectal temperature, arterial blood pressure, heart rate, ECG and action potentials in the aortic nerves. It was found that heating the animals up to 41.5 degrees and to 43 degrees C increased initially slightly the arterial blood pressure but then decreased this pressure gradually. The heart rate increased during heating but decreased steeply at temperatures preceding death. The fall of the arterial blood pressure was associated with a decrease in the frequency of action potentials in the aortic nerves. The appearance of isolated action potentials within several minutes after heart arrest suggests spontaneous activity of certain baroreceptors.