Hypothalamic Unit Response to Increases in Arterial Blood Pressure. ∗

Summary

The responses of hypothalamic unit activity to changes in arterial blood pressure were studied in 14 cats under nembutal anesthesia. Areas of the posterior hypothalamus were stimulated in order to determine the points from which maximal increases in blood pressure could be obtained. A tungsten recording electrode was placed at these points and a single unit activity recorded. Arterial blood pressure was increased by infusion of 2 μg/kg of adrenalin intra-arterially and by occlusion of the abdominal aorta. With infusion of adrenalin, there was an increase in the frequency of firing in 55% of the cells, whereas with occlusion of the aorta there was a decrease in 75%. A direct effect of adrenalin was not ruled out. These results were interpreted as resulting from two different populations of pressure-sensitive cells in the posterior hypothalamus.