Electrophysiological investigation of cells in the region of the anterior hypothalamus firing in relation to blood pressure and volaemic changes.

The anterior hypothalamus has been implicated in the higher centre control of blood pressure and more recently in hydromineral balance regulation. Using a glass recording electrode with and without a 7-barrelled iontophoretic electrode we investigated this region for blood pressure-sensitive cells. We used a ventral approach through the optic chiasma. We found 36 cells out of 91 tested that increased their firing rate in response to a spontaneous or induced decrease in blood pressure. Of these 19 increased firing in response to angiotensin II (AII) injected into the lateral cerebral ventricle and 10 of these increased firing in response to local iontophoretic application of AII. Cells responsive to an increase in blood pressure were never found. Thus cells in this area respond to hypovolaemia and hypotension as well as to AII, which could link this area with higher centre responsiveness to stimuli of extracellular thirst.