Changes in Electrical Activity of the Medulla on the Intravenous Injection of Hypertonic Solutions

¹ From the Department of Anatomy, School of Medicine, University of California, Los Angeles and Veterans Administration Center, Los Angeles, California

Electric recording with insulated steel electrodes in the dorsal part of the medulla of the cat has revealed an area which responds to changes in the tonicity of the blood stream. Hypertonic saline solutions injected intravenously resulted in a response characterized by increased electrical activity in the floor of the fourth ventricle at the level of the obex. The region involved is in juxtaposition to the area postrema overlying the vagal nuclei and may represent a central site of osmoreception.