The respiratory and circulatory systems of the body can be stimulated when carbon dioxide and hydrogen ions activate certain brain cells (neurons). These neruons are considered to be chemosensitive and, based on earlier studies, were thought to be localized exclusively along one surface of the brainstem, i.e., the ventrolateral medulla oblongata. Recent evidence, however, now suggests that chemosensitive neurons have a wider distribution than previously believed and that they are also located in a region called the nucleus of the solitary tract. Both of these regions will be studied. Chemosensitive neurons are thought to provide tonic input to both the cells that generate breathing rhythm and the cells that control vascular tone. Chemosensitive cells also maintain the acid-base balance during periods of metabolic disturbance and changes in the external environment. Despite the importance conferred on these neurons, the exact neural pathways and cellular mechanisms by which they produce their effects are not known. In the proposed studies, electrophysiological recordings will be made from these neurons and their responses to changes in oxygen level, acid-base balance and drug application will be studied. The cells will be localized and the way in which they are connected to other parts of the brain will be investigated. This work will contribute to fundamental knowledge of how the brain controls the respiratory and circulatory systems of the body.
