ABSTRACT
Some 50 years ago, Leusen, in his ventriculocisternal perfusion experiments in dogs, showed that variations in hydrogen ion concentration in the cerebrospinal fluid (CSF) had a pronounced influence on pulmonary ventilation [1]. These pioneer experiments were followed by the studies of Pappenheimer and co-workers in goats in which they showed that ventilation could be expressed as a unique function of a calculated extracellular pH existing at a location about three-fourths along the artificial steady-state concentration gradient of bicarbonate between the CSF and brain capillary plasma [2,3]. Following these classical studies, this view of central CO2 chemoreceptors that are uniquely sensitive to the pH in their microenvironment was also used by other groups in their attempts to define the ‘functional’ or ‘anatomical’ location of the central chemoreceptors (i.e., their relative distance between CSF and blood and their distance from the irregularly folded ventral surface of the medulla oblongata, respectively, e.g., [4-6]).
