Interaction of respiratory cell discharge patterns and spontaneous resporatory rate

Potentials from single respiratory cells in the inspiratory and expiratory populations of the medulla were recorded by extracellular microelectrodes in spontaneously breathing cats anesthetized with pentobarbital. Experiments were designed to follow alterations in single-cell discharge patterns after modification of the respiratory rate by either barbiturate depression or doxapram activation. Unit activity was quantitated by a computerized mathematical technique based on the sequential arrangement of interspike intervls. From this analysis several discharge parameters were derived which successfully quantitated initial (frequency increase), middle (frequency plateau), and terminal (frequency decrease) phases of spike activity. Discharge parameters were correlated with respiratory rate by the use of linear and curvilinear regression analyses. Theoretical discharge patterns for both inspiratory and expiratory populations were reconstructed at selected respiratory rates by interpolation from regression equations. These data, demonstrating average quantitative shifts in cell activation and deactivation phases as a function of respiratory rate, suggested several possibilities for the modulation of the respiratory frequency.