Effects of potassium and lactic acid on chemoreceptor discharge in anaesthetized cats

Both increasing [K+]a and falling pHa stimulate ventilation through an action on the peripheral chemoreceptors. We have examined the effect on afferent carotid chemoreceptor discharge, of intravenous infusion of lactic acid alone, KCl alone, and both combined at constant PETCO2 in anaesthetized, artificially ventilated cats. Infusions of lactic acid alone and KCl alone caused similar increases in both the mean and amplitude of oscillation of chemoreceptor discharge. In the case of the lactic acid alone infusion the increase in the amplitude of oscillation could be accounted for by the resultant increase in carbon dioxide production. Simultaneous infusion of KCl and lactic acid caused an increase in the mean and amplitude of the discharge which was greater than either given alone, although the combined effect was less than additive. The alterations in mean and amplitude of oscillation of discharge during infusion of both agents together may be completely accounted for by a combined effect of increased carbon dioxide production and elevated [K+]a.