EFFECTS OF INHALATION ANAESTHETICS ON CAROTID BODY CHEMORCEPTOR ACTIVITY

In cats anaesthetized with pentobarbitone, the left carotid sinus was denervated by dissection of baroreceptor elements, and the mean integrated carotid body chemoreceptor discharge was recorded. Chemoreceptor response curves to altered Pao2 at constant end-tidal Pco2, and to altered Paco2 at constant Pao2, were plotted before and during pulmonary ventilation with diethyl ether, cyclopropane, or halothane. The response curves were tilted in the direction of chemoreceptor stimulation by cyclopropane and by ether, while halothane appeared to depress the discharge. In no instance did the inhalation anaesthetics increase chemoreceptor activity above the maximum attainable by blood gas changes alone. Reductions in arterial pressure caused by the anaesthetics influenced these results, increased chemoreceptor activity, and could overcome the effects of blood gas changes.