RESPIRATORY AND VASOMOTOR EFFECTS OF VARIATIONS IN CAROTID BODY TEMPERATURE

Abstract

The carotid body zones of dogs, vascularly isolated from the carotid sinus pressoreceptors and all other regions, were perfused under constant hydraulic conditions with normally aerated blood at temps. varying within the limits of 15[degree]C. and 45[degree]C. Increased temp. caused reflexly increased breathing and reflex vasoconstriction, which are indications of increased chemoceptor activity. Conversely, decreased temp. caused reflexly diminished breathing and reflex vasodilatation, which are indications of lessened chemoceptor activity. These findings demonstrate a further correspondence between changes in chemoceptor activity and theoretically concurrent changes in chemoceptor acidity and they are therefore considered to support the hypothesis that the functional activity of chemoceptors is dependent upon the rate and quality of their own acid metabolism as well as upon the properties of their environment. Cold perfusion as performed in these expts. constitutes selective inactivation of the chemoceptors alone. Since such chemoceptor inactivation caused reduced breathing up to 34% of the normal, it is concluded that, in anesthetized animals, the carotid chemoceptors exert a tonic stimulating effect of significant proportions upon the respiratory center.