EFFECTS OF INHALATION OF 100 PER CENT AND 14 PER CENT OXYGEN UPON RESPIRATION OF UNANESTHETIZED DOGS BEFORE AND AFTER CHEMORECEPTOR DENERVATION

Abstract

Expts. were performed upon unanesthetized dogs before and after denervation of the carotid and aortic bodies to obtain information concerning (a) tonic activity of the chemoreceptors under normal conditions and (b) direct effects of anoxia upon the respiratory center. Evidence was obtained that at least some chemoreceptors are normally-active in unanesthetized dogs breathing room air at sea level for inhalation of 100% O2 for 6 mins. in 7 dogs led to transient diminution in respiratory minute vol. ( [long dash] 11[long dash]- 31%); some chemoreceptors must have been continually-activated by the small degree of O2 unsaturation in arterial blood for similar depression did not occur after chemo-receptor denervation. Anoxia (14% O2) increased respiratory minute vol. 17-29% in unanesthetized intact dogs, but in the denervated dogs anoxia diminished minute vol. 22-29% for the 1st 4 mins. Following this there was a return to normal due to rate acceleration despite continued anoxia. The possible causes of this delayed acceleration are discussed.