ROLE OF CAROTID CHEMORECEPTORS IN THE INITIATION OF EFFECTIVE BREATHING OF THE LAMB AT TERM

Abstract

Respiratory patterns after deliberate cord occlusion of four fetal lambs with bilaterally divided carotid sinus nerves were compared with those of four control lambs subjected to similar surgery without actual division of the nerves. The animals with divided carotid sinus nerves did not develop sustained rhythmic respiration and showed fall in Po2, which persisted, and progressive fall in pH and rise in Pco2 during the 10-minute period of observation after cord occlusion. The mock-operated animals developed sustained rhythmic respirations and showed rise in Po2, fall in Pco2 and less fall in pH than the animals with divided carotid sinus nerves. This striking inability of the lambs deprived of carotid chemoreceptor function to initiate effective respiration indicates that this mechanism has an important role in the initiation of breathing under these conditions.