Effect of carotid chemoreceptor denervation on breathing in utero and after birth.

The influence of the carotid bodies on fetal breathing activity in utero and on the establishment of postnatal breathing was studied. The electrocorticogram, the electromyogram of the lateral rectus and postural muscles, and tracheal and arterial pressures were monitored on chronically prepared intact and carotid sinus-denervated fetal lambs. The denervated fetuses required a longer time for recovery from the operation, but thereafter the sleeping and breathing behavior was similar to that of the control group. Four of the carotid sinus-denervated fetuses were allowed to be delivered spontaneously, and all established regular postnatal respiration despite conclusive evidence of nonfunctional carotid bodies. These experiments indicate that the fetal carotid chemoreceptors are not essential for the spontaneous intrauterine breathing activity during rapid-eye-movement sleep nor for the establishment of effective breathing at birth.