EFFECTS OF HYPOXIA ON PHRENIC NEUROGRAM RESPONSE TO VAGAL AND SOMATICSTIMULATION IN NEWBORN RABBITS

Effects of 10% O2 on the response of the phrenic neurogram to vagal (V S) and saphenous stimulation (SS) were studied in anesthetized and art ificially ventilated newborn (group 1: 1-3 days old, n = 13; group 2: 8-14 days old, n = 14) and adult (group 3, n = 12) rabbits. In all ani mals during ventilation with 100% O2 or 10% O2 in N2, VS caused a redu ction in the expiratory phase (Te). Te shortening in response to SS wa s unaffected by hypoxia in group 3, and was abolished in group 2. In g roup 1, only early hypoxia blocked the Te response to SS. The preserve d Te response to VS on one hand, and abolished the effects of SS on th e other, suggest that blockade of the somatic inputs is due to the age -dependent action of hypoxia in areas distant to the respiratory neuro ns.