REORGANIZATION OF PONTINE RHYTHMOGENIC NEURONAL NETWORKS IN KROX-20 KNOCKOUT MICE

We have shown previously that the inactivation of the zinc finger gene Krox-20 affects hindbrain segmentation, resulting in the elimination of rhombomeres 3 and 5. We demonstrate here that Krox-20 homozygous mu tant mice exhibit abnormally slow respiratory and jaw opening rhythms, indicating that a modification of hindbrain segmentation influences t he function of neuronal networks after birth. Central neuronal network s that control respiratory frequency are made predominantly depressant by the elimination of a previously undescribed rhythm-promoting syste m. Recordings of rhythmic activity from the isolated hindbrain followi ng progressive tissue transections indicate that the reorganization ta kes place in the caudal pontine reticular formation. The newborn (P0) Krox-20(-/-) mice, in which apneas are ten times longer than in wild-t ype animals, may be a valuable model for the study of life-threatening apneas during early infancy.