Neonatal breathing control mediated via the central chemoreceptors

Respiratory changes elicited via the central chemoreceptor system have been studied in anesthetized newborn guinea pigs and newborn rabbits. Periodic breathing was induced by inhibition of the central chemoreceptors by superfusion with alkaline cerebrospinal fluid. The periodic breathing was promptly reversed to steady by increasing the oxygen or carbon dioxide concentration in the inspired air or by intravenous theophylline. Elicitation of periodic breathing simply by exposing the animals to hypoxia succeeded only when very low oxygen concentrations were given. Clearcut respiratory excitation was produced by small amounts of theophylline applied onto the ventral surface of the medulla. Not only theophylline intravenously but also theophylline topically applied on the ventral medullary surface normalized spontaneously developed periodic breathing. Application of meperidine onto the ventral medullary surface gave respiratory inhibition with dosages considerably lower than required when given intravenously. The results emphasize the importance of an adequate respiratory drive from the central chemoreceptors for the maintenance of a regular breathing pattern. The findings support a view that at least part of the respiratory effects seen in the newborn following administration of meperidine or theophylline is due to effect of the drugs on the central chemosensitive system.