Age-related electrocorticographic and respiratory adaptation to repeated hypoxia

Severe hypoxia is known to produce depression in electrical brain activity and perturbation of respiratory pattern. In piglets undergoing chronic recording of brain and respiratory muscle activities, a depressed electrocorticogram (ECoG) was observed in response to rapidly induced (< 30 s), brief (10 min), and moderate hypoxia (10% O2 in 90% N2) in 16 out of 42 study sessions in young (3- to 11-day-old) animals only. Responses to hypoxia were monitored over 4 consecutive days. In five cases, the latency to the onset of the ECoG depression increased progressively over the 4 test days, and its duration decreased progressively. An associated respiratory gasping pattern also exhibited gradual remission over consecutive days. These changes in the responses to repeated hypoxia demonstrate adaptation of mechanisms underlying neuronal perturbation by oxygen deprivation.