Anoxia induced functional inactivation of neonatal respiratory neurones in vitro.

In the isolated brain stem-spinal cord preparation of neonatal rats, respiratory (C4) activity persisted at reduced frequency during tissue anoxia. In seven biphasic expiratory (Bi-E) and in 12 of 22 inspiratory (Insp) neurones, recorded with the 'blind' patch-clamp technique, anoxia evoked a persistent hyperpolarization by up to 16 mV whereas membrane potential of the remaining Insp neurones depolarized slightly or remained unaffected. Respiration-related synaptic potentials and action potential discharges were blocked in all Bi-E and in about 50% of the Insp neurones, whereas rhythmic activity persisted in the other cells. The results indicate that a major population of neonatal respiratory neurones is functionally inactivated during anoxia. This mechanism might contribute to the anoxia tolerance of the immature brain.