Acute modification of embryonic spinal cord activity induced by hypoxia.

The effects of acute environmental hypoxia on spinal cord polyneuronal activity throughout the later stages (14, 16 or 19 days) of chick incubation were studied. Bioelectrical activity was recorded in ovo from lumbosacral regions of the spinal cord, and frequency histograms were computed from multiunit (burst) activity during a 5-min control, an altered environment (10% O2) period, and a recovery period following hypoxic episodes. An hypoxic environment inhibited burst activity at 14 and 19 but not at 16 days. An age-dependent ability to recover from an acute hypoxic depression of neural activity was apparent, but multiple episodes of hypoxia depressed burst frequency to the same level independent of age. Hypoxia may inhibit the functional expression of specific neuron pools. The different responses to and recovery from hypoxia observed in this embryonic series may be dependent on the relative development of different components of the neuroaxis in the chick. Metabolic processes with age-related capabilities may also influence the different responses which were observed.