Figure 5. Anoxia effects on cervical and lumbar respiratory rhythms in brainstem-complete cords.

The upper 3 traces show simultaneous recordings from the left cervical (lC₃) plus the left and right 1st lumbar (lL₁, rL₁) ventral nerve roots, whereas the lower 3 columns of traces illustrate parts of the continuous recording at higher time resolution. In control solution, inspiratory cervical nerve activity was accompanied by 1 : 1-coupled pre/postinspiratory lumbar nerve bursts. Chemical anoxia induced an identical reduction of the frequency of cervical and lumbar nerve bursting and evoked cervical double bursts (asterisks) after ∼10 min. Anoxia had no major effect on the amplitude of cervical bursting, but progressively augmented lumbar activity with a concomitant pattern transformation from pre/postinspiratory to inspiratory/postinspiratory. The progressive anoxic potentiation of lumbar bursting continued after the onset of inspiratory cervical double bursts. Note the short duration of the lumbar burst that appeared simultaneously with the first of the cervical double burst.