Figure 2. Characteristics of the respiratory abdominal motor outflow in juvenile and neonatal rat in situ preparations.

Representative activity patterns of phrenic (PN), hypoglossal (HN), lumbar abdominal (AbN) and central vagus (cVN) nerves recorded simultaneously during eupnoea (5% CO₂) and hypercapnia (7%, 10% CO₂) in juvenile (A) and neonatal rats (B). Raw (grey traces) and integrated (black traces) motor nerve outputs; vertical dashed lines indicate onset of HN bursts. Hypercapnia (7% CO₂) elicited typical AbN late-E bursts (arrowheads) that exhibited cycle-to-cycle ‘skipping’ but were stable at 10% CO₂. Insets in A: late-E AbN bursts were correlated with shorter duration of the preceding cVN post-inspiratory activity (see also Fig. 3E). The time scale in the insets indicates time from the end of inspiration in PN.