Figure 4. Evidence for more complex inhibitory inputs.

Two internal intercostal nerve motoneurones are illustrated. A, decerebrate following halothane: a CRDP defined as biphasic inhibitory: note the small hyperpolarizing potentials that precede the larger (2 mV) hyperpolarizations in inspiration. The former occur simultaneously with the EBSN discharge (top 2 traces) and the expiratory discharge in the T6 external nerve discharge (3rd trace). Note absence of all 3 in the second respiratory cycle. B, ketamine anaesthetized: a CRDP that was defined as expiratory. When initially recorded at a membrane potential of −42 mV, it showed a depolarizing ramp of amplitude 1.5 mV during expiration. Note that the synaptic noise increases in both respiratory cycles as expiration progresses. C, extract from B (at the time of the arrow) shown on an expanded time scale, illustrating that this noise is dominated by IPSP-like waveforms.