Figure 2.

Quantal pattern of breathing in an 8-day-old vagotomized rat given fentanyl

A, intervals between successive EMG_ABD bursts (circles) and inspirations (squares) for 220 consecutive respiratory cycles: 120 I-E cycles (mean duration of I-E cycles ) and 100 E-only cycles (mean duration of E-only cycles ). B, recording of epoch shown in A (∼(150 s, 190 s); green squares represent normal, i.e. I-E cycles (1, 3, 6, 8, 9), and red circles represent E-only cycles (2, 4, 5, 7). Traces from top to bottom: cycle number, EMG_GG, EMG_ABD, their integrals (∫EMG_GG and ∫EMG_ABD), V_T and respiratory flow. Vertical dotted lines mark the onset of each EMG_ABD burst. E-only cycles differed from I-E cycles; see C, D and text. C, ∫EMG_GG and ∫EMG_ABD on an expanded time scale to show pattern of bursting in an I-E cycle (cycle 1); note that ∫EMG_GG has two distinct components (I-EMG_GG and E-EMG_GG) and can have no delay between them or be separate, e.g. Fig. 3, paired vertical lines. EMG_ABD activity has a two-burst structure. D, comparison of an I-E cycle (cycle 1) and an E-only cycle (cycle 2, red).