Figure 3. GABA_A receptor blockade alters burst amplitude, frequency, and pattern.

A, traces of integrated hypoglossal respiratory motor output are shown with increasing bicuculline concentrations (0-50 μM). B-E, group data from 11 brainstems are shown with the same symbols as in Fig. 2. B, bicuculline tended to increase amplitude at 10 μM, and significantly increased amplitude by > 200 % at 50 μM. C, frequency was significantly increased at 10 and 50 μM by 4–8 bursts (10 min)⁻¹. D, burst duration was unaltered at all bicuculline concentrations, but there was a dose-dependent decrease in peak time (P < 0.05 at 10 and 50 μM), reflecting a shift to a rapid onset-decrementing pattern. E, all bicuculline effects were reversible following washout (n= 4).