Fig. 6

Gap-junction blockers disrupt fictive respiration in the intact network and attenuate or silence syncytial oscillations. A.i Syncytial activity recorded rostrally (blue) and caudally (orange) reveals rapid attenuation of oscillation amplitude following application of 100 μM gap-junction blocker meclofenamic acid (MFA) under synaptic blockade; points in the upper trace mark the peaks used to quantify amplitudes. A.ii MFA significantly reduces oscillation amplitude (paired t-test, p = 0.02). A.iii Cartoon indicating the field of view of rostral and caudal 20X recordings of syncytial activity. B.i In the intact network, bath application of 100 μM MFA rapidly silences respiratory motor output (top trace) and network activity (not shown). B.ii At 80 μM, MFA slows motor output (top trace), as well as network activity (lower traces), but no neurons active in the intact network fall silent nor are ectopic bursts over subnetworks detected. B.iii Poincaré plot of periods from the dataset shown in B.i do not display discrete clusters, as would be expected if drive to (pre)motoneurons was disrupted, leading to periods at integer multiples of control [26]. B.iv Histogram of post-MFA wash-in periods divided by control periods (N = 7) forms a skewed unimodal distribution. If MFA disrupted transmission of rhythmic drive to (pre-)motoneurons, we would expect to see multiple peaks; their absence suggests that gap junctions play a role in stabilizing respiratory period. B.v Averaged burst amplitude for 1 cycle before (green arrow in B.ii, green trace) and during MFA wash-in (purple arrow in B.ii, purple trace) reveals that neither inspiratory burst amplitude nor onset were attenuated by MFA. C Application of the broad-spectrum gap-junction blocker carbenoxolone (CBX, 100 μM; N = 6) transiently increased syncytial amplitude (10 min, gray line) compared to baseline (red line); thereafter, frequency slowed, and amplitude was attenuated (20 min, fine black line), and after 30 min, it was undetectable (30 min, thick black line)