Fig. 1.

Immunohistochemical identification and firing patterns of respiratory interneurons recorded from C3–C5 ventral horn. A1–A3: one expiratory interneuron (light blue arrow; see B1 for firing pattern) and one inspiratory interneuron with tonic extended expiratory activity (red arrow; see C2 for firing pattern) double-labeled with neurobiotin (subpanel A1) and FITC-immunofluorescence secondary anti-GAD65/67 antibodies (subpanels A2 and A3). Scale bars: A1, 100 μm; A2 and A3, 60 μm. B1, B2, C1, C2: examples of recorded expiratory (top) and inspiratory interneurons (bottom) with extended expiratory activity. Averaged phrenic triggered integrated phrenic nerve activity (blue traces, arbitrary units, 100–120 sweeps, integration τ = 50 ms), cycle-triggered histograms (CTHs, red traces, 50–75 ms bin size) of analyzed interneurons (left scale, Hz), integrated phrenic nerve (PN) and spiking activity of recorded interneurons (low two black traces) are shown. Time bar = 250 ms, applied to B1–C2.