Fig. 2.

Effect of water deprivation on respiratory rhythmic sSNA. A: PNA burst-triggered averages of sSNA from a euhydrated control (left) and 48-h WD (right) rat. The timing of neural inspiration is indicated by PNA bursts (shaded dashed lines). B: features of respiratory modulated sSNA are shown in the top left. Examples in A show a prominent IP of sSNA occurred in the control and WD rat. Note that the amplitude was greater in the control than the WD rat. The IP was followed by an early expiratory (postinspiratory) trough (ET) and a small late expiratory peak (EP). Summary data (n = 8/group) in the top right reveal that the mean voltage of sSNA was significantly greater in WD rats (solid bar) compared with controls (open bar), whereas IP amplitude (bottom left) was significantly smaller in WD than control rats. Amplitudes of the early ET and late EP when present in control rats (see text for details) were similar across groups. Bottom right: rhythmicity index values. Note that respiratory modulation of sSNA across the entire respiratory cycle (Total) was significantly less in WD rats compared with controls. The IP was the major contributor to total respiratory modulation in control rats, but its role was significantly less in WD rats. Contributions of the early ET and late EP to overall respiratory modulation were similar across groups, with the late EP playing a minor role in overall respiratory modulation in both groups. Triggered averages of sSNA were constructed from 150 consecutive PNA bursts. Summary data are means ± SE. *P < 0.05 vs. control. †P < 0.0005 vs. control. Δ, Change.