Fig. 4. ( A ) Individual example showing the effects of isoflurane (ISO) on ventral root power spectra in the rostral ( dotted line ), middle ( solid black line ), and caudal ( gray line ) compartments. Isoflurane progressively decreased peak spectral amplitude in the rostral and caudal compartments. During 1.5% isoflurane ( lower left spectra ), activity in the middle compartment that received isoflurane was virtually abolished, while the caudal rhythm shifted to a lower frequency. ( B ) Mean data showing effects of isoflurane on peak spectral amplitude. Isoflurane significantly reduced spectral amplitudes in the rostral ( open bars ) and middle ( solid bars ) compartments at all isoflurane concentrations, and in the caudal compartment ( shaded bars ) at 1.0% and 1.5% isoflurane. ( C ) Mean isoflurane effects on the frequency of the locomotor rhythm. Isoflurane significantly reduced the mean burst frequency in the middle and caudal compartments at a concentration of 1.5%. * Significantly decreased from baseline (BL) values.