Fig. 3.
Effect of inspired isoflurane concentration on noxious-evoked activity in the primary somatosensory cortex at postnatal day 7. (A) Typical recordings of right somatosensory-evoked potentials after electrical stimulation of the left hind paw (10 × 3.2 mA, 500 μs stimuli applied at the time indicated by the dotted line) during increasing inspired isoflurane (Iso) concentrations. Grand average evoked potentials (filled lines) ±SEM (gray area) from 10 stimuli per animal (n = 7 animals). (B) Bar chart showing the peak evoked potential amplitude at each Iso step, normalized to initial recordings during 1.5% Iso (repeated measures [RM] ANOVA F(4, 24) = 78, P < 0.0001; Dunnett post hoc test, ***P < 0.001, compared with activity during inspired 1.5% Iso). (C) Time–frequency decomposition of the evoked somatosensory cortical neural activity shown in A. The time–frequency energy changes, time locked to each stimulus, are presented as a group median. Results are displayed as increases and decreases in energy relative to a baseline period of 1 s before stimulation. Energy values between 0 and −2 correspond to energy decreases, whereas values between 0 and 2 correspond to energy increases. n = 7 animals for each age group. (D) Evoked potentials as in A, but 10 min after plantar skin incision, (10 stimuli per animal in n = 6 animals). (E) Bar chart showing the peak evoked potential amplitude after hind paw incision at steps of increasing of inspired Iso concentration, normalized to recordings during 1.5% Iso (RM ANOVA F(4, 20) = 24, P < 0.0001; Dunnett post hoc test, **P < 0.01, compared with activity recorded during 1.5% Iso. (F) Time–frequency decomposition of the evoked somatosensory cortical neural activity shown in D, 10 min after plantar skin incision.