Fig. 8.
Effect of isoflurane and hind paw incision on noxious-evoked activity in primary somatosensory cortex at postnatal day (P) 30. (A) Typical recordings of P30 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 isoflurane step, normalized to initial recordings during 1.5% Iso (repeated measures [RM] ANOVA F(4, 24) = 49, P < 0.0001; Dunnett post hoc test, **P < 0.01, and ***P < 0.001, compared with peak evoked potential amplitude during 1.5% Iso). (C) P30 evoked potentials as in A, but 10 min after plantar skin incision (10 stimuli per animal in n = 6 animals). (D) Bar chart showing the peak evoked potential amplitude after hind paw incision at steps of increasing of inspired isoflurane concentration, normalized to recordings during 1.5% Iso (RM ANOVA F(4, 20) = 24, P < 0.0001; Dunnett post hoc test, *P < 0.05, **P < 0.01, ***P < 0.001, compared with activity recorded during 1.5% Iso. (E) 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. (F) Time–frequency decomposition of the evoked somatosensory cortical neural activity shown in C, 10 min after plantar skin incision.