Mean changes in cortical and VTA EEG and EMG total powers induced by intravenous nicotine, nicotinePM, and saline in drug-naive conditions and after drug experiencea
| Group | Immediate effect (5–30 s) | Long-term effect (30–300 s) | ||||
|---|---|---|---|---|---|---|
| Cortex | VTA | EMG | Cortex | VTA | EMG | |
| Nicotine (naive) | 32.47 ± 2.99 | 26.23 ± 2.11 | 8.38 ± 0.30 | 36.00 ± 2.50 | 27.43 ± 2.13 | 8.11 ± 0.34 |
| Nicotine (Nicotine) | 30.39 ± 2.25 | 24.51 ± 1.99 | 7.90 ± 0.27 | 29.85 ± 1.66* | 23.00 ± 1.76 | 7.65 ± 0.33 |
| NicotinePM (naive) | 38.85 ± 2.28 | 31.06 ± 4.23 | 6.58 ± 0.11 | 74.94 ± 3.14 | 68.02 ± 5.12 | 4.94 ± 0.51 |
| NicotinePM (NicotinePM) | 63.48 ± 3.86*** | 51.96 ± 5.08*** | 5.87 ± 0.09*** | 93.25 ± 4.42*** | 84.43 ± 4.25* | 4.15 ± 0.37 |
| NicotinePM (Nicotine) | 36.04 ± 1.43†† | 32.71 ± 2.04†† | 7.11 ± 0.19†† | 59.06 ± 6.38*,†† | 48.90 ± 4.98*,†† | 6.99 ± 0.49*,††† |
| Saline (naive) | 53.68 ± 3.14 | 46.16 ± 4.17 | 5.68 ± 0.25 | 87.63 ± 3.18 | 80.10 ± 3.52 | 4.64 ± 0.25 |
| Saline (NIC) | 41.99 ± 5.00 | 35.25 ± 4.12 | 6.73 ± 0.28* | 80.73 ± 4.14 | 72.17 ± 4.09 | 4.71 ± 0.26 |
↵aData are grouped depending upon the drug tested (nicotine, nicotinePM, or saline) and previous drug experience: (naive), No experience, (Nicotine) and (NicotinePM), 2 d of previous nicotine or nicotinePM treatment, respectively. EEG total power is represented in percentages versus preinjection baseline (100%). Because of large-magnitude changes, EMG total power is shown as ln(%).
↵Significant differences in each drug group (saline, nicotine, and nicotinePM) versus “naive” conditions (*p < 0.05; ***p < 0.001; Student's t test). Significant differences between the effects of nicotinePM after previous nicotinePM and nicotine experience (†p < 0.05; ††p < 0.01; †††p < 0.001).