Figure 1.

Chronic nicotine induces persistent changes in EPSP–Spike coupling. A, Examples of orthodromically evoked EPSPs and action potentials recorded intracellularly from CA1 pyramidal cells in current-clamp with matching EPSP slopes recorded from slices from 4 week withdrawn animals. The nic-cell (blue) has a firing probability of 0.5, while the sal-cell (red) is subthreshold for action potential firing. Stimulus artifact has been removed for clarity, and a black triangle represents time of stimulus. B, C, Mean intracellular E-S curves from 1 d withdrawn (B) (sal-cells, n = 7; nic-cells, n = 5) and long-term (4-week + 3-month) withdrawn (C) (sal-cells, n = 4; nic-cells, n = 7) animals. D, Examples of orthodromically evoked suprathreshold fEPSPs recorded in stratum radiatum (top traces) and pSpikes recorded in stratum pyramidale (bottom traces) from 1 d withdrawn animals (sal-slice: red; nic-slice: blue). For a given fEPSP slope, nic-slices have an increased pSpike amplitude. Stimulus artifacts have been removed for clarity, and black triangles represent time of stimulus. E, Mean extracellular E-S curves from 1 d withdrawn animals (sal-slices, n = 37; nic-slices, n = 36). F, Histogram showing the maximal pSpike amplitude for different periods of withdrawal: 4 week (sal-slices, n = 12; nic-slices, n = 20); 3 month (sal-slices, n = 17; nic-slices, n = 22); 6 month (sal-slices, n = 6; nic-slices, n = 10); and 9 month (sal-slices, n = 4; nic-slices, n = 5). G, Examples of aSpikes recorded in stratum pyramidale from 1 d (top) and 9 month (bottom) withdrawn animals (sal-slices: red; nic-slices: blue). Stimulus artifacts have been removed for clarity and black triangles represent time of stimulus. H, I, Mean aSpike I-O curves from 1 d withdrawn (H) (sal-slices, n = 20; nic-slices, n = 18) and 9 month withdrawn (I) (sal-slices, n = 4; nic-slices, n = 5) animals. Data are presented as the mean ± SEM. S. Rad., Stratum radiatum; S. Pyr., stratum pyramidale. *p < 0.05.