Figure 8.

Nicotine modifies locomotor sensitization and corticostriatal activity. A, Protocol for testing the effect of amphetamine and nicotine on locomotor sensitization. The amphetamine treatment group received saline injections for the first 2 d, whereas the saline treatment group received saline on all days. B, Average locomotor ambulations over 90 min in mice treated with either saline or amphetamine. C, Interval locomotor ambulations over 90 min; compare the ambulations following the first injection of amphetamine with those following an amphetamine challenge in withdrawal. Also shown are ambulations in saline-treated mice following a saline challenge. D, Interval locomotor ambulations over 90 min in saline-treated mice that follow an injection of low-dose nicotine, high-dose nicotine, or saline. E, Interval locomotor ambulations over 90 min in amphetamine-treated mice. Ambulations that follow the first injection of amphetamine are compared with ambulations that follow an amphetamine challenge in withdrawal, with and without simultaneous treatment with nicotine in vivo. Low-dose nicotine had little effect on ambulations, whereas the higher dose of nicotine reduced ambulations to those observed during the last daily treatment of amphetamine. F, Interval locomotor ambulations over 90 min in saline-treated mice following an amphetamine challenge, with and without high-dose nicotine. G, Interval locomotor ambulations over 90 min in amphetamine-treated mice following a challenge with saline or high-dose nicotine are compared to ambulations in saline-treated mice challenged with saline. H, In MSNs from saline-treated mice, nicotine in vitro decreased the amplitude of the first eEPSC and increased the PPR. For all panels, *p<0.05, **p<0.01, ***p<0.001, paired t test. I, In MSNs from amphetamine-treated mice, nicotine increased the amplitude of the first eEPSC and decreased the PPR.