Fig. 4.

Effects of intra-NAc BDNF infusions on locomotor activation after a low dose of cocaine (5 mg/kg). At 5 mg/kg cocaine, a subthreshold sensitization dose, animals infused with BDNF developed sensitization, whereas vehicle-infused animals did not show sensitization. On day 8, there were no differences, whereas on days 9–12 there were significant differences between the groups at each of the time points shown (*p < 0.05). Differences were as follows: day 9 BDNF-infused animals had increased locomotor rates at 10 and 20 min after cocaine (F_(1,10) = 6.33 and 5.97, respectively;p < 0.05); day 10 increases were found at 10 min after cocaine (F_(1,10) = 5.21;p < 0.05); on day 11, a significant difference between vehicle-infused and BDNF-infused animals was observed at 10, 20, 30, and 40 min after the cocaine injection (F_(1,10) = 5.33, 12.03, 7.10, and 8.94, respectively; p < 0.05); on day 12, there continued to be differences between the BDNF-infused and vehicle-infused animals; significant differences between the groups were found at 10 min after the cocaine injection and a trend at 30 min (F_(1,10) = 7.71 and 3.76, respectively;p < 0.05 and 0.08, respectively). There were no differences between the groups before the cocaine injections. Data are expressed as the mean ± SEM number of photocell disruptions over the 30 min test period.