Mean (±SEM) distance traveled scores of rats (n = 8 per group) on the test day. Rats were challenged with NPA (0.25, 0.5, or 1 mg/kg) immediately before behavioral testing on PD 13, PD 17, PD 21, or PD 25. On the pretreatment day (i.e., 24 h earlier), rats had received a single injection of saline or NPA (0.5, 1, or 2 mg/kg).
a Significantly different from rats given 0 mg/kg NPA on the pretreatment day.