Fig. 1

a Time schedule for nicotine-induced locomotor sensitization. Rats received nicotine (Nic) administrations (0.4 mg/kg s.c., twice a day) for 7 consecutive days, underwent 4 days of withdrawal, and then challenged with the same dose of Nic to induce locomotor sensitization; during the withdrawal period, the rats were orally administered MEGR (60 or 180 mg/kg/day, 4 times). b Effects of MEGR on Nic-induced locomotor sensitization in rats. Repeated Nic administrations induced a significant locomotor sensitization, which was inhibited by MEGR treatment. All data are expressed as means ± SEM (n = 7). S: saline, DW: distilled water, MEGR: methanol extract of G. radix, MEGR60: 60 mg/kg/day MEGR, MEGR180: 180 mg/kg/day. ^## P < 0.01, ^### P < 0.001 versus S/DW/S group; ^$$ P < 0.01, ^$$$ P < 0.001 versus Nic/DW/Nic group; ^@ P < 0.05, ^@@ P < 0.01, versus S/DW/Nic group; ^& P < 0.05 versus Nic/MEGR60/Nic group (one-way ANOVA followed by Newman-Keuls post-hoc test)