Figure 1.

Effects of acute nicotine on locomotion in preproenkephalin-deficient (black bars) and wild-type (white bars) mice. Horizontal (A) and vertical (B) locomotion were measured 5 min after nicotine administration (0, 1, 3, and 6 mg/kg, s.c.). Data are expressed as mean ± SEM of photocell counts during a 10 min period in wild-type (saline, n = 34; nicotine, 1 mg/kg, n = 21; nicotine, 3 mg/kg, n = 20; nicotine, 6 mg/kg, n = 15) and knock-out (saline, n = 33; nicotine, 1 mg/kg, n = 17; nicotine, 3 mg/kg, n = 18; nicotine, 6 mg/kg, n = 15) mice. ^★★p < 0.01, when compared with the saline group of the same genotype (Dunnett's test).