Mice were placed into photocell activity cages for 10 min after 30 min s.c. administration of bupropion (3 and 10 mg/kg) in α4 KO (A), α6 KO (B) and WT mice (C). The C57BL/6J mice (C) were injected s.c. DHβE (3 mg/kg) or vehicle (saline) 20 min before bupropion treatment. After 30 min bupropion (3 and 10 mg/kg, s.c.) or vehicle (saline) injection, mice were tested in activity cages. Results were expressed as the mean ± SEM as the number of photocell interruptions of α4 6 (WT) and 6 (KO); α6 8 (WT) and 8 (KO); . * p < 0.05, significantly different from vehicle group in WT animals or in vehicle pretreated group C57BL/6J mice; + p < 0.05, significantly different from vehicle group in KO animals or in DHβE pretreated group. Bup: bupropion