Bupropion induced changes in exploratory and anxiety-like behaviour in NMRI male mice depends on the age

• Age impacts in behaviour displayed by mice both in the plus-maze and hole-board.
• In the plus-maze, adolescent mice are more sensitive to bupropion than adults.
• Bupropion induces an anxiogenic-like effect in the plus-maze in adolescent mice.
• In the hole-board, adolescents and adults display similar sensitivity to bupropion.
• Bupropion reduces exploratory activity in the hole-board task.

The aim of this study was to assess the effects of the antidepressant bupropion on anxiety and novelty-seeking in adolescent mice of different ages and adults. Behavioural differences between early adolescent, late adolescent and adult NMRI mice were measured both in the elevated plus-maze and the hole-board tasks following acute administration of bupropion (5, 10, 15, 20 mg/kg) or saline. In the plus maze test, early and late adolescent mice treated with bupropion (10, 15 mg/kg, respectively) had lower percentages of entries in the open-arms compared to their vehicle controls. Adult mice treated with bupropion did not differ from their vehicle controls. These results suggest that the effect of this drug on anxiety-like behaviour in mice depends on the age, showing adolescents an anxiogenic-like profile. In the hole-board, adolescents showed more elevated levels of novelty-seeking than adults, exhibiting shorter latency to the first head-dip (HD) and a higher number of HD's. Bupropion increases the latency to the first HD and decreases the number of HD's in all age-groups, indicating a decline in exploratory tendency. Findings reveal that the age can modulate the behaviour displayed by mice in both animal models, and that adolescents are more sensitive to bupropion's anxiogenic effects.