Figure 2. Timeline of developmental fluoxetine (FLX) treatment and cocaine place conditioning procedures.

Separate groups of adolescent (postnatal day [PD]-35) and adult (PD 65) male c57bl/6 mice received vehicle (VEH) or fluoxetine (FLX; 20 mg/kg) for 15 consecutive days. Twenty-one days after the last exposure to FLX, mice were screened for side-preference bias (preconditioning), and were randomly assigned to receive cocaine (0, 2.5, 5, 10, or 20 mg/kg) for four consecutive days (conditioning). During the conditioning trials, mice were initially administered with saline and confined to the preferred compartment for 25 min. Three h later, mice were administered with cocaine, and confined to the opposite side of the chamber (25 min). On test day (preference), mice were given access to the entire apparatus (25 min), and the time spent in each compartment of the testing chamber was recorded.