Figure 5.

Schematic of conditioned place preference procedure (CPP). The CPP procedure consisted of three phases: habituation (one session), conditioning (eight sessions), and place preference test (one session). Immediately before each daily session, each animal received an intraperitoneal injection of saline or 0.1 mg/kg decynium 22 (D22), followed 60 min later by a second injection of saline or 1 mg/kg amphetamine (AMPH). After the second injection, mice were immediately placed in the center of the apparatus. For the habituation session, all mice received saline and were placed in the apparatus for 30 min (min) on a floor covered with paper. Thirty minute conditioning sessions were held on the following 8 days. Conditioning consisted of pairing one floor type with the injection of amphetamine and the other floor type with the injection of saline. The day after the last conditioning session, the 30 min floor preference test, using a floor in which each half consisted of each floor type, was conducted in mice having received saline. Place preference was measured by subtracting the amount of time spent on the drug-paired floor from the amount of time spent on the saline-paired floor. Figure created with Biorender.com.