Conditioned Place Preference Protocol

CPP was performed as described(Land et al., 2008 (link)). The apparatus consisted of two chambers with distinct visual cues (vertical or horizontal black and white stripes) and one center chamber. Each chamber was filled with bedding, and the chambers were wiped down with water between sessions. Habituation and baseline chamber preference: On days 1 and 2, animals were allowed access to all three chambers for 30 min and the baseline values for time spent in each chamber were derived from day 2. Vehicle/drug chamber pairings for each mouse were then randomly assigned. Pairing: Days 3-5 served as chamber pairing days. On these days animals were first injected with vehicle in the AM and confined to the designated chamber for 30 min. At least 4 hrs later animals were injected with the assigned drug conditioned and were confined to the opposite chamber for 30 min. Post-test: On day 6, animals were again allowed free access to all three chambers for 30 min.
Video was recorded from the top of each chamber at rate of 25 fps using Bonsai open-source software(Lopes et al., 2015 (link)). Videos were then analyzed using Ethovision 14 (Noldus Information Technology). Ethovision was used to calculate the amount of time spent in each chamber and the amount of distance travelled during conditioned sessions.