Behavioural Training Prior to Infusions
Prior to surgery, all rats were habituated to the maze for four sessions. During the first habituation session, multigrain hoops (Crownfield, UK) were placed in the food wells in the choice-arms, and the rats were placed in the maze in cage-pairs to explore the start arm for 5 minutes. Then, they were placed in the choice-arms where they could collect food rewards for a further 5 minutes. During sessions 2 and 3, the above procedure was repeated for each rat individually for 5 minutes. In session 4, the aluminium barrier was introduced at the entrance of one arm and the rats allowed to explore for 5 minutes. The same procedure was repeated but now the barrier blocked the other arm. The food in the wells was continuously replaced. The rats were then run on the ‘Standard’ T-maze procedure (see below) for 5 to 9 days and the animals for surgery were selected, based on their performance and willingness to run.
At least seven days post-surgery, and after signs of full recovery, the animals were retrained on the Standard T-maze task for 6 to 10 days, until they reached at least 87.5% on two consecutive sessions. The infusion trials for Standard T-maze then followed, commencing at least three weeks after surgery.
The rats were then trained on the next T-maze condition for 3 to 5 days, followed by the infusion trials for that condition. An additional, infusion-free training day was provided if there had been a gap of more than two days between infusion sessions. An infusion-free training session was also given on the day between the two clozapine infusions, to help performance return to baseline (Figure 1). This testing regime was repeated for the remaining behavioural conditions (Figures 1, 2). The order of clozapine, saline, and injection-free sessions for the various conditions was balanced between the two cohorts (Figure 1).