Y-Maze Behavioral Task
Aversive Y-maze Discrimination Task
The animals in this experiment are givenone training trial per day for 6 consecutive days. Training begins by placing each animal in the stem of the Y-maze. The animals are then given up to 5 minutes to locate and consume 10 pellets (45mg each) placed in a food cup on the rear wall of the right alley and 5 pellets placed in the food cup at the very end of the left alley. A trial ends when all 15 of the food pellets are retrieved and consumed in the maze. The animals are then allowed to freely explore the alleys for an additional 20 s before being returned to their home cages. Digital timers are used to record a) the initial latency to enter either alley at the start of training b) the seconds spent in each alley before all pellets were consummed c) the seconds spent in an alley after pellets were consummed d) the cumulative latency to consume all pellets from the beginning of a trial and e) the time spent in the non-baited stem or start alley of the y-maze.
On Day 6 of training, the cardboard insert covering the floor of the maze is removed from only the right alley to expose the stainless steel footshock plates. As in the previous days of training, each animal was allowed to consume all of the food pellets placed in the left and right alley. However, when the subject returns to the right alley and approaches the empty food cup, a mild footsh ock is administered for 0.5 seconds in that alley. Immediately after the footshock, the animal is removed from the maze and randomly assigned to a drug treatment group.
Retention of the footshock training is assessed on Day 7 and 8 under two separate conditions. The latency to enter the right alley and the number of seconds to consume all of the pellets in the right alley where footshock was received during training serves as indices of retention on both tests. On the first retention test, the cardboard insert is returned to the right alley as during the first 5 days of training. Thus, the stainless steel plates from which footshock was delivered on day 6 are concealed from the animals on this retention test. This manipulation provides an assesment of the animals memory of the footshock training in the absence of the most salient contextual cue associated with the footshock (i.e. the stainless steel footshock plates). During the second retention test given on Day 8, the cardboard insert in the right alley is removed to expose the stainless steel plates. On this day, the animals are exposed to identical contextual cues that were present on the day of footshock training. The two different tests are expected to reveal whether a) memory for an emotional experience is facilitated by specific pharmacological agents under normal testing conditions and b) to assess whether these treatments affect retention under conditions in which memory is weakened by removing salient cues that are linked or associated with an arousing event such as footshock.
Appetitive Y-Maze Light-Dark Discrimination Task
During training each animal is given 25 light-dark discrimination trials on Day 1 and an additional 10 training trials on Day 2. For Trial 1 on each day of training and on the subsequent retention tests, subjects are placed in the stem of the maze facing the rear wall with the cue light off in that arm and the door raised. Once the door is lowered, the rats are allowed to choose between a dark unbaited arm or an illuminated arm baited with 3 sucrose pellets. After entering one of the arms, the door is raised enclosing the rat in that choice section for a period of 10 seconds. A new arm is then baited and the back panel in that arm illuminated. The next trial then begins by lowering the door and allowing the animal to choose between the new dark unbaited arm or the illuminated baited arm. After the 10 training trials on Day 2, each subject is removed from the maze and given a drug treatment. Retention tests are given on Days 4 and 9 and consisted of the same procedures that were used during training (see below). Mean percentage of correct responses and number of trials to reach 5 total correct responses serve as indices of retention.