24 Sprague Dawley rats from ACS will be placed on restricted diet to bring them to ~ 85% of projected weight.
The rats will be habituated to the cages and test boxes used in the experiment. They will be introduced to the Nestle Nesquik cereal which is used as reinforcer
Week 1-Habituation The rats will be placed in a cage identical to their home cage for 10 min with Nesquik cereal. The rats will then be transferred to a test box for 10 minutes with Nesquik cereal. Record the time spent eating & the amount eaten in each 2 minute interval. Be very careful not to frighten rats & note if the rats spend any time immobilized with fear.
Week 2 Learning The rats will each receive 5 training trials of the odor learning. On the first trial the reward will be visible. The reward will be placed on the almond-scented sponge as well as in the centre hole. On the remaining 4 trials the reward is placed in the hole of the almond scented sponge. The other sponges are scented with orange or vanilla.
Apparatus Glass dishes and sponge (with Nesquik morsel).
Apparatus Test box showing rat in start position (top view).
Apparatus Test box showing rat in start position (front view).
Week 2 Learning (continued) Between trials the glass dishes will be switched with those from another group. The position of the 3 dishes will be varied in a systematic (quasirandom) way. The rat start position will not vary.
Week 2 Learning (continued) Record the time for the rat to obtain the reward in seconds. Record the number of commission (poking at hole of wrong sponge) & omission errors (not retrieving reward from correct sponge.) Allow the rat to eat the reward. Maximum trial duration is 5 minutes. Remove the rat from the test box.
Week 2 Learning (continued) On the basis of performance during acquisition, the rats will be divided into 3 groups of rats. 1. 8 rats will receive 4 mg/kg IP propranolol without memory reactivation (propranolol alone). 2. 8 rats will receive 4 mg/kg IP propranolol with memory reactivation (odor + propranolol). 3. 8 rats will receive IP physiological saline with memory reactivation (odor + vehicle).
Week 2 Reconsolidation The day after acquisition, rats in the two groups undergoing memory reactivation will be brought up to the lab. Each rat will be placed in a cage with a glass dish & sponge scented with almond for 90 seconds. There is no Nesquik reward. The rat will then be brought to a room adjacent to the lab & injected with either propranolol or saline. The rat is then returned to his home cage and transported back to the holding room.
Week 2 Reconsolidation (continued) Rats in the propranolol alone group will be injected with propranolol in the animal holding room and placed back into their home cages. Rats in this group will not be brought up to the classroom and will not be exposed to the almond odor.
Week 3 --- Trial 1--- Memory Test The rats will be placed in the test box with 3 glass dishes & scented sponges. There will be no reward. Record the latency to visit first dish. Record the latency to visit correct (almond) dish. Record errors of commission and omission.
Week 3 --- trials 2-5---Retraining These trials will be conducted exactly as done in week 2.
Week 3---Trial 6 Memory Test This is a 5 minute trial without a reward. Record: 1. Time spent investigating almond scented dish. 2. Time spent investigating other dishes (combined). 3. Number of nose pokes - almond scented sponge. 4. Number of nose pokes - other sponges (combined).