Methods

Chronic Stress Exposure (PND 2-9): On PND 2, litters receiving chronic stress will be fitted with a plastic-coated aluminum mesh platform sitting above the cage floor. Bedding will be reduced to sparingly cover the cage floor and one-half of a single paper towel will be provided for nesting material. Control litters will receive increased bedding and one-half of a single paper towel will be provided for nesting material. All dams and their respective litters will be undisturbed on PNDs 2-9. On PND 10, all rats will be moved to clean cages containing standard nesting material (Molet et al., 2016).

aELS Memory Retention Test (Context A): On PND ~90, memory of the ELS experience will be assessed. Rats will be placed into Context A for 8 minutes without footshock and then transported back to their home cages at the end of the session. 

Adult Fear Conditioning (Context B): Fear conditioning will occur on PND ~91. Animals will first be transported in their home cages to a dark room, then will be moved in a blackened plastic box to Context B. Rats will receive either 0 or 1 footshock (1 mA, 1s) 180 seconds after being placed in Context B. Rats will then be removed from the chamber 30 seconds after termination of the shock. 

Adult Fear Test (Context B): The next day (PND ~92), rats will be placed back into Context B (transported as before) for 8 minutes without footshock to assess fear memory. Rats will be transported back to their home cages following the session. 

Open Field Testing: On PND ~93, rats will be transported to the laboratory room containing the open field. Rats will be placed in the center of the open field to begin the test session. The test will consist of an 8-minute exposure to the open field. During the first 4 minutes, the room will be dark and during the final 4 minutes the open field arena will be illuminated. The outer perimeter of the apparatus will be designated to measure thigmotaxis, an indicator of anxiety-like behavior.