Experimental timeline. Separate cohorts of male rats at PND 28 were randomly assigned to either the CTRL-CTRL, SDS-CTRL, CTRL-SPS, or SDS-SPS groups. Rats were subjected to 30 min social defeat stress (SDS) daily for seven consecutive days from postnatal day (PND) 28 to 34, and then to the single prolonged stress (SPS) paradigm in adulthood (PND 90). Thirty days after SPS exposure, two separate groups of rats were exposed to a behavioral test battery. The first group was exposed to open field (PND 120) and auditory fear conditioning (PND 122) tasks, and the second one was exposed to acoustic startle response (PND 120) and Morris water maze (PND 122) tasks. One week after the last behavioral task, rats were killed, and the bilateral hippocampus was immediately dissected from each animal for biochemical analyses.