Lable Enzyme Immunoassay Kit (Assay Designs, Michigan, USA), according to the manufacturer’s instructions.Materials and Methods 
Ethics StatementAll experimental procedures were conducted in accordance with the Guide for the Care and Use of Laboratory Animals of the National Institutes of Health. The relevant animal protocol was approved by the Epigenetics University of Houston Institutional Animal Care and Use Committee (protocol number 10?39).Animals and CUS ParadigmAdult male Long Evans rats (3 months old at the start of experiments) were individually housed in clear plastic cages with ad libitum food and water. Upon arrival, animals habituated for one week to the vivarium environment. CUS was administered as previously described [9,16] for 14 days. Briefly, two different daily stressors (e.g., tilted cages, vinegar-laced water, exposure to strobe light, predator odor and predator calls) as well as the timing of the stressors, were determined by a random number generator. All stressors were conducted in a room separate from where control animals were housed.HistologyOne day after the end of CUS, control (n = 9) and stress (n = 9) animals were overdosed with anesthetic and intracardially perfused with 4 paraformaldehyde. Brains were removed and post-fixed overnight, then stored in 30 sucrose. Brains were cut into 50 mm sections on a freezing microtome and stored in cryoprotectant in 96-well microtiter plates at 220uC. To label doublecortin-positive (DCX+) cells, standard immunohistochemical procedures were used to process every sixth section throughout the rostrocaudal extent of the hippocampus. Following treatment in 0.6 hydrogen peroxide and blocking in 3 Epigenetic Reader Domain donkey serum, sections were incubated for 72 hours at 4uC in primary antibody (goat anti-DCX, Santa Cruz Biotechnology, Inc., CA, USA, 1:100), rinsed and then incubated overnight in secondary antibody (donkey anti-goat, Jackson ImmunoResearch, PA, USA, 1:250). Sections were then processed with a standard ABC kit, and reacted in DAB according to the manufacturer’s instructions (Vector Labs, CA, USA). Sections were counterstained in methyl green, mounted onto slides and coverslipped. For CldU and IdU immunohistochemistry, we followed the methods of Vega and Peterson [17]. Separate 1-in-6 series of sections were pre-treated in 0.3 hydrogen peroxide, rinsed 23727046 in TBS, and then incubated in 2N HCl at 37uC for 10 minutes. Sections were then washed in 0.1M borate buffer for 10 minutes and rinsed six times in TBS. Thereafter, they were treated as described above. The antibodies used were mouse anti-BrdU (Becton Dickenson, NJ, USA, 1:100) and rat anti-BrdU (Accurate Chemical, NY, USA, 1:250) for CldU and IdU respectively. TheAdministration of Thymidine AnalogsIn order to quantify the impact of CUS on survival of progenitor cells in the DG, control (n = 9) and stressed (n = 9) animals were injected with iododeoxyuridine (IdU, MP Biomedicals, OH, USA, 57.5 mg/kg, i.p.) daily for the first 5 days of CUS. To quantify the effect of CUS on proliferation of DG progenitor cells, the same rats were injected with chlorodeoxyuridine (CldU, Sigma-Aldrich, MO, USA, 42.5 mg/kg, i.p.) 2 hours prior to sacrifice [17].Radial Arm Water Maze (RAWM)The day after CUS exposure, rats (control, n = 15; stress, n = 15) were tested for spatial learning and memory performance using a one-day learning paradigm in the RAWM [18], which is a hippocampal-dependent task [19,20]. The RAWM consists of six stainless steel, V-shaped arms.Lable Enzyme Immunoassay Kit (Assay Designs, Michigan, USA), according to the manufacturer’s instructions.Materials and Methods Ethics StatementAll experimental procedures were conducted in accordance with the Guide for the Care and Use of Laboratory Animals of the National Institutes of Health. The relevant animal protocol was approved by the University of Houston Institutional Animal Care and Use Committee (protocol number 10?39).Animals and CUS ParadigmAdult male Long Evans rats (3 months old at the start of experiments) were individually housed in clear plastic cages with ad libitum food and water. Upon arrival, animals habituated for one week to the vivarium environment. CUS was administered as previously described [9,16] for 14 days. Briefly, two different daily stressors (e.g., tilted cages, vinegar-laced water, exposure to strobe light, predator odor and predator calls) as well as the timing of the stressors, were determined by a random number generator. All stressors were conducted in a room separate from where control animals were housed.HistologyOne day after the end of CUS, control (n = 9) and stress (n = 9) animals were overdosed with anesthetic and intracardially perfused with 4 paraformaldehyde. Brains were removed and post-fixed overnight, then stored in 30 sucrose. Brains were cut into 50 mm sections on a freezing microtome and stored in cryoprotectant in 96-well microtiter plates at 220uC. To label doublecortin-positive (DCX+) cells, standard immunohistochemical procedures were used to process every sixth section throughout the rostrocaudal extent of the hippocampus. Following treatment in 0.6 hydrogen peroxide and blocking in 3 donkey serum, sections were incubated for 72 hours at 4uC in primary antibody (goat anti-DCX, Santa Cruz Biotechnology, Inc., CA, USA, 1:100), rinsed and then incubated overnight in secondary antibody (donkey anti-goat, Jackson ImmunoResearch, PA, USA, 1:250). Sections were then processed with a standard ABC kit, and reacted in DAB according to the manufacturer’s instructions (Vector Labs, CA, USA). Sections were counterstained in methyl green, mounted onto slides and coverslipped. For CldU and IdU immunohistochemistry, we followed the methods of Vega and Peterson [17]. Separate 1-in-6 series of sections were pre-treated in 0.3 hydrogen peroxide, rinsed 23727046 in TBS, and then incubated in 2N HCl at 37uC for 10 minutes. Sections were then washed in 0.1M borate buffer for 10 minutes and rinsed six times in TBS. Thereafter, they were treated as described above. The antibodies used were mouse anti-BrdU (Becton Dickenson, NJ, USA, 1:100) and rat anti-BrdU (Accurate Chemical, NY, USA, 1:250) for CldU and IdU respectively. TheAdministration of Thymidine AnalogsIn order to quantify the impact of CUS on survival of progenitor cells in the DG, control (n = 9) and stressed (n = 9) animals were injected with iododeoxyuridine (IdU, MP Biomedicals, OH, USA, 57.5 mg/kg, i.p.) daily for the first 5 days of CUS. To quantify the effect of CUS on proliferation of DG progenitor cells, the same rats were injected with chlorodeoxyuridine (CldU, Sigma-Aldrich, MO, USA, 42.5 mg/kg, i.p.) 2 hours prior to sacrifice [17].Radial Arm Water Maze (RAWM)The day after CUS exposure, rats (control, n = 15; 
stress, n = 15) were tested for spatial learning and memory performance using a one-day learning paradigm in the RAWM [18], which is a hippocampal-dependent task [19,20]. The RAWM consists of six stainless steel, V-shaped arms.
