The Rat Model Core (Core B) of the Emory University Silvio O. Conte Center~f6r the Neuroscience of Mental Disorders (CCNMD) represents an integral component of the overall Center. Core B will serve as the source of all rodents used by the individual preclinical Research Projects. In specific, Core B will produce and characterize a rat epigenetic early life stress (ELS) model associated with vulnerability to the development of a depression-like syndrome. Core B personnel will breed rodents, provide high quality animal care and uniformly applied neonatal manipulation protocols necessary to generate the ELS model, characterize the phenotype of all animals, ascertain the stage of the estrus cycle in adult female animals, and provide experimental manipulations as required by individual preclinical Research Projects within the Center. This epigenetic ELS model consists of Long Evans rats which are exposed to different rearing conditions from postnatal days (PND) 2-14, including: (1) animal facility reared (AFR) colony controls, (2) brief handling plus 15 min maternal separation (HMS 15) handling controls, (3) brief handling plus 180 min maternal separation (HMS 180). All individual Research projects will assess these animals for gender specific effects. Comparison of data obtained from these standardized rearing conditions among the various basic Research projects of this CCNMD will permit identification of central neurocircuit and intracellular mechanisms which are impacted by early life stress and which give rise to depressive-like syndrome; furthermore, since the animal models will be standardized, regression modeling can be used to elucidate interactions among these CNS systems in the genesis of this condition. Furthermore, the efficacy of various treatments (antidepressant, antisense, corticotropin releasing factor antagonist) in reversing aspects of depressive-like syndrome will be tested in these models. To this end, Core B will characterize the behavioral and HPA axis stress responsiveness of each animal, provide phenotypic screening for anhedonia, anxiety4fear-like behavior, as well as pr6viding surgical services such as chronic jugular catheterization, CNS guide cannula implantation, Alzet minipump preparation and implantation, resident intruder social defeat exposure, and other protocols as required by the Research Projects. Core B will provide characterized rats or will provide brain tissue, other tissue (adrenal, pituitary, etc), blood, or CSF from the HMS rats to the individual Research Projects. This organization has the advantage of maintaining consistency in animal handling and implementation of all protocols so that each preclinical Research Project receives identically characterized and treated animals for study.