title: Environmental enrichment lowers stress-responsive hormones in singly housed male and female rats.
abstract: Structural and social aspects of an environmental system can influence the physiology and behavior of animals occupying that system. This study examined the physiological effects of environmental enrichment (EE) with Kong Toys and Nestlets on stress-responsive hormones of the hypothalamic-pituitary-adrenal (HPA) axis under basal and mild stress conditions in singly housed, jugular vein-cannulated, male and female rats. Animals of both sexes housed with EE had significantly lower baseline adrenocorticotropic hormone (ACTH) and corticosterone (CORT) concentrations compared to those housed without EE. ACTH responses to the mild stress of saline injection were significantly lower in female rats housed with EE. Interaction with the Kong Toys and Nestlets appears to have provided the rats with a diversion from monotonous cage life, resulting in lower HPA axis activity before and after mild stress. These results are important because low, stable baselines are essential for accurately discerning pharmacological and other influences on the HPA axis.
authors.affiliation: Center for Neurosciences Research, Allegheny-Singer Research Institute, Allegheny General Hospital, 8 S.T., 320 East North Avenue, Pittsburgh, PA 15212, USA.
authors.forename: Emily E
authors.initials: EE
authors.lastname: Belz
authors.forename: Jamilyn S
authors.initials: JS
authors.lastname: Kennell
authors.forename: R Kenneth
authors.initials: RK
authors.lastname: Czambel
authors.forename: Robert T
authors.initials: RT
authors.lastname: Rubin
authors.forename: Michael E
authors.initials: ME
authors.lastname: Rhodes
mesh_terms: D000324:Adrenocorticotropic Hormone / Q000097:blood; D000818:Animals; D004305:Dose-Response Relationship, Drug; D004777:Environment; D005260:Female; D006728:Hormones / Q000378:metabolism*; D006854:Hydrocortisone / Q000097:blood; D007030:Hypothalamo-Hypophyseal System / Q000502:physiology; D008297:Male; D010988:Play and Playthings; D051381:Rats; D017207:Rats, Sprague-Dawley; D012727:Sex Characteristics; D012934:Social Isolation; D013315:Stress, Psychological / Q000378:metabolism*
chemical_list: D006728:Hormones; D000324:Adrenocorticotropic Hormone; D006854:Hydrocortisone