title: The effects of chronic stress on hippocampal morphology and function: an evaluation of chronic restraint paradigms.
abstract: Chronic restraint stress for 6 h/21 days causes hippocampal CA3 apical dendritic retraction, which parallels spatial memory impairments in male rats. Recent research suggests that chronic immobilization stress for 2 h/10 days induces CA3 dendritic retraction [Vyas, A., Mitra, R., Shankaranarayana Rao, B.S., Chattarji, S., 2002. Chronic stress induces contrasting patterns of dendritic remodeling in hippocampal and amygdaloid neurons. J. Neurosci. 22, 6810-6818.] and questions whether CA3 dendritic retraction and spatial memory deficits can be produced sooner than found following 6 h/21 days of restraint stress. Therefore, this study investigated the effects of four different durations of chronic restraint stress (varied by hours/day and total number of days) and the subsequent effects on hippocampal CA3 morphology and spatial memory in the same male Sprague-Dawley rats. The results showed that only rats exposed to the 6 h/21 days restraint paradigm exhibited CA3 apical dendritic retraction, consistent spatial memory deficits, and decreased body weight gain compared to experimental counterparts and controls. While chronically stressing a rat with wire mesh restraint has a physical component, it acts primarily as a psychological stressor, and these findings support the interpretation that chronic psychological stress produces hippocampal-dependent cognitive deficits that are consistent with hippocampal structural changes. Differences in stress effects observed across different studies may be due to rat strain, type of stressor, and housing conditions; however, the current findings support the use of chronic restraint stress, with wire mesh, for 6 h/21 days as a reliable and efficient method to produce psychological stress and to cause CA3 dendritic retraction and spatial memory deficits in male Sprague-Dawley rats.
authors.affiliation: Department of Psychology, Arizona State University, Tempe, AZ 85287-1104, USA. kjmclaugh@hotmail.com
authors.forename: Katie J
authors.initials: KJ
authors.lastname: McLaughlin
authors.forename: Juan L
authors.initials: JL
authors.lastname: Gomez
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Baran
authors.forename: Cheryl D
authors.initials: CD
authors.lastname: Conrad
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001835:Body Weight / Q000502:physiology; D003712:Dendrites / Q000473:pathology / Q000648:ultrastructure; D006624:Hippocampus / Q000473:pathology* / Q000648:ultrastructure; D008297:Male; D018782:Maze Learning / Q000502:physiology; D009474:Neurons / Q000473:pathology / Q000648:ultrastructure; D051381:Rats; D017207:Rats, Sprague-Dawley; D012149:Restraint, Physical / Q000379:methods*; D016622:Silver Staining / Q000379:methods; D013315:Stress, Psychological / Q000209:etiology* / Q000473:pathology*; D013997:Time Factors