Repeated restraint stress facilitates fear conditioning independently of causing hippocampal CA3 dendritic atrophy.
This study investigated whether 21 days of restraint stress (6 hr/day) and the subsequent hippocampal dendritic atrophy would affect fear conditioning, a memory task with hippocampal-dependent and hippocampal-independent components. Restraint-stressed rats were injected daily (21 days) with tianeptine (10 mg/kg; to prevent hippocampal atrophy) or vehicle then tested on fear conditioning (Days 23-25, with 2 tone-shock pairings) and open field (Day 25). Restraint stress enhanced freezing to context (hippocampal-dependent behavior) and tone (hippocampal-independent) and decreased open-field exploration, irrespective of whether tianeptine was given. Results confirmed that stress produced CA3 dendritic atrophy and tianeptine prevented it. Moreover, CA3 dendritic atrophy was not permanent but reversed to control levels by 10 days after the cessation of restraint stress. These data argue that different neural substrates underlie spatial recognition memory and fear conditioning.
Conrad
C D
CD
Department of Psychology, Arizona State University, Tempe 85287-1104, USA. conradc@asu.edu
LeDoux
J E
JE
Magariños
A M
AM
McEwen
B S
BS
D000818:Animals; D000929:Antidepressive Agents, Tricyclic / Q000494:pharmacology; D048429:Cell Size / Q000187:drug effects / Q000502:physiology; D003213:Conditioning, Psychological / Q000187:drug effects / Q000502:physiology*; D003712:Dendrites / Q000187:drug effects / Q000502:physiology*; D005106:Exploratory Behavior / Q000187:drug effects / Q000502:physiology; D005239:Fear / Q000187:drug effects / Q000502:physiology*; D006624:Hippocampus / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D008297:Male; D017966:Pyramidal Cells / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012149:Restraint, Physical; D013312:Stress, Physiological / Q000503:physiopathology*; D013841:Thiazepines / Q000494:pharmacology
D000929:Antidepressive Agents, Tricyclic; D013841:Thiazepines; C050504:tianeptine