title: Differential effects of acute progesterone administration on spatial and object memory in middle-aged and aged female C57BL/6 mice.
abstract: The present study examined the effects of acute progesterone administration on hippocampal-dependent memory consolidation in ovariectomized middle-aged (16 months old) and aged (22 months old) female mice. Spatial memory was tested in a 2-day Morris water-maze task and object memory was tested using an object recognition task with 24- and 48-h delays. Immediately after water-maze training, mice received i.p. injections of vehicle, or 5.0, 10.0, or 20.0 mg/kg of water-soluble progesterone. Twenty-four hours later, retention of the platform location was tested. No overnight forgetting of the platform location was observed in middle-aged vehicle-treated mice. Acute progesterone administration had no effect on spatial memory in middle-aged mice. However, aged vehicle-treated mice demonstrated impaired memory for the platform location on Day 2 relative to Day 1. Twenty mg/kg, but not 5 or 10 mg/kg, progesterone reversed these deficits, suggesting that 20 mg/kg progesterone can improve spatial memory in aged females. In the object recognition task, mice explored two identical objects and then immediately received vehicle or progesterone injections. In middle-aged mice, 10 and 20 mg/kg progesterone enhanced object memory consolidation, relative to chance, after 24-h, but all doses were ineffective after 48-h. In aged mice, 10 mg/kg progesterone enhanced object memory consolidation, relative to chance, after 24 h, whereas both 5 and 10 mg/kg progesterone enhanced memory after 48 h. Together, these results indicate that acute progesterone differentially enhances hippocampal-dependent memory in middle-aged and aged females.
authors.affiliation: Department of Psychology, Yale University, 2 Hillhouse Avenue P.O. Box 208205, New Haven, CT 06520, USA.
authors.forename: Michael C
authors.initials: MC
authors.lastname: Lewis
authors.forename: Patrick T
authors.initials: PT
authors.lastname: Orr
authors.forename: Karyn M
authors.initials: KM
authors.lastname: Frick
mesh_terms: D000375:Aging / Q000187:drug effects*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D005106:Exploratory Behavior / Q000187:drug effects*; D005260:Female; D006624:Hippocampus / Q000187:drug effects; D018782:Maze Learning / Q000187:drug effects*; D011939:Mental Recall / Q000187:drug effects*; D051379:Mice; D008810:Mice, Inbred C57BL; D009949:Orientation / Q000187:drug effects*; D010364:Pattern Recognition, Visual / Q000187:drug effects*; D011374:Progesterone / Q000494:pharmacology*; D012153:Retention, Psychology / Q000187:drug effects
chemical_list: D011374:Progesterone