title: Systemic and intra-rhinal-cortical 17-β estradiol administration modulate object-recognition memory in ovariectomized female rats.
abstract: Previous studies using the novel-object-preference (NOP) test suggest that estrogen (E) replacement in ovariectomized rodents can lead to enhanced novelty preference. The present study aimed to determine: 1) whether the effect of E on NOP performance is the result of enhanced preference for novelty, per se, or facilitated object-recognition memory, and 2) whether E affects NOP performance through actions it has within the perirhinal cortex/entorhinal cortex region (PRh/EC). Ovariectomized rats received either systemic chronic low 17-β estradiol (E2; ~20 pg/ml serum) replacement alone or in combination with systemic acute high administration of estradiol benzoate (EB; 10 μg), or in combination with intracranial infusions of E2 (244.8 pg/μl) or vehicle into the PRh/EC. For one of the intracranial experiments, E2 was infused either immediately before, immediately after, or 2 h following the familiarization (i.e., learning) phase of the NOP test. In light of recent evidence that raises questions about the internal validity of the NOP test as a method of indexing object-recognition memory, we also tested rats on a delayed nonmatch-to-sample (DNMS) task of object recognition following systemic and intra-PRh/EC infusions of E2. Both systemic acute and intra-PRh/EC infusions of E enhanced novelty preference, but only when administered either before or immediately following familiarization. In contrast, high E (both systemic acute and intra-PRh/EC) impaired performance on the DNMS task. The findings suggest that while E2 in the PRh/EC can enhance novelty preference, this effect is probably not due to an improvement in object-recognition abilities.
authors.affiliation: Center for Studies in Behavioral Neurobiology (CSBN), Department of Psychology, Concordia University, 7141 Sherbrooke Street West (SP-244), Montreal, Quebec H4B 1R6, Canada. Electronic address: Nicole.Gervais@concordia.ca.
authors.forename: Nicole J
authors.initials: NJ
authors.lastname: Gervais
authors.forename: Sofia
authors.initials: S
authors.lastname: Jacob
authors.forename: Wayne G
authors.initials: WG
authors.lastname: Brake
authors.forename: Dave G
authors.initials: DG
authors.lastname: Mumby
mesh_terms: D000281:Administration, Intranasal; D000818:Animals; D004958:Estradiol / Q000008:administration & dosage / Q000031:analogs & derivatives*; D005260:Female; D057967:Infusions, Intraventricular; D007275:Injections, Intravenous; D010052:Ovariectomy; D051381:Rats; D020318:Rats, Long-Evans; D021641:Recognition, Psychology / Q000187:drug effects*; D012153:Retention, Psychology / Q000187:drug effects; D014796:Visual Perception / Q000187:drug effects
chemical_list: C074283:estradiol 3-benzoate; D004958:Estradiol
keywords: 17-β Estradiol; Delayed nonmatch-to-sample; Entorhinal cortex; Novelty preference; Object-recognition memory; Perirhinal cortex