Assessment of the effects of sex and sex hormones on spatial cognition in adult rats using the Barnes maze

• Published in: Hormones and behavior Vol. 66; no. 2; pp. 298 - 308
• Main Authors: Locklear, M.N., Kritzer, M.F.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 01.07.2014; Elsevier; Elsevier BV
• Subjects: Animal memory; Animal reproduction; Animals; Barnes maze; Behavioral psychophysiology; Biological and medical sciences; Estradiol - pharmacology; Female; Fundamental and applied biological sciences. Psychology; Gonadal hormones; Gonadal Steroid Hormones - metabolism; Hormones; Hormones and behavior; Male; Maze Learning - physiology; Orchiectomy; Problem Solving - drug effects; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Psychomotor Performance - drug effects; Rats; Rats, Sprague-Dawley; Rodents; Sex Characteristics; Sex difference; Sexual Behavior, Animal - physiology; Space Perception - physiology; Spatial reference memory; Spatial working memory; Testosterone - pharmacology; Spatial working memory; Gonadal hormones; Spatial reference memory; Barnes maze; Sex difference; Hormone; Reference memory; Evaluation; Rat; Spatial cognition; Rodentia; Sex; Vertebrata; Mammalia; Adult animal; Working memory; Spatial memory
• ISSN: 0018-506X; 1095-6867
• DOI: 10.1016/j.yhbeh.2014.06.006

Although sex differences and hormone effects on spatial cognition are observed in humans and animals, consensus has not been reached regarding exact impact on spatial working or reference memory. Recent studies in rats suggest that stress and/or reward, which are often different in tasks used to assess spatial cognition, can contribute to the inconsistencies in the literature. To minimize the impact of these sex- and sex hormone-sensitive factors, we used the Barnes maze to compare spatial working memory, spatial reference memory and spatial learning strategy in adult male, female, gonadectomized (GDX) male, and GDX male rats supplemented with 17β-estradiol (E) or testosterone propionate (TP). Rats received four acquisition trials, four trials 24h later, and a single retention trial one week after. Males and females acquired the task during the first four trials and retained the task thereafter. In contrast, GDX rats took longer to acquire the task and showed retention deficits at 1week. All deficits were attenuated similarly by TP and E. Assessment of search patterns also showed that strategies in the males transitioned from random to spatially focused and eventually direct approaches to the goal. However, this transition was faster in control and GDX-TP than in GDX and GDX-E rats. In contrast, the females almost invariantly followed the maze edge in thigmotactic, serial searches. Thus, while Barnes maze reveals activational, in part estrogenic effects on spatial cognition in males, its amenability to animals' use of multiple strategies may limit its ability to resolve mnemonic differences across sex. •We test sex and hormone effects on spatial working and spatial reference memory.•Potential reward and stress confounds were minimized by using the Barnes maze.•Gonadectomy impairs spatial working but not spatial reference memory in male rats.•Both testosterone propionate and 17β-estradiol rescue gonadectomy-induced deficits.•Sex differences were observed in search strategy preference.