Involvement of the mammillary bodies in spatial working memory revealed by cytochrome oxidase activity

• Published in: Brain research 2004-06, Vol.1011 (1), p.107-114
• Main Authors: Conejo, Nélida M, González-Pardo, Héctor, Vallejo, Guillermo, Arias, Jorge L
• Format: Article
• Language: English
• Subjects: Anatomical correlates of behavior; Animals; Animals, Newborn; Basolateral amygdala; Behavior, Animal; Behavioral psychophysiology; Biological and medical sciences; Cytochrome oxidase; Electron Transport Complex IV - metabolism; Female; Fundamental and applied biological sciences. Psychology; Histocytochemistry - methods; Male; Mammillary Bodies - enzymology; Mammillary Bodies - physiology; Mammillary body; Maze Learning - physiology; Memory, Short-Term - physiology; Neuronal metabolism; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Rats; Rats, Wistar; Reaction Time - physiology; Spatial Behavior - physiology; Spatial memory
• ISSN: 0006-8993; 1872-6240
• DOI: 10.1016/j.brainres.2004.03.025

In view of the inconclusive findings relating the nuclei of the mammillary bodies (MB) with spatial memory, we evaluated the oxidative metabolic activity of the medial and lateral nuclei of the mammillary bodies (MB) after training young rats (30 days) of both sexes in the Morris water maze. Different groups were trained in spatial working (WM) or reference memory (RM) tasks, respectively. The corresponding naı̈ve groups swam for the same amount of time as the trained groups but without the escape platform. Control groups were added that had not been manipulated in any way. No sex-related differences were detected in the working memory task although males exhibited better reference memory than females. Cytochrome oxidase (CO) activity, an endogenous metabolic marker for neuronal activity, was measured in all the groups. CO activity increased significantly in both MB nuclei of male and female rats only in the spatial working memory group. In addition, high CO activity in the lateral nucleus of the MB was linearly correlated with lower escape latencies in both sexes after training in the working memory task. No CO activity changes were found in the basolateral amygdala (BL) in any of the experimental groups. This nucleus was used as a control brain region because of its participation in emotional behavior. The results suggest a specific role of the MB nuclei in spatial working memory in both sexes.