DIETARY COPPER AND MAGNESIUM EFFECTS ON ACTIVITY, LEARNING, MEMORY AND ANXIETY IN RATS

Authors: Penland, James; SPEAKER, KAREN - U NORTH DAKOTA; MOULTON, PATRICIA - U NORTH DAKOTA

Submitted to: North Dakota Academy of Science Proceedings
Publication Type: Other
Publication Acceptance Date: 4/25/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: The relationship between copper (Cu) and magnesium (Mg) nutriture and behavior, particularly in adults, has received little attention. Both minerals are of potential relevance to behavior because of their important roles in brain function. Two controlled studies were conducted to directly examine the effects on several distinct behaviors of feeding mature rats either 0.5 or 6 ppm Cu (Study I) and either 50 or 500 ppm Mg (Study II). Diets were fed for 10 weeks. In both studies, horizontal, vertical and repeated (stereotypic) movements were measured with an activity monitor, learning and memory with a water maze, and anxiety with a plus maze. A stressor (loud noise) was introduced during part of the period when activity was being monitored. Low intakes of both Cu and Mg were associated with an increase in generalized activity. Low Cu intake also resulted in more stereotypic behavior during presentation of the stressor, whereas low Mg intake resulted in increased stereotypic behavior regardless of the presence of the stressor. Low Cu intake was associated with poorer performance on measures of learning, whereas low Mg intake was associated with poorer performance on measures of memory. Neither Cu nor Mg showed effects on direct measures of anxiety. Sex of the rat frequently determined whether Cu, but not Mg, intake affected activity and learning and memory. Findings indicate that both Cu and Mg deprivation have functional consequences for behavior. Future studies must further specify their role in behavior and establish minimum intakes required to avoid negative consequences.

Technical Abstract: The relationship between copper (Cu) and magnesium (Mg) nutriture and behavior, particularly in adults, has received little attention. Both mineral elements are of potential relevance to behavior because of their importance in neurotransmitter metabolism and because studies have shown a relationship between dietary intakes and brain electrophysiology. Two controlled studies with mature rats were conducted to directly examine the effects of dietary Cu and Mg on several cognitive and emotional behaviors. In the Cu study, 60 (30 male) Long-Evans rats, aged 85-d, were fed an AIN93G diet containing either 0.5 or 6.0 ug/g Cu for 10 wks. In the Mg study, 100 (50 male) 14-month old Long Evans rats were fed an AIN93M diet containing either 50 or 500 ug/g Mg for 10 wks. Horizontal, vertical and stereotypic movements were measured with an activity monitor, learning and memory with a water maze, and anxiety with an elevated plus maze. An auditory stressor was introduced during part of activity monitoring. Low intakes of both Cu and Mg were associated with an increase in generalized activity. Low Cu intake also resulted in more stereotypic behavior during presentation of an auditory stressor, whereas low Mg intake resulted in increased stereotypic behavior regardless of the presence of the stressor. Low Cu intake was associated with poorer learning performance, whereas low Mg intake was associated with poorer memory performance. Neither Cu nor Mg showed effects on direct measures of anxiety. Sex frequently interacted with Cu intakes on measures of activity and learning and memory. Findings indicate that both Cu and Mg deprivation have functional consequences at the behavioral level. Future studies must specify their role in behavior and establish minimum intakes required to avoid negative consequences.