Submitted to: Nutritional Neuroscience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 15, 2006
Publication Date: February 1, 2006
Repository URL: http://handle.nal.usda.gov/10113/46090
Citation: Nielsen, F.H., Penland, J.G. 2006. Boron deprivation alters rat behaviour and brain mineral composition differently when fish oil instead of safflower oil is the diet fat source. Nutritional Neuroscience. 9(1-2):105-112. Interpretive Summary: Boron and long-chain omega-3 polyunsaturated fatty acids known as DHA (docosahexaenoic acid) and EPA (eicosapentaenoic acid) found in fish oil affect many of the same biological processes apparently through influencing the physical and chemical makeup and thus the function of cell membranes. Boron, DHA and EPA have been found to promote good brain function based on measurements of brain electrical activity. However, it has not been determined whether boron deprivation, which causes changes in brain electrical activity, also changes rat behavior. Additionally, the positive effect of fish oil on behavior has not been consistently found; this inconsistency may have been caused by variable boron intakes. Thus, an experiment was performed to determine whether boron deprivation affects rat behavior and whether behavioral responses to boron deprivation are modified by differing amounts of DHA plus EPA in the diet. Female rats were fed boron-deficient diets (0.1 mg boron/kg) and supplemented with either 0 or 3 mg boron/kg diet. The dietary fat source was either fish oil or safflower oil (does not contain DHA or EPA). Boron-deficient rats were less active than boron-supplemented rats when fed safflower oil. Feeding fish oil instead of safflower oil reduced the difference in activity between boron-deficient and boron-supplemented rats. Behavioral reactivity (anxiety) or exploratory activity of boron-deficient rats fed fish oil was noticeably different than that of rats fed the other diets. These rats also had the lowest copper and zinc concentrations in brain. Because zinc and copper deprivation have been found to be detrimental to animal brain function and behavior, the behavioral reactivity change in the boron-deficient rats fed fish oil may not have been desirable. Both boron deprivation and safflower oil also increased an indicator of oxidative stress in rats. The findings indicate that both boron and fish oil influence rat behavior and brain composition, and the influence of one these bioactive substances can be altered by changing the intake of the other. Findings were also obtained that suggest rat behavior is affected by an interaction between boron and fish oil because both affect oxidative metabolism and act at the cell membrane level. A combined increased intake of boron and fish oil apparently promotes good brain function and behavior.
Technical Abstract: An experiment was performed to determine whether boron deprivation affects rat behaviour and whether behavioural responses to boron deprivation are modified by differing amounts of dietary long-chain omega-3 fatty acids. Female rats were fed diets containing 0.1 mg g-1 boron in a factorial arrangement with dietary variables of supplemental boron at 0 and 3 mg kg-1 and fat sources of 75 g kg-1 safflower oil or 65 g kg-1 fish (menhaden) oil plus 10 g kg-1 linoleic acid. After 6 wk, six females per treatment were bred. Dams and pups continued on their respective diets through gestation, lactation and after weaning. Behavioural tests were performed on 13-15 male rats in each dietary treatment. At ages 6 and 19 wk, auditory startle was evaluated with an acoustic startle system and avoidance behaviour (specifically anxiety) was evaluated by using an elevated plus-maze. At ages 7 and 20 wk, spontaneous behaviour activity was evaluated with a photobeam activity system. A brightness discrimination test was performed on the rats between age 15 and 16 wk. The rats were euthanized at age 21 wk for the collection of tissues and blood. Brain and kidney mineral composition was determined by coupled argon plasma atomic emission spectroscopy. Plasma total glutathione was determined by HPLC, and total cholesterol and 8-iso-prostaglandin F2alpha were determined by using commercially available kits. Boron-deficient rats were less active than boron-adequate rats when fed safflower oil based on reduced number, distance and time of horizontal movements, front entries, margin distance, and vertical breaks and jumps in the spontaneous activity evaluation. Feeding fish oil instead of safflower oil attenuated the activity response to boron deprivation. In the plus maze evaluation, the behavioural reactivity of the boron-deficient rats fed fish oil was noticeably different than the other three treatments. They made more entries into both open and closed arms, and the center area, and thus visited more locations. The boron-deficient rats fed fish oil also exhibited the lowest copper and zinc and highest boron concentrations in brain; the lowest zinc and magnesium and highest iron and boron concentrations in kidney; and the highest plasma glutathione concentration. Both boron deprivation and safflower oil increased plasma 8-iso-prostaglandin F2alpha. Conclusions: Both dietary boron and long-chain omega-3 fatty acid diet influence rat behaviour and brain composition, and the influence of one these bioactive substances can be altered by changing the intake of the other. Brain and kidney mineral and plasma cholesterol, glutathione and 8-iso-prostaglandin findings suggest that rat behaviour is affected by an interaction between boron and fish oil because both affect oxidative metabolism and act the cellular membrane level.