Sydney Reisbick

Home cage behavior of rhesus monkeys with long-term deficiency of omega-3 fatty acids

In an observational study with a blind observer, rhesus monkeys deficient in omega-3 (omega-3 or n-3) fatty acids initiated more bouts of stereotyped behavior in their home cages than monkeys fed a matched control diet abundant in omega-3 fatty acids. Locomotion bouts were also more frequent in deficient monkeys, but nonstereotyped locomotion did not differ. Both stereotyped behavior and the sum of all behavioral bouts were more frequent in 4-5-year-old than in 2-3-year-old monkeys, and stereotype decreased after meals in males but not females. The stereotyped behaviors associated with a deficit in omega-3 fatty acids were those typical of rhesus monkeys raised as partial social isolates or those whose surroundings have been disrupted.

The role of n-3 fatty acids in visual and cognitive development; Current evidence and methods of assessment

Low levels of dietary n-3 fatty acids during development lead to changes in the electroretinogram and visual acuity in rats, monkeys, and human infants. Additional aspects of vision can be measured in infants and may provide further useful information about the nature of the changes induced by n-3 fatty acid deficiency and their potential long-term relevance for formula-fed human infants. Several tests are available to assess the development of specific cognitive functions such as visual recognition and short-term memory. These measures can provide information that is not now available to test the hypothesis that n-3 fatty acids are important for other aspects of neural function, including intellectual or cognitive development.

Visual attention in infant monkeys: effects of dietary fatty acids and age.

Effects of dietary essential fatty acids on visual attention were explored longitudinally in infant rhesus monkeys with a visual paired-comparison paradigm. Sets of primate faces and of patterns were presented at Weeks 2, 5, 9, and 13 to 9 infants deficient in omega-3 fatty acids and 8 fed a standard nursery diet. Familiarization to 1 member of each pair preceded simultaneous presentation of both stimuli. Infants fed the deficient diet showed longer individual looks in both immediate and 24-hr tests. Duration of looks decreased with age to familiar but not to novel stimuli. The proportion of time looking at the novel stimulus (% novel) increased with age but was not affected by diet. Look duration and % novel were differentially affected and may reflect different underlying processes.

Polydipsia in rhesus monkeys deficient in omega-3 fatty acids☆

Omega-3 fatty acids are a major component of neural membranes. They are essential nutrients for normal biochemical development of the brain and retina and may affect behavior. In our studies of long-term dietary omega-3 fatty acid deficiency, we have found a new effect of this deficiency in rhesus monkeys. Deficient monkeys visited the home cage drinking spout more frequently than controls (Experiment 1), and drank more water over 24 hours (Experiment 2). The increase in intake was mirrored by increased combined output of urine + feces over 24 hours (Experiment 3), and was not due to spillage (Experiment 4). The dietary deficiency greatly reduced omega-3 fatty acids in red blood cells but did not affect serum electrolyte levels. The changes in fluid intake and output may be related to direct or indirect effects on central or peripheral control mechanisms for drinking or excretion, which may be mediated by altered composition of neural or other membranes or changes in eicosanoid metabolism.

Postnatal deficiency of omega-3 fatty acids in monkeys: fluid intake and urine concentration.

Previous studies demonstrated increased fluid intake in rhesus monkeys exposed to combined prenatal and long-term postnatal (PRE+POST) dietary deficiency of omega-3 fatty acids. Here we determined the effect of dietary deficiency in omega-3 fatty acids occurring only prenatally (PRE) or only postnatally (POST). Water intake over 24 hours, water intake in 15-minute tests, and excretion of combined urine and feces over 24 hours were all about twice as great in POST as in PRE monkeys. Neither group preferred or avoided salt solutions compared to water in two-bottle tests. Serum electrolytes, total protein, and glucose were within the normal range, and both groups concentrated urine when deprived of water. Levels of all omega-3 fatty acids in red blood cells were greatly depressed in POST monkeys, while levels of omega-6 fatty acids were elevated or unchanged. These results confirm the effects of PRE+POST deficiency on fluid intake and demonstrate that postnatal deficiency by itself is sufficient for the effects.

Omega-3 Fatty Acid Deficiency and Behavior

Much of the impetus for studies of omega-3 fatty acid (FA) deficiency originates from the need to determine whether these FA should be added to human infant formulas, and if so in what form: as the precursor omega-3 FA, linolenic acid (18:3 omega-3, or as the derived form, docosahexaenoic acid ([DHA], 22:6 omega-3), which is present at high levels in retina and brain. After early studies showed effects of omega-3 FA deficiency on visual development in monkeys (Neuringer et al., 1984, 1986), levels of linolenic acid were increased in many infant formulas, especially those in the United States, beginning in 1987. However, DHA levels in erythrocytes of human infants fed formulas with either low or high levels of linolenic acid were lower than the DHA levels of infants who received DHA directly either in breast milk or in fish oil supplemented formulas (Pita et al., 1988; Carlson et al., 1986; Makrides et al., 1993; Uauy et al., 1994). This finding suggested that human infants do not elongate and desp.turate an adequate amount of linolenic acid into DHA. This hypothesis was supported by more recent postmortem studies that reported lower DHA levels in the cerebral cortex of infants fed formulas with linolenic acid than in breast-fed infants (Farquharson et al., 1992; Makrides et al., 1994).

Increased intake of water and NaCl solutions in omega-3 fatty acid deficient monkeys

We previously reported that long-term omega-3 fatty acid deficiency is associated with increased water intake in rhesus monkeys. To determine whether the increase was specific to water, intakes of salt solutions were measured in 15-minute single-bottle tests. Deficient monkeys drank at least twice as much of all NaCl concentrations as controls. Overall intake decreased as salt concentration increased. In 2-bottle preference tests, deficient monkeys again drank more total fluid but neither preferred nor avoided normal saline compared to controls. When deprived of water, deficient monkeys concentrated urine as well as controls, demonstrating that the increased intake was not a result of renal failure or diabetes insipidus. Omega-3 fatty acids have roles both in neural membrane function and in metabolism of prostaglandins and other eicosanoids. Omega-3 fatty acid deficiency may affect drinking through changes in one or both of these functions.

Visual recognition memory in infant rhesus monkeys: Effects of dietary taurine☆

Abstract The effects of dietary taurine on visual recognition memory and visual attention were measured with visual paired comparison tests in infant rhesus monkeys. Infants (6 per group) were fed one of two human infant soy-protein formulas: taurine-free (-T) or taurine-supplemented (+T). The infants were tested at 2.0, 3.5, 5.0, and 9.0 weeks of age using eight pairs of patterns and eight pairs of photographs of primate faces. The -T infants had higher novelty preference for faces, higher total looks at faces and patterns at 2 weeks and at patterns at 9 weeks, and a higher number and proportion of shifts between pattern stimuli at 9 weeks. They also showed increased attention, as estimated by the total time looking during the tests at 2 weeks and decreased time to reach a criterion of 10 s of fixation during familiarization at 9 weeks. Thus, contrary to expectation, -T infants had higher scores on several measures associated with more advanced cognitive functioning.