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.

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.

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.

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.

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.

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.

Decline of maternal behavior in the virgin and lactating rat.

Sensitized virgins and postpartum lactating mothers, both exhibiting maternal behavior, were given donor litters that increased in age by 1 day, for 28 days, starting at the onset of maternal behavior. Each day females were tested for maternal behavior with pups 4-8 days old: Maternal care (i.e., nursing/crouching, retrieving, nest building and licking) and maternal withdrawal, rejection, and prevention of nursing were recorded. After the ninth day, females were also tested with the progressively older pups from 10 to 28 days of age with which they were living. Virgins and lactating mothers showed generally similar patterns of maternal care although some differences were found, and they declined in maternal behavior toward the older pups in a similar manner. Maternal behavior did not decline in tests with younger pups. The results are interpreted as supporting the hypothesis that the decline as well as the maintenance of maternal behavior postpartum is nonhormonally mediated.