AL Rats Research Articles

Learning and memory impairment in adult rats due to severe zinc deficiency during lactation

In a series of three experiments, adult rats who suffered severe zinc deficiency and/or undernutrition during lactation were tested in a 17-arm radial maze for working memory, reference memory, forgetting and learning. In Experiment 1, eight out of 17 arms were baited. The zinc deficient (ZD) and undernourished (PF) rats revealed a learning deficit when compared to adequately nourished rats (AL). ZD rats also appeared to display a loss of working memory. No evidence of loss of reference memory was observed among any of the groups. A reverse learning procedure was used in Experiment 2 to test the same rats used in Experiment 1. ZD rats were significantly inferior in performance of the reverse learning task compared to the AL and PF rats. No significant differences in performance were noted between the AL and PF rats. Although all groups displayed forgetfulness from Experiment 1 to Experiment 2, no significant differences in forgetfulness were evidenced among the groups. In Experiment 3, all 17 arms were baited. The ZD rats displayed a significant working memory deficit as compared to the AL and PF rats. No significant differences in working memory between the AL and PF rats occurred. The possibility that the differences in performance were due to differences in food motivation or attention was considered and rejected. It was concluded that ZD rats experienced a severe learning deficit and some working memory deficit while the PF rats experienced a mild learning deficit as compared to the AL rats.

Effect of zinc deficiency on appetite and plasma amino acid concentrations in the rat.

1. Levels of zinc in liver and plasma of the Zn-depleted rats fluctuated with the feeding cycle and were significantly higher at the bottom than at the top of the cycle. As Zn deficiency became more severe fluctuations in plasma Zn diminished. Concentrations of Zn in liver, in contrast to levels in plasma and femur, were not markedly lowered by day 15. 2. In contrast to ad lib-fed (AL) and overnight-fasted (OF) controls, some pair-fed (PF) controls had elevated levels of Zn in liver and plasma. 3. Intakes of water and food were significantly correlated in Zn-deficient rats. Packed cell volumes were significantly higher for Zn-depleted than for AL and PF rats. 4. Food intakes and plasma glucose concentrations were related in AL, OF and PF control rats but not in Zn-deficient rats. 5. At day 15 of Zn deficiency the order of total plasma amino acid concentrations in the groups of rats was AL greater than Zn-deficient greater than OF greater than PF. Many of the differences between the AL and OF groups for individual plasma amino acids also appeared in the Zn-deficient group at the top and bottom of the feeding cycle. Differences in individual amino acid concentrations at the top and bottom of the feeding cycle tended to be opposite in the PF and the Zn-deficient group. Levels of tyrosine and tryptophan in plasma were correlated (P less than 0.05) with the cyclic feeding pattern of the Zn-deficient group; however, the ratios tryptophan or tyrosine: sum of other large neutral amino acids did not correlate significantly with the eating habits of Zn-deficient rats.

636 NEUTROPHIL MIGRATION DEFECT DURING EXPERIMENTAL NUTRITIONAL IRON DEFICIENCY IN POST-WEANING RATS

The study of neutrophil (PMN) functions in children with iron deficiency (ID) has yielded controversial results, partly because of the uncontrollable association of other nutritional deficiencies with that condition. We have studied the effect of isolated iron deficiency on in vivo PMN migration in six rats fed an iron-poor diet until 70 days post-weaning. The same diet was fed to 12 control animals, either as paired feedings (PF) or ad libitum feedings (AL); these controls were made iron sufficient with intramuscular iron dextran at weaning. Seventy days post-weaning weights (mean ± SE, in g) were essentially identical in ID (205 ± 13), PF (188 ± 6), and AL (225 ± 15) rats. Anemia was evident in ID rats (Hb. 9.7 ± 0.7 g/dl, MCV 47 ± 1.5 fl.) but not present in PF or AL controls (Hb. 17 ± 1.7 and 14.9 ± 0.3, MCV 54 ± 1.3 and 57 ± 1.3 respectively). PMN migration into the peritoneal cavity was induced by 18-hour stimulation with Na caseinate and expressed as total numbers of PMNS × 105/100 g body weight. PMN migration was significantly lower in ID animals (49.3 ± 6.2) than in PF (125 ± 28) and AL (111 ± 18) animals (P < 0.025). In post-weaning rats, isolated iron deficiency is associated with the development of a pronounced decrease in PMN migration, in vivo. This decrease might contribute to the increased tendency toward infections observed in some ID subjects.