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Effect of dietary iron loading on recognition memory in growing rats.

Han M, Kim J - PLoS ONE (2015)

Bottom Line: While nutritional and neurobehavioral problems are associated with both iron deficiency during growth and overload in the elderly, the effect of iron loading in growing ages on neurobehavioral performance has not been fully explored.These results support the idea that iron is essential for learning and memory and further reveal that iron supplementation during developmental and rapidly growing periods of life improves memory performance.Our investigation also demonstrates that both cholinergic and glutamatergic neurotransmission pathways are regulated by dietary iron and provides a molecular basis for the role of iron loading in improved memory.

View Article: PubMed Central - PubMed

Affiliation: Department of Pharmaceutical Sciences, Northeastern University, Boston, Massachusetts, United States of America.

ABSTRACT
While nutritional and neurobehavioral problems are associated with both iron deficiency during growth and overload in the elderly, the effect of iron loading in growing ages on neurobehavioral performance has not been fully explored. To characterize the role of dietary iron loading in memory function in the young, weanling rats were fed iron-loading diet (10,000 mg iron/kg diet) or iron-adequate control diet (50 mg/kg) for one month, during which a battery of behavioral tests were conducted. Iron-loaded rats displayed elevated non-heme iron levels in serum and liver, indicating a condition of systemic iron overload. In the brain, non-heme iron was elevated in the prefrontal cortex of iron-loaded rats compared with controls, whereas there was no difference in iron content in other brain regions between the two diet groups. While iron loading did not alter motor coordination or anxiety-like behavior, iron-loaded rats exhibited a better recognition memory, as represented by an increased novel object recognition index (22% increase from the reference value) than control rats (12% increase; P=0.047). Western blot analysis showed an up-regulation of dopamine receptor 1 in the prefrontal cortex from iron-loaded rats (142% increase; P=0.002). Furthermore, levels of glutamate receptors (both NMDA and AMPA) and nicotinic acetylcholine receptor (nAChR) were significantly elevated in the prefrontal cortex of iron-loaded rats (62% increase in NR1; 70% increase in Glu1A; 115% increase in nAChR). Dietary iron loading also increased the expression of NMDA receptors and nAChR in the hippocampus. These results support the idea that iron is essential for learning and memory and further reveal that iron supplementation during developmental and rapidly growing periods of life improves memory performance. Our investigation also demonstrates that both cholinergic and glutamatergic neurotransmission pathways are regulated by dietary iron and provides a molecular basis for the role of iron loading in improved memory.

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Effect of dietary iron loading on recognition memory in growing rats.Rats fed iron-loading or control diet were subject to the novel object recognition task in an open field where two identical objects were placed. Rat behavior was recorded for 5 min and time of interaction with each object was recorded to quantify recognition index during the training period (A). Following 2 h of training with two identical objects, one object was replaced with a different object and time of interaction with each object was recorded to calculate % recognition index (= interaction time with the novel object divided by interaction time with both novel and familiar objects) (A). Total velocity traveled in the field was also recorded (B). The dotted line represents a reference baseline of 50% random chance. Empty and closed bars represent control (Con) and iron-loaded (IL) rats, respectively. Data were presented as means ± SEM (n = 11 per group) and were analyzed using two-sample t-test. * P < 0.05.
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pone.0120609.g003: Effect of dietary iron loading on recognition memory in growing rats.Rats fed iron-loading or control diet were subject to the novel object recognition task in an open field where two identical objects were placed. Rat behavior was recorded for 5 min and time of interaction with each object was recorded to quantify recognition index during the training period (A). Following 2 h of training with two identical objects, one object was replaced with a different object and time of interaction with each object was recorded to calculate % recognition index (= interaction time with the novel object divided by interaction time with both novel and familiar objects) (A). Total velocity traveled in the field was also recorded (B). The dotted line represents a reference baseline of 50% random chance. Empty and closed bars represent control (Con) and iron-loaded (IL) rats, respectively. Data were presented as means ± SEM (n = 11 per group) and were analyzed using two-sample t-test. * P < 0.05.

Mentions: To evaluate if iron loading influences memory capacity in growing rats, rats fed either high iron or control diet were tested for the novel recognition memory task. During the training session, both control and iron-loaded rats spent similar time in recognizing two identical objects, indicating there was no preference for object location (Fig. 3A). When one of the familiar objects was replaced by a novel object 2 h after the training session, control rats recognized the novel object (61.7%) better than the familiar object (38.3%). Notably, the percent time spent with the novel object increased significantly in iron-loaded rats (72.4%) compared with the familiar object (27.6%). When assessed against 50% random chance, recognition index was significantly increased in iron-loaded rats compared with controls (22.4 vs 11.7% from the reference baseline of 50%; P = 0.047; n = 11/group; Fig. 3A), indicating an improved recognition memory upon iron loading in growing rats. Overall velocity in the open field was not altered in iron-loaded rats (Fig. 3B), suggesting that the difference in recognition memory was not due to altered exploratory behavior during the test.


Effect of dietary iron loading on recognition memory in growing rats.

Han M, Kim J - PLoS ONE (2015)

Effect of dietary iron loading on recognition memory in growing rats.Rats fed iron-loading or control diet were subject to the novel object recognition task in an open field where two identical objects were placed. Rat behavior was recorded for 5 min and time of interaction with each object was recorded to quantify recognition index during the training period (A). Following 2 h of training with two identical objects, one object was replaced with a different object and time of interaction with each object was recorded to calculate % recognition index (= interaction time with the novel object divided by interaction time with both novel and familiar objects) (A). Total velocity traveled in the field was also recorded (B). The dotted line represents a reference baseline of 50% random chance. Empty and closed bars represent control (Con) and iron-loaded (IL) rats, respectively. Data were presented as means ± SEM (n = 11 per group) and were analyzed using two-sample t-test. * P < 0.05.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4352024&req=5

pone.0120609.g003: Effect of dietary iron loading on recognition memory in growing rats.Rats fed iron-loading or control diet were subject to the novel object recognition task in an open field where two identical objects were placed. Rat behavior was recorded for 5 min and time of interaction with each object was recorded to quantify recognition index during the training period (A). Following 2 h of training with two identical objects, one object was replaced with a different object and time of interaction with each object was recorded to calculate % recognition index (= interaction time with the novel object divided by interaction time with both novel and familiar objects) (A). Total velocity traveled in the field was also recorded (B). The dotted line represents a reference baseline of 50% random chance. Empty and closed bars represent control (Con) and iron-loaded (IL) rats, respectively. Data were presented as means ± SEM (n = 11 per group) and were analyzed using two-sample t-test. * P < 0.05.
Mentions: To evaluate if iron loading influences memory capacity in growing rats, rats fed either high iron or control diet were tested for the novel recognition memory task. During the training session, both control and iron-loaded rats spent similar time in recognizing two identical objects, indicating there was no preference for object location (Fig. 3A). When one of the familiar objects was replaced by a novel object 2 h after the training session, control rats recognized the novel object (61.7%) better than the familiar object (38.3%). Notably, the percent time spent with the novel object increased significantly in iron-loaded rats (72.4%) compared with the familiar object (27.6%). When assessed against 50% random chance, recognition index was significantly increased in iron-loaded rats compared with controls (22.4 vs 11.7% from the reference baseline of 50%; P = 0.047; n = 11/group; Fig. 3A), indicating an improved recognition memory upon iron loading in growing rats. Overall velocity in the open field was not altered in iron-loaded rats (Fig. 3B), suggesting that the difference in recognition memory was not due to altered exploratory behavior during the test.

Bottom Line: While nutritional and neurobehavioral problems are associated with both iron deficiency during growth and overload in the elderly, the effect of iron loading in growing ages on neurobehavioral performance has not been fully explored.These results support the idea that iron is essential for learning and memory and further reveal that iron supplementation during developmental and rapidly growing periods of life improves memory performance.Our investigation also demonstrates that both cholinergic and glutamatergic neurotransmission pathways are regulated by dietary iron and provides a molecular basis for the role of iron loading in improved memory.

View Article: PubMed Central - PubMed

Affiliation: Department of Pharmaceutical Sciences, Northeastern University, Boston, Massachusetts, United States of America.

ABSTRACT
While nutritional and neurobehavioral problems are associated with both iron deficiency during growth and overload in the elderly, the effect of iron loading in growing ages on neurobehavioral performance has not been fully explored. To characterize the role of dietary iron loading in memory function in the young, weanling rats were fed iron-loading diet (10,000 mg iron/kg diet) or iron-adequate control diet (50 mg/kg) for one month, during which a battery of behavioral tests were conducted. Iron-loaded rats displayed elevated non-heme iron levels in serum and liver, indicating a condition of systemic iron overload. In the brain, non-heme iron was elevated in the prefrontal cortex of iron-loaded rats compared with controls, whereas there was no difference in iron content in other brain regions between the two diet groups. While iron loading did not alter motor coordination or anxiety-like behavior, iron-loaded rats exhibited a better recognition memory, as represented by an increased novel object recognition index (22% increase from the reference value) than control rats (12% increase; P=0.047). Western blot analysis showed an up-regulation of dopamine receptor 1 in the prefrontal cortex from iron-loaded rats (142% increase; P=0.002). Furthermore, levels of glutamate receptors (both NMDA and AMPA) and nicotinic acetylcholine receptor (nAChR) were significantly elevated in the prefrontal cortex of iron-loaded rats (62% increase in NR1; 70% increase in Glu1A; 115% increase in nAChR). Dietary iron loading also increased the expression of NMDA receptors and nAChR in the hippocampus. These results support the idea that iron is essential for learning and memory and further reveal that iron supplementation during developmental and rapidly growing periods of life improves memory performance. Our investigation also demonstrates that both cholinergic and glutamatergic neurotransmission pathways are regulated by dietary iron and provides a molecular basis for the role of iron loading in improved memory.

Show MeSH
Related in: MedlinePlus