Brain iron: a lesson from animal models.

Brain and blood iron deficiency (ID) can be nutritionally induced. Significant behavioral and brain-biochemical changes are observed in rats rendered iron deficient, including complete reversal of the circadian cycles of motor activity, changes in thermoregulation and stereotyped behavior, and an increased pain threshold. The increase in pain threshold is affected by diurnal factors and peripheral treatment with beta-endorphin has a significant analgesic effect, implicating selective changes in the blood-brain barrier. These effects along with modifications in responses to dopaminergic drugs, interactions of ID with neuroleptic drugs, and modifications in behavior as a result of selective brain lesions, lead to two conclusions: this animal model is appropriate for human anemia and the best explanation for the variety of behavioral and brain biochemical changes in ID rats is that the principal effect of brain ID is a selective decrease in the functional level of the dopaminergic D2 system.