Variations in trace metal levels in rat hippocampus during ontogenetic development.

The variations in trace metal (zinc, iron, copper and manganese) levels in rat hippocampus were followed by atomic absorption spectrophotometry from the 17th embryonic day to the 100th postnatal day. In agreement with histochemical observations, it was found that the greatest relative increase in the hippocampal zinc level occurs during the 11th-20th postnatal days, simultaneously with the morphological maturation of the mossy fibre terminals. The iron level falls dramatically from the 17th embryonic day to the 3rd postnatal day. Beginning from the 11th postnatal day, the iron level, similarly to the copper level, continuously increases with age. The manganese level rises up to the 20th postnatal day, and subsequently progressively decreases. It is suggested that all of these elements are indispensable for the normal development and functioning of the hippocampus and the mossy fibre terminals.