Change of zinc distribution in rat brain with increasing age.

Zinc (Zn) accumulation in the brain of rats of various ages was studied to look into the significance of Zn for the development and function of the brain. The Zn concentration of the cerebral hemisphere was relatively low in 1- to 11-day-old rats. The Zn concentration of the cerebellum gradually increased after birth and reached nearly a plateau at 11 days old. At 48 weeks old, the Zn concentrations of the cerebral cortex and hippocampus formation were approximately twice that of the cerebral hemisphere at the early stage after birth and significantly higher than that of the cerebellum. When 65ZnCl2 was injected into two groups of rats at 5 days and 48 weeks old for comparison, 65Zn distribution in the brain of the former group was higher than that of the latter. In the neonatal rats, the highest concentration of 65Zn was found in the cerebellum, followed by the hippocampus formation, a Zn-containing neuron-rich region. In the adult rats, the highest concentration of 65Zn was found in the CA3 and dentate gyrus of the hippocampus formation. At 48 weeks, 65Zn distribution in the cerebellum was relatively low and at about the same level as in the cerebral cortex. These results suggest that Zn is highly demanded by the cerebellum, which develops rapidly after birth. The increase in Zn concentration with increasing age may reflect the Zn requirement for functioning as an neuromodulator as well as for brain development.