Movement of zinc and its functional significance in the brain.

Zinc, an essential nutrient, is supplied to the brain via both the blood-brain and blood-cerebrospinal fluid barriers. Zinc is most concentrated in the limbic system, i.e. the hippocampus and amygdala, zinc-containing glutaminergic neuron-rich areas. A large portion of zinc serves the function of zinc metalloproteins in neurons and glial cells. In zinc-containing glutaminergic neurons, vesicular zinc, probably ionic zinc, may serve as an endogenous neuromodulator in synaptic neurotransmission. Vesicular zinc is dynamically coupled to the electrophysiological activity of zinc-containing glutaminergic neurons. Dietary zinc deprivation may influence zinc homeostasis in the brain, resulting in brain dysfunction such as learning impairment. Excessive excitation of zinc-containing glutaminergic neurons causes a decrease in vesicular zinc, and the decrease might be associated with the susceptibility to seizure. Alteration of zinc levels released into the synaptic cleft may influence neurotransmission in zinc-containing glutaminergic synapses. Therefore, zinc homeostasis in the presynaptic vesicle is important for the function of zinc-containing glutaminergic neurons.