Stimulation-induced uptake and release of zinc in hippocampal slices

Abstract

The mossy-fibre axons of the hippocampus form a dense plexus, uniquely rich in chelatable zinc^1–3. Because the metal is apparently concentrated within the terminal bags of the axons^4,5, it has been hypothesized that the zinc is involved in mossy-fibre synaptic transmission^6,7. Although some electrophysiological findings^8,9 have favoured the hypothesis, neither preferential uptake of zinc into the hippocampus^10,11 nor depolarization-induced release of zinc from hippocampal tissue¹² has previously been found. Using the hippocampal slice preparation, we now report that the mossy-fibre neuropil and cells of origin (dentate granule cells) take up zinc preferentially, and that electrical stimulation selectively facilitates both uptake of exogenous zinc into mossy-fibre neuropil and release of previously incorporated ⁶⁵Zn from the tissue. The results suggest that the role of zinc in mossy-fibre axons is dynamically linked to neural signalling processes.