Imaging Zinc in Brain Slices

INTRODUCTION

This protocol provides a practical guide to imaging zinc within synaptic vesicles and the extracellular space of brain slices. Certain glutamatergic synaptic terminals in the brain have high concentrations of exchangeable Zn²⁺ within their synaptic vesicles. Classically, these terminals have been revealed by Timm’s histochemical stain. More recently, a number of fluorimetric probes have become available that allow Zn²⁺ to be detected in live preparations. This protocol describes two methods, one for visualizing Zn²⁺ in synaptic vesicles, and another for detecting Zn²⁺ in the extracellular space. These methods are applicable to any tissue with the high levels of loosely bound Zn²⁺ that are typically found in vesicles, and tissue that might have Zn²⁺ associated with macromolecules in the extracellular space.