Recently, the function of zinc in the axonal boutons of hippocampal neurons has come under increased scrutiny as evidence has emerged of a putative role for this metal ion in neural damage following insults such as ischemia, blunt force trauma, and seizure. Indeed, the nonpathological role of free zinc in the brain remains cryptic after more than 40 years. We have used a biosensing approach to determine free zinc ion concentrations by fluorescence lifetime, intensity, intensity ratio, or anisotropy changes caused by binding of zinc to variants of a protein, apocarbonic anhydrase II (apo-CA). This approach permits real time measurement of zinc down to picomolar levels, with no perceptible interference from other divalent metal ions abundant in serum and tissue, such as calcium and magnesium. Recently, we used apo-CA together with a fluorescent ligand whose binding is metal-dependent to obtain the first fluorescence micrographs of zinc release from a rat hippocampus model in response to electrical stimulus. In our view, elucidation of the zinc fluxes in neural tissue ultimately requires quantitation, as in the case of calcium. Recent results will be shown.