- Release of Zn2+ from presynaptic glutamatergic terminals has long been considered the principle challenge necessitating the existence of zinc homeostatic proteins (ZHP) in the mammalian nervous system. It is now known that neural cells also possess an intracellular zinc pool, termed here [Zn2+]i, which functions in a cell signaling context. A major challenge is characterizing the interaction of these two populations of zinc ions. To assess the relationship of this Zn2+ pool to cellular ZHP production, we employed immunofluorescence and immunoblot analysis to compare the expression of ZHP's ZnT-1 and MT-I/II in olfactory bulb and hippocampus of wild-type and ZnT-3 KO mice, which lack synaptic Zn2+. In both areas, the respective distribution and concentration of ZnT-1 and MT-I/II were identical in ZnT-3 KO and control animals. We subsequently examined ZHP content in ZnT-3 KO and WT mice treated with a membrane-permeable Zn2+ chelator. In both olfactory bulb and hippocampus of the KO mice, the ZHP content was significantly reduced 15 h after chelation of [Zn2+]i compared to WT controls. Our findings support the conclusion that ZHP expression is regulated by crosstalk between synaptic and intracellular pools of Zn2+. J. Cell. Physiol. 224: 567–574, 2010. © 2010 Wiley-Liss, Inc.