Signaling by Synaptic Zinc is Required for Whisker-Mediated, Fine Texture Discrimination.

Zinc-containing terminals are found throughout the neocortex, concentrated predominantly in layers II/III, V, and VI. Synaptic zinc is a potent neurotransmitter/modulator and, therefore, may mediate inter- or intra-cortical integration of sensory information. We have previously shown that levels of synaptic zinc are rapidly modulated in somatosensory (barrel) cortex, in an experience- and activity-dependent manner. Zinc transporter 3 (ZnT3) knockout (KO) mice lack synaptic zinc and provide us with a good model to examine the contribution of synaptic zinc to barrel cortex-dependent behavior. In the present study, we show that ZnT3 KO mice display a marked decrease in acuity for whisker-dependent texture discrimination. ZnT3 KO mice were not able to discriminate between textures having an average particle diameter less than 300 μm while control mice were able to discriminate between textures having particle diameters separated by as little as 25 μm. This loss of texture discrimination acuity in ZnT3 KO mice was whisker-dependent and was observed in young (2 months-of-age) and older mice (12 months-of-age). These results show that zincergic signaling is necessary for the normal integration of somatosensory information.