Nature Chem. Biol. doi:10.1038/nchembio.146 (2009)

Zinc activates an ion channel that also responds to pungent foods such as wasabi and cinnamon, possibly explaining why zinc overexposure causes pain and inflammation.

When ions flow through the TRPA1 channel, pain neurons fire. Ardem Patapoutian at the Genomics Institute of the Novartis Research Foundation in San Diego, California, and his colleagues report that 15% of mouse sensory neurons show increased activity when exposed to zinc, and that mouse neurons lacking TRPA1 are unaffected by the element. Mice without a working version of the gene that encodes TRPA1 displayed fewer signs of discomfort when injected with zinc acetate.

'Inside out' cell membranes were highly sensitive to zinc, suggesting that it activates TRPA1 from inside neurons.