Olfactory function in zinc-deficient adult mice

Adult zinc deficiency reportedly leads to degeneration of the olfactory epithelium in the rat. Human zinc deficiency can cause reduced olfactory sensitivity. Given the importance of zinc in embryonic neural development its primary action on the adult olfactory system may be to disrupt olfactory receptor neurogenesis. We report here on the effects of zinc deficiency on the olfactory system of the adult mouse. After 42 days of dietary restriction of zinc, mice were tested behaviourally for olfactory function and general activity. Their olfactory epithelia were examined histologically using [3H]-thymidine autoradiography to identify recently-divided cells, and immunohistochemistry for olfactory marker protein to identify mature receptor neurones. Zinc deficient mice failed to show a food odour preference but they were as active as controls and their olfactory epithelia appeared normal. Basal cell proliferation and post-mitotic survival were similar to controls and the epithelia were of normal thickness and were positive for olfactory marker protein. It was concluded that zinc deficiency did not affect the turnover of cells in the olfactory epithelium. It may disrupt olfactory function through interference with zinc-containing neurones in higher olfactory centres.