Does intranasal application of zinc sulfate produce anosmia in mouse? An olfactometric and anatomical study

Mice pre-trained in an olfactometer were tested daily on odor detection and discrimination tasks after irrigation of their olfac- tory epithelium in each naris with 50 μl of 5% zinc sulfate or saline. Anterograde transport of a wheatgerm agglutinin–horse- radish peroxidase (WGA-HRP) conjugate from the epithelium to the olfactory bulb was used to assess anatomical connectivity in these and in mice that were used only for histological analyses. One day after treatment, saline controls performed at high levels of accuracy in detecting vapor from solutions of 5–0.01% ethyl acetate and in an odor discrimination task but most ZnSO4-treated mice performed at chance for 5–30 days before showing recovery. Although dense WGA-HRP reaction product was found in the accessory olfactory bulb, there was little or no evidence for axonal transport to glomeruli of the main olfactory bulb in the first 4–8 days after treatment. These results demonstrate that intranasal application of ZnSO4 to mice produces a brief but essentially total disruption of functional connections from the olfactory epithelium to the main olfactory bulb and a corresponding transient anosmia.