AIM: To investigate the effect of deafferentation on the expression level of calretinin (CR) in adult Sprague Dawley rat olfactory bulb (OB). METHODS: Adult Sprague Dawley rats were given a single intranasal irrigation with ZnSO_4. A specific period (10, 20, 30 and 60 days, respectively) after the treatment, immunoreactivities of tyrosine hydroxylase (TH) and calretinin of OB were examined by using immunohistochemistry. Down-regulation of TH expression level was regarded as a mark of deafferentation. RESULTS: 10, 20, 30 and 60 days after ZnSO_4 treatment, staining intensity and density of TH-immunoreactive cells of OB significantly reduced and the degree of reduction was correlated with the time of treatment before 30 days, but the result of 60 d was similar to that of 30 d. There was no obvious change in the density of CR-immunopositive cells after the same treatment. CONCLUSION: Expression of CR in adult rat OB was not affected by deafferentation.