Alteration of carnosine expression in olfactory system of mouse after unilateral naris closure and partial bulbectomy

To investigate the function of the dipeptide carnosine in the olfactory system, alterations of carnosine in the primary olfactory nerve after unilateral naris closure or olfactory bulb semilesion were studied by means of immunocytochemistry. After unilateral naris closure, carnosine staining showed no alteration, but immunoreactivity of tyrosine hydroxylase (TH), the rate-limiting enzyme for biosynthesis of dopamine in dopaminergic neurons, decreased dramatically in periglomerular neurons. This behavior of carnosine is consistent with that reported for the olfactory marker protein (OMP). On the other hand, following partial lesion of the olfactory bulb, ordinary to strong carnosine expression was seen in newly innervated glomeruli that exceeded that seen in the conventional targets. Ectopic, TH-positive, periglomerular cell-like neurons appeared around the newly formed glomeruli. These data suggest that carnosine may have some role in regulating TH expression in post-synaptic neurons.