〈Originals〉Application of layer-specific markers in the evaluation of abnormal cytoarchitecture in the olfactory bulb of prokineticin receptor 2 deficient mice

Prokineticin receptor 2 gene mutant mice (Pkr2-1-) show deformity in the olfactory bulb (OB), they lose axonal invasion from the olfactory sensory neurons and olfactory interneurons fail to migrate in the OB. In the present study, we examined whether the mutant has an abnormality in the laminar structure in the OB by HE staining and immunohistochemistry using antityrosine hydroxylase (TH), parvalbumin (PV), and reelin (RE) with special reference to the layered structure. In Pkr2-1mice, TH-immunoreactive neurons were localized in the marginal area of the OB and the number and size of TH-expressing cells were markedly decreased. The distribution of PV-immunoreactive cells showed no apparent difference but the cells were significantly smaller in the mutant is wild-type mice (WT). RE-immunoreactive mitral cells showed abnormal alignment, the direction of neurite outgrowth was not well coordinated and they were much smaller than those in WT mice. The present findings suggest that not only the impairment of neuronal migration but also the loss of afferent axonal projection from the olfactory epithelium to the OB arrested the maturation and induced apoptosis of PV-, TH-, and RE-immunoreactive neurons in Pkr2-1-.