〈Originals〉Profile of tyrosine hydroxylase-expressing neurons in the olfactory bulb of prokineticin type 2 receptor-deficient mice during embryonic development

Abstract

[Abstract]　Dopamine neurons in the olfactory bulb play essential roles in the maintenance of olfactory function. The maturation of these neurons involves mitosis, cell migration and the transcriptional regulation of specific neurotransmitters and is an intensively studied process. In our present study, we investigated the embryonic development of tyrosine-hydroxylase (TH)-expressing neurons in the main olfactory bulb (MOB) of Pkr2^ mice that lack axonal infiltration from the olfactory neurons (ON) and wild-type littermates (WT) at E16.5, E18.5 and P0 using immunohistochemical techniques. Even at E16.5, we observed two populations of neurons in the MOB of WT mice, one scattered in the primitive glomerular layer and another population of TH-positive neurons in the surface region of the primitive granular cell layer. The number of TH-positive neurons had increased markedly by P0. Pkr2^ mouse embryos and neonates showed disorganization of the layered structure, mainly due to the loss of glomerular layer in the olfactory system. The number of TH-immunoreactive cells per slice was markedly lower at P0 but not at E16.5 and E18.5. Interestingly, even in Pkr2^ mice, TH-immunoreactive neurons were still present in the periphery of the MOB. Hence, it is highly probable that the lack of Pkr2-i- does not affect the migration of TH-containing neurons from the subventricular zone to the periphery of the MOB during embryonic development but strongly impairs the migration of TH-expressing neurons or TH expression in the MOB around birth.Masumoto, Koh-he