Comparative Developmental Studies on the Fine Structure of the Vomeronasal Sensory and the Olfactory Epithelia in the Golden Hamster

Chronological development of the vomeronasal sensory and the olfactory epithelia was comparatively examined by light and electron microscopy. Both epithelia were divergently derived from the olfactory placode and had common stem cells. In the olfactory epithelium, stem cells were rapidly differentiated into olfactory cells or supporting cells, coming to possess almost the same cytological features as in the adult at 1 day after birth. In the vomeronasal sensory epithelium, stem cells were slowly differentiated into sensory cells or supporting cells, retaining some immature properties even at 10 days after birth. Some characteristics were observed in appearance and development of various organelles in both the epithelia. Free ribosomes and mitochondria were observed from the earliest stage of development, since they were essential for the metabolism of stem cells. Centrioles were observed in receptor cells of these epithelia. In the olfactory cells cilia were developed, but in the vomeronasal sensory cells they were absent all life of the cells. Centrioles may be interpreted as sites of nucleation of microtubules in receptor cells. According to the foregoing observations, it seems that the olfactory function is mainly ascribed to the olfactory epithelium and that the vomeronasal sensory epithelium participates in olfaction by enhancing and supplementing the discriminative activity of the olfactory epithelium and/or is engaged in unknown sensations different from olfaction.