Proliferation and migration of receptor neurons in the vomeronasal organ of the adult mouse.

Cell proliferation and differentiation in the vomeronasal organ of the adult mouse was studied by bromodeoxyuridine (BrdU) immunohistochemistry coupled to immunostaining for specific markers of the differentiation, such as carnosine, B50-GAP43 (growth-associated protein) and stathmin. The present study shows that three populations of proliferating elements are present in the vomeronasal sensory epithelium that are placed, respectively, in the supporting cell layer, at the boundaries between the sensory epithelium (S-VNO) and the non-sensory (NS-VNO) and in the basal region of the S-VNO. The number of dividing cells at the boundaries of the S-VNO is by far prevailing. Few proliferating cells located adjacent to the basal membrane are, however, present 1 day after BrdU inoculations. Seven days after BrdU treatment immunopositive nuclei were detected in more central regions of the VNO and at longer survival times they were also positive to carnosine, a marker of fully differentiated neurons. In conclusion, the present results suggest that at least two populations of VNO neuronal precursors are responsible for cell replacement throughout life.