Replacement of receptor cells in the hamster vomeronasal epithelium after nerve transection

Chemoreceptor cells in the vomeronasal and olfactory epithelium arereplaced following experimentally induced degeneration. This study analyzesquantitatively the time course and degree of vomeronasal receptor cellreplacement. Unilateral transection of the vomeronasal nerves in adulthamster was used to induce a retrograde degeneration of receptor cells inthe vomeronasal organ. Histological measurement of both number of receptorcells and epithelial thickness were made for recovery times from 0 to 60days. After nerve transection, there was a gradual degeneration of receptorcells, the number decreasing to 50% of control by day 2 and 16% by day 6.During days 7-15 maximum receptor cell replacement was observed. Cellnumber increased rapidly and reached a peak on day 15. At recovery times of40-60 days, cell number returned to the control level. Epithelialthickness, however, decreased to 60-70% during the degeneration period(days 4-6) and did not return to control levels. After 40-60 daysepithelial thickness remained at 70% of control. These results demonstratethat vomeronasal receptor cells are replaced following degeneration, butepithelial thickness does not return to control levels. These findingssuggest that the number of replacement cells is not limited by the reducedthickness of the epithelium, and that recovery mechanisms may function torestore an optimum number of receptor cells.