Surface changes in the rat vomeronasal epithelium during degeneration and regeneration of sensory receptor cells

To investigate cell turnover in the vomeronasal epithelium we used electron microscopy to obtain quantitative measurements of changes observed at the surface of the sensory epithelium. Receptor cell degeneration was induced b y sensory nerve transection and animals were examined at postoperative reco very times of 4, 6, 10, 15, 35 and 60 days. We measured the number and dens ity of receptor and supporting cells, and membrane length at the surface of the sensory epithelium. The number of receptor cells rapidly decreased dur ing the degeneration period, reaching a minimum at 6 days. After 15 days of recovery the number and density of receptor cells returned to control leve ls. The surface membrane length for regenerated receptor cells was similar to that of controls, however the morphological appearance was characteristi c of immature cells. In contrast to the receptor cells, the number and dens ity of supporting cells did not change during degeneration and regeneration . However, there was a significant increase in the length of supporting cel l-surface membranes. These results suggest that during receptor cell degene ration, supporting cell membranes compensate for the loss of receptor cells by expanding their surface membrane length to help to maintain the continu ity of the epithelial surface. Thus, an important role of vomeronasal suppo rting cells may be to maintain the structural integrity of the epithelium d uring turnover of the receptor cell population.