The ultrastructure of cutaneous type I mechanoreceptors (Haarscheiben) in cats following denervation.

Denervation of specialized cutaneous mechanoreceptors (Haarscheiben or domes) in cats was followed after 20 and 25 days by the following alterations in receptor structure: (1) reduced numbers of Merkel cells, (2) Merkel cells degenerating in situ, (3) fewer dense-core granules in the cytoplasm of Merkel cells, (4) an increased number of agranular dendritic cells and Langerhans cells in the dome, (5) the apparent phagocytosis of Merkel cells by Schwann and Langerhans cells, (6) fewer epithelial cell layers over the dome, and (7) a decrease in the number of transitional cells. Skin excised between the domes in the denervated nerve field appeared normal when compared to innervated skin, and it was considered unlikely that the alterations in dome structure were due to generalized nutritional changes in the skin caused by transection of sympathetic axons or to some other side effect of denervation. Since domes are formed in new locations on the skin after nerves have regenerated (Burgess et al., '74), changes in dome structure following nerve transection are probably due to loss of the "trophic" influence of the nerves supplying the dome.