Fluorescence microscopical study on fibre formation from carotid bodies from normal or dexamethasone-treated postnatal rats in intraocular transplants to adult rats.

Carotid bodies from untreated newborn and adult rats or dexamethasone-treated 7-day-old and adult rats were homologously transplanted into the anterior eye chamber of adult female rats. The eyes of the host rats were sympathetically denervated one day before the transplantation. The transplants and irides were examined at various times postoperatively by formaldehyde-induced catecholamine fluorescence. Transplants attached to and were vascularized by the iris of the host eye. The carotid body glomus cells in the transplants from untreated newborn and dexamethasone-treated 7-day-old rats regularly migrated on the iris, while migration from the adult carotid body transplants occurred only occasionally. The migrated glomus cells usually grew only short processes, but in one out of 55 transplants from untreated newborn rats and in one out of 48 transplants from untreated adult rats a fibre network was formed around the transplant. Twenty three transplantations from 7-day-old dexamethasone-treated rats were made and in 5 of them a fibre network was formed around the transplant. In some cases the nerve fibres could be seen to extend from individual glomus cells. There was no fibre outgrowth from the 13 carotid bodies transplanted from dexamethasone-treated adult rats. Pieces of adrenal medullary tissue, which previously has been shown to partially reinnervate the sympathetically denervated iris, was transplanted for comparison. They always formed a fibre network around the transplant. It is concluded that carotid body glomus cells do not have the phenotypic plasticity to form nerve fibres in intraocular transplants as do the adrenal medullary cells.(ABSTRACT TRUNCATED AT 250 WORDS)