Carbohydrates play a role in neurite outgrowth in vivo during development and regeneration

We have used the alpha-glucosidase inhibitor, castanospermine, to investigate the possible involvement of N-linked glycosylation in the process of neurite outgrowth both during the development and regeneration of sympathetic nerve fibres into the iris of the rat. The effects on nerve growth were assessed qualitatively using catecholamine histochemistry and quantitatively by measuring the uptake of [3H]noradrenaline. Castanospermine was injected during the first, second or third postnatal week or during the second to fourth week after degeneration of adrenergic nerve terminals with the neurotoxin, 6-hydroxydopamine. Results showed that both the initial growth of sympathetic nerve fibres, as well as the regeneration of these fibres, was inhibited by castanospermine treatment. The inhibitory effects were restricted to injection of castanospermine at particular time periods during postnatal development and regeneration. These results suggest that N-linked carbohydrates may be important in particular stages of the processes of initial nerve growth and regeneration of sympathetic nerve fibres in the iris.