TRANSPORT OF CHOLESTEROL IN THE CHICK OPTIC SYSTEM

After injection of radioactive cholesterol into the vitreous humour of chicks, cholesterol is axonally transported along the optic nerve to the contralateral optic tectum. In the optic nerve of young chicks cholesterol is only transported at the slow rate whereas in the sciatic nerve of adult chicks it is transported at both the fast and slow rates. This difference is not due to age or a peculiarity of avian species as the same difference exists in mice. Estimates of the cholesterol content of tissues and the amount of cholesterol transported suggests the existence of small rapidly turning over pools of cholesterol in nerves. Due to its great metabolic stability, cholesterol is a useful and specific marker for slow transport in the optic nerve and thus may prove suitable for the mapping of neuronal projections.