FURTHER STUDIES OF TRANSPORT OF PROTEIN TO NERVE ENDINGS

Mice were injected intracerebrally with [l‐14C]leucine, and the specific activities of subcellular fractions of brain and effractions of isolated nerve endings were determined. There was a progressive increase in the specific activity of protein associated with isolated nerve endings after incorporation of [l‐14C]leucine into whole brain protein had terminated. Although, the incorporation of [14C]leucine into soluble protein of whole brain did not differ significantly in mice which were 3 months or 1‐year old, the subsequent increase in specific activity of soluble protein isolated from nerve endings was significantly greater in the younger animals; 6‐month‐old mice were intermediate. Therefore, changes in some aspect of the transport of protein to nerve endings is altered even after sexual maturity. Anaesthetization with pentobarbitone during incorporation of [14C]leucine into protein, and inhibition of protein synthesis with acetoxycycloheximide after incorporation of [14C]leucine was complete, did not interfere with the subsequent appearance of radioactive protein at the nerve ending. Evidence is presented for the transport, from a proximal site of synthesis, of protein associated with particulate components of the nerve ending, including synaptic vesicles. Copyright © 1968, Wiley Blackwell. All rights reserved