Variations in the cellular incorporation of [3H]proline

Injections of [3H]proline into various CNS nuclei in the cat and into the rat dorsal column nuclei labeled terminal targets of those regions despite the fact that only glia (and not neuronal somata) were labeled at the injection site. In contrast, although injections into cat CNS fiber tracts labeled glial cells surrounding the axons, neither the axoplasm, somata or terminals of those axons were labeled. In addition, injections into cat PNS dorsal root ganglia labeled ganglion cells. These results support previous findings suggesting that 3H-proline is incorporated into a class of molecules in the CNS (but not PNS) that is transferred from glia into neuronal somata (but not axoplasm).