NEUROTROPHIC ACTIVITY OF BRAIN EXTRACTS IN FORELIMB REGENERATION OF URODELE, TRITURUS

The loss in protein synthesis which the regenerating forelimb of the newt suffers after denervation could be recovered by infusing into it an extract of newt soluble brain protein. The synthesis of basic protein showed a greater response to the active brain principle than did that of acidic protein. The active agent of the nervous tissue was destroyed by heat and trypsin digestion. Extracts of liver and spleen, similarly prepared, did not evoke recovery of lost protein synthesis. Synaptosomal extracts of the frog [Rana pipiens] brain also caused recovery of protein synthesis in the denervated regenerate, demonstrating the likelihood that the active agent was not species-specific within these amphibians, that it was a constituent of the neuronal fraction of nervous tissue and that it was present in axonal terminals. Additional experiments showed that the nervous agent was likely a basic protein, and that the amount of protein infused was of the order of only 1.0% of the total regenerate protein. The nature of the effect on protein synthesis and the nature of the active principle was discussed.