“… free glycine …, vinblastine , colchicine, Nocodazole, and 2,4-dinitrophenol (2,4-DNP).6.Comparative studies of other amino acids [3H-leucine,3H-serine,3H-glutamic acid,… demonstrates, for the first time, that a free amino acid, glycine, is transported in the retrograde direction within a select group of axons.”