Axonal transport of taurine along neonatal and young adult rat optic axons

Studies in this laboratory have indicated that taurine is axonally transported along goldfish optic nerves. In the present experiments the axonal transport of taurine was examined in neonatal and young adult rat optic axons. [35S]taurine was injected into the vitreous humor of right eyes of developing (1--15-day-old) or young adult (40-day-old) rats. At various times after injection ranging from 3 h to 7 days, right retinae and left and right geniculates were removed and assayed for radioactivity, left minus right lateral geniculate (L-RLG) radioactivity being used as an index of axonally transported [35S]taurine. Results indicated that taurine was rapidly transported along both neonatal and young optic axons, in contrast to other amino acids (i.e., leucine and proline) which are not axonally transported in this system. Significant developmental variations were seen in both L-RLG and right retinal [35S]taurine activity 24 h after injection. The amounts of L-RLG [35S]taurine corrected for retinal ganglion cell uptake in animals injected at 1,4,7 and 11 days after birth (prior to and during the major period of synaptogenesis in the geniculates) were 4.5, 3.1, 2.3 and 2.6 times higher, respectively, than those in the young adults. In contrast, the amount of corrected L-RLG [35S]taurine in animals injected at 15 days after birth (after synaptogenesis) were not significantly different from that in the young adult.