Taurine depletion leads to loss of rat optic nerve axons

The number of axons in the optic nerve have been examined in rat pups raised by control or taurine-depleted mothers, at 21, 28 and 40 days after birth. Optic nerves from the mother rats were also studied. Taurine depletion of dams and some litters after weaning was achieved by in vivo treatment with guanidinoethyl sulfonate, an inhibitor of taurine transport. Retinal taurine content was reduced by this procedure and reductions in axon density (axons per area) were found in some groups. Comparison of axon densities obtained from light or electron micrographs suggested that taurine-deficient pups might have a higher proportion of small diameter fibres than controls, perhaps due to slowed growth and/or myelination. Reductions in the calculated total number of optic nerve fibres attained statistical significance consistently only in the treated dams. Ganglion cell degeneration may be direct or secondary to effects on taurine-sensitive elements at more distal retinal sites.