Anterograde and retrograde axonal transport of native and derivatized wheat germ agglutinin in the visual system of the chicken

The anterograde and retrograde rates of axonal transport of the lectin wheat germ agglutinin (WGA) were investigated using native and derivatized lectins in embryonic (stage 39) and posthatch chickens. Anterograde transport rates in the retinotectal projection of posthatch animals ranged from 168 mm/day for native WGA to 345 mm/day for horseradish peroxidase conjugated WGA. Anterograde transport rates in embryos were at least 258 mm/day based on experiments employing tritium and horseradish peroxidase conjugates. Retrograde rates measured by appearance of label in the isthmo-optic nucleus in both embryonic and posthatch chickens were in the range of 150-180 mm/day. A fluorescein isothiocyanate conjugate of WGA was transported retrogradely but not anterogradely. When the extraocular eye muscles were labeled accidentally during injection, cells in the oculomotor or trochlear nuclei were more intensely labeled than neurons in the isthmo-optic nucleus. It was concluded that at least some conjugates of WGA, and possible the native lectin as well, travel in the fastest component of axonal transport. In view of the known intercellular movement of WGA from labeled presynaptic processes, it is recommended that survival times be kept short in experiments using WGA as a neuronal tracing agent (less than 24 h) to minimize the possibility of uptake and redistribution of the lectin by nearby cells.