Axonal transport in the garfish optic nerve: comparison with the olfactory system

Abstract

Fast and slow axonal transports were studied in the optic nerve of the garfish and compared with previous studies on the olfactory nerve. The composition of fast-transport proteins was very similar in the two nerves. Although the velocity of fast transport was slightly lower in the optic nerve, there was a linear increase in velocity with temperature in both nerves. As in the olfactory nerve, only a single wave of slow-transport protein radioactivity moves along the nerve. The velocity of slow transport also increased linearly with temperature, but the coefficient was less than in the olfactory system. The composition of slow transport in the optic nerve was significantly different from that in the olfactory nerve, a finding reflecting the different cytoskeletal constituents of the two types of axons. The slow wave could be differentiated into several subcomponents, with the order of velocities being a 105-kilodalton protein and actin greater than tubulins and clathrin greater than fodrin much greater than neurofilaments. It can be concluded that the temperature dependence of fast and slow axonal transport in different nerves reflects the influence of temperature on the individual polypeptides constituting the various transport phases. The garfish optic nerve preparation may be advantageous for studies of axonal transport in retinal ganglion cell axons, because its great length avoids the complications of having to study transport in the optic tract or in material accumulating at the tectum.