Rapid axoplasmic transport in the olfactory nerve of the pike: I. Basic transport parameters for proteins and amino acids

Abstract

The rapid axoplasmic transport parameters have been established for proteins and amino acids in the olfactory nerve of the pike, Esox lucius. this olfactory system has been found well suited for investigating the dynamics of axoplasmic transport and offers distinct advantages for biochemical analyses. An evaluation of isotope distribution profiles has established the following. (1) Maximum transport velocities for proteins are 151 ± 5 mm/day at 19 °C and 106 ± 6 mm/day at 15 °C. (2) Apparent somal delay times for proteins are 1.9 h at 19 °C and 2.3 h at 15 °C. (3) The free amino acid V max is identical to the protein V max. (4) Free amino acids have no somal delay time and exit from the soma immediately after isotope application. (5) Rapidly transported proteins display a fast turnover at the nerve terminals. (6) Intact nerves reveal only wavefronts of radioactivity whereas removal of the cell bodies 4 h after isotope application produces characteristic peak and saddle regions that demonstrate a loss of material by the peak during transport. (7) The average velocity of material in the peak region is 127 mm/day at 19 °C. Most parameters are identical to those of the six times longer garfish olfactory nerve. Axoplasmic transport in C-fibers is therefore independent of fiber length. The temperature dependence of the pike V max also agrees with the garfish temperature function which can be linearly extrapolated to the mammalian transport V max. The pike olfactory system presents, therefore, further evidence that a common, temperature-correlatable V max may exist in all nerves.