Nocodazole irreversibly reduces the capacity of rapid axoplasmic transport in vitro

Using the frog sciatic nerve as an in vitro model system, the effects of 10(-5) M nocodazole, an antimitotic drug, on rapid axoplasmic transport were quantified and tested for reversibility. After pulse-labeling the 8th dorsal root ganglia with [3H]leucine, the nerves were incubated for 4.5 to 9 hr at 25 degrees C. Transport velocities and amounts of transported material were determined from the distribution of radioactively labeled proteins. One nerve per animal served as a control. Before ganglia labeling, the nerves were preincubated for 1 or 15 hr in 10(-5) M nocodazole, respectively. In one set of experiments, the nerves were preincubated in nocodazole for 6 hr washed for 1.5 hr and further treated in Ringer's solution to test for reversibility. We found that nocodazole did not affect the maximal transport velocity under any of the conditions tested. The amounts of rapidly transported material were reduced to 60% of controls after 1 hr of pretreatment with nocodazole, and to 30% after 6 to 15 hr of pretreatment. There was no indication for a reversibility of these effects. We conclude that 10(-5) M nocodazole shows maximal effects on rapid axoplasmic transport only if given several hours before protein synthesis, and that it reduces the capacity of rapid axoplasmic transport without affecting transport velocity. These effects are not reversible during the survival time of the in vitro preparation.