Rate of axoplasmic transport of substances in spinal ventral roots of old rats and its dependence on energy metabolism

An aqueous solution of ¹⁴C]-L-leucine (specific activity 339 mCi/mmole) was injected in a dose of 7–8 µl into the region of the ventral horn of mature (8–12 months) and old (26–28 months) rats at the level of segments L5–L6 of the spinal cord. Radioactivity of different segments of the corresponding ventral roots was tested after 1–2.5 h. Labeled substances (including protein) were shown to migrate in mature rats in a rapid flow with a velocity of 408±10.9 and 380±22 mm/24 h, respectively, whereas in old rats the velocity was 217±11.3 and 200±40 mm/24 h. Slowing of the axoplasmic current in old rats increases with increasing distance from the neuron body. Uncoupling of oxidation and phosphorylation by injection of 2,4-dinitrophenol, inhibition of glycolysis by sodium fluoride, and hypoxic hypoxia all induce more marked slowing of the axoplasm flow in old rats. Small doses of sodium fluoride, on the other hand, accelerate the flow of axoplasm, and this correlates with elevation of the cAMP level in the ventral roots.Institute of Gerontology, Academy of Medical Sciences of the USSR, Kiev. Translated from Neirofiziologiya, Vol. 16, No. 2, pp. 189–194, March–April, 1984.