Axonal transport of glycerophospholipids in regenerating sciatic nerve of the rat during aging.

The effect of age upon the axoplasmic transport of glycerophospholipids has been studied using as a model the regenerating sciatic nerve of young (2-month-old), young adult (6-month-old), middle-aged (16-month-old), and aged (20-month-old) male rats. The right sciatic nerve was crushed 0.5 mm down the incisura ischiadica. Four and nine days after the lesion, a mixture of [2-3H] glycerol and [methyl-14C] choline was bilaterally injected into the spinal cord, at a level of the L4-L5 vertebrae. The animals were killed 18 hr after the isotope injection. Proximal and distal portions of crushed nerve and of contralateral sham-operated ones were dissected and consecutive 5-mm segments were subjected to lipid extraction and analysis. The findings of the present study are summarized as follows: (1) The accumulation of labeled lipid material axonally transported four days after nerve injury was mainly located at the crush site in young, young adult, middle-aged, and aged rats. The accumulation of both 3H-glycerolipids and 14C-choline phospholipids in postcrush segments was markedly higher for young and young adult than for aged rats, four and nine days after crush; (2) the average rate of axonal regeneration, determined between days 4 and 9 following crush injury was 3.6 and 4.2 mm/day for 2-month-old and 6-month-old rats, respectively; it decreased to the value of 2.5 mm/day for 16-20-month-old rats.