ACETYL-L-CARNITINE PREVENTS AGE-DEPENDENT STRUCTURAL ALTERATIONS IN RAT PERIPHERAL-NERVES AND PROMOTES REGENERATION FOLLOWING SCIATIC-NERVEINJURY IN YOUNG AND SENESCENT RATS

Morphologic and morphometric alterations of the sciatic nerve from old Sprague-Dawley rats and of lesioned tibial nerve from young and senes cent Sprague-Dawley rats were studied. The possible therapeutical effe cts of treatment with acetyl-L-carnitine (ALCAR) were also investigate d, ALCAR being a compound shown to exert a beneficial pharmacological action on diabetic neuropathies, Nerve sections from animals sacrifice d under anesthesia were stained with toluidine blue. In old rats, a 6- month treatment with ALCAR markedly reduced the percentage of myelinat ed fibers (MF) characterized by age-dependent morphologic alterations (4% in treated rats versus 11% in untreated ones), such as myelin ball oons, infolded loops of myelin, myelin reduplication, and ovoids. In t he lesioned animals, ALCAR-treatment (15-60 days for young rats and 6- 9 months for senescent rats) produced a significant increase versus co ntrols in the density of regenerating myelinated fibers (RMF) at 15 da ys (young rats) and at 30 days (senescent rats) after crush, as well a s an increase in the axon diameter in both young and senescent rats at 60 days after nerve crush. The MF diameter (sheath + axons) was signi ficantly larger in treated senescent rats than in controls at 100 days after nerve crush. In ALCAR-treated rats, both young and senescent, t he density of degenerative elements was lower and the RMF ratio (RMF d ensity/ RMF density + density of degenerative elements) was higher tha n that in controls at all detection times. (C) 1994 Academic Press, In c.