CILAZAPRIL AND DIETARY GAMMA-LINOLENIC ACID PREVENT THE DEFICIT IN SCIATIC-NERVE CONDUCTION-VELOCITY IN THE STREPTOZOTOCIN-DIABETIC RAT

Young adult male Hooded Wistar rats were rendered diabetic by administ ration of streptozotocin and maintained for 5 weeks on a diet containi ng either 6% olive oil as the total source of fat (OO diet), or purifi ed gamma-linolenic acid (GLA) at a concentration of 0.5% with the rema ining 5.5% provided by olive oil (GLA diet). Rats were treated with th e angiotensin converting inhibitor, cilazapril, administered in the dr inking water at a dose of 20 mg kg(-1) body weight day(-1) For the OO diet groups, sciatic nerve conduction velocity (NCV) in diabetic rats was reduced by 32% (p < 0.01) in comparison with nondiabetic (vehicle- treated) rats and 27.5% (p < 0.05) in comparison with diabetic rats tr eated with cilazapril. Diabetic, cilazapril-treated rats showed no red uction in NCV. For the nondiabetic, diabetic, and diabetic plus cilaza pril groups fed GLA, the NCV was not significantly different, indicati ng that dietary GLA also prevented the deficit in the NCV induced by t he diabetic state. Analysis of the sciatic nerve endoneurial phospholi pid fatty acids revealed a significant reduction in the proportion of GLA and an elevation in the proportion of linoleic acid in the diabeti c groups compared with the nondiabetic groups and this was independent of the cilazapril treatment or the dietary lipid supplement. Sciatic nerve myo-inositol content was unaltered while mannose, fructose, gluc ose, and sorbitol levels were elevated in the diabetic groups and thes e changes were independent of the cilazapril treatment or the dietary lipid supplement. These results indicate that in the rat, cilazapril t reatment or dietary GLA, at the doses tested, are effective in prevent ing the deficit in the NCV induced by diabetes. (C) 1998 Elsevier Scie nce Inc.