DIABETES IMPAIRS SCIATIC-NERVE HYPEREMIA INDUCED BY SURGICAL TRAUMA -IMPLICATIONS FOR DIABETIC NEUROPATHY

The most widely used methods to assess nerve blood flow in diabetic ra ts are hydrogen clearance polarography and laser Doppler flowmetry, te chniques requiring surgical exposure of the nerve. In these experiment s, we examined the hypothesis that the trauma of surgical exposure int roduces an important and hitherto largely unrecognized variable that c ould account for discordant reports on nerve blood flow changes induce d by diabetes. We used the noninvasive (for sciatic nerve reference sa mple microsphere method to quantify sciatic nerve blood flow in unexpo sed vs. surgically exposed nerves in rats with streptozotocin-induced diabetes (at different temperatures and after curarization) and in une xposed vs. surgically exposed net-yes in galactose-fed rats. Baseline resting blood flow in unexposed nerves in both animal models of diabet es was either normal or increased !but was decreased in diabetic rats given d-tubocurarine). Furthermore, the normal brisk hyperemic nerve b lood flow response to the minimal trauma associated with surgical expo sure of the nerve was markedly impaired in diabetic and in galactose-f ed rats. Normalization of the blood flow response to trauma in galacto se-fed rats by an aldose reductase inhibitor suggests that the impairm ent is linked to increased polyol pathway metabolism. These findings 1 ) confirm our previous findings that sciatic nerve blood flow in diabe tic rats is increased or unchanged in unexposed nerves, while also con firming reports that in surgically exposed nerves blood flow is higher in control than in diabetic rats, and, 2) indicate that blood flows i n surgically exposed nerves are largely a measure of vascular response s to injury rather than (patho)physiological blood flow in undisturbed nerves.