IMPAIRED INDUCTION OF VASOACTIVE INTESTINAL POLYPEPTIDE AFTER SCIATIC-NERVE INJURY IN THE STREPTOZOTOCIN-DIABETIC RAT

This study was designed to assess the effects of experimental diabetes and nerve crush injury upon vasoactive intestinal polypeptide (VIP) c ontent and axonal transport in the dorsal root ganglia (DRG) and sciat ic nerve. Sciatic nerve crush injury in control and 3-week streptozoto cin-diabetic rats was followed 6.5 days later by placement of 2 constr icting ligatures above the site of injury. After 12 h, the L4 and L5 D RG and sciatic nerve were removed for VIP radioimmunoassay. Similar sa mples were also taken from control and diabetic rats whose nerve had b een ligated without a preceding crush. VIP was increased over 2-fold i n ganglia and 4-fold in nerves of crush-injured controls compared to u ninjured controls (both P < 0.01). Crush injury also increased ganglio n and nerve VIP in diabetic rats (P < 0.05 and 0.01, respectively) but the increase was less than what occurred in crush-injured controls (b oth P < 0.05). The accumulation of VIP proximal to a sciatic ligature was similar in control and diabetic rats and was not altered in either group by crush injury, while retrograde transport of VIP was initiate d by crush injury in both control and diabetic rats. These data show t hat short-term diabetes does not alter the amount and peripheral axona l transport of VIP in the sciatic nerve but impairs the ability of per ipheral nerve to respond to injury.