Tight glycemic control by insulin, started in the preischemic, but not postischemic, period, protects against ischemic spinal cord injury in rabbits.

BACKGROUND

It is not well established whether insulin protects against ischemic spinal cord injury. We examined the effects of a single dose of insulin that corrects mild hyperglycemia on the outcome after transient spinal cord ischemia in rabbits.

METHODS

We assigned rabbits to four groups (n = 8 in each); untreated control (C) group, preischemic insulin (Pre-I) group, preischemic insulin with glucose (GI) group (glucose concentrations were maintained at levels similar to the C group by the administration of glucose), and postischemic insulin (Post-I) group. Insulin (0.5 IU/kg) was administered 30 min before ischemia in the Pre-I and GI groups, and just after reperfusion in the Post-I group. Spinal cord ischemia was produced by occluding the abdominal aorta for 13 min. Neurologic and histopathologic evaluations were performed 7 days after ischemia.

RESULTS

The mean blood glucose concentration before ischemia in the Pre-I group (118 mg/dL) was significantly lower than in the other three groups (158-180 mg/dL) and those of 30 min after reperfusion in the Pre-I (92 mg/dL) and Post-I (100 mg/dL) groups were significantly lower than in the C (148 mg/dL) and GI (140 mg/dL) groups. The motor function score and number of normal neurons in the anterior lumbar spinal cord in the Pre-I group were significantly greater than in the other three groups.

CONCLUSIONS

These results suggest that a relatively small dose of preischemic insulin protects against ischemic spinal cord injury, and that the protective effects result from tight glycemic control before ischemia.