The detection of motor nerve injury by MUNE in an animal model of diabetes / 天津医药

ABSTRACT

Objective To investigate motor nerve function status in rats with diabetes mellitus by motor unit number estimation (MUNE), and discuss it′s early diagnostic value in diabetic peripheral neuropathy (DPN). Methods Diabetic rat model (DM group) was induced by streptozotocin. The MUNE of gastrocnemius muscle and motor nerve conduction (MCV, CMAP) of the sciatic nerve were measured at the 4th, 8th and 12th week after onset of hyperglycemia in the DM group and the control group (normal SD rats). The ultrastructure of sciatic nerve was observed by electron microscope. Results At the 4th week, MUNE of gastrocnemius muscle was significantly decreased in DM group compared to that of the control group (275.88 ± 87.87 vs 369.71 ± 75.64,P<0.05). There were no significant differences in MCV and CMAP of sciatic nerve be?tween two groups. The electron microscopy observation showed that most nerve fibers were normal;a small amount of axonal atrophy, and myelin lamellar structure was separated in DM group. At the 8th week, compared with the control group, MUNE were reduced in gastrocnemius muscle in DM group (357.49±72.68 vs 221.26±92.41, P<0.01). There were no significant dif?ferences in MCV and CMAP of the sciatic nerve between DM group and control group. The electron microscope observation showed that part of nerve fibers were normal, the myelin focal plate layer was loose and separated, axonal atrophy, the axonal membrane and myelin sheath inner layer was separated with big gap. At the 12th week, MUNE of gastrocnemius muscle (127.87±19.80 vs 366.85±51.25), sciatic nerve MCV [(35.06±4.43) m/s vs (50.47±6.07) m/s] and CMAP [(2.91±1.37) mV vs (5.98±2.14) mV] were significantly decreased in DM group than those of control group (P<0.01). The electron microscopy observation showed severely damaged myelin flex and axonal squeeze. Conclusion MUNE is much earlier in detecting ear?ly motor nerve dysfunction in DM than conventional motor nerve conduction test.