An electrophysiological analysis of brainstem function in rats with diabetes mellitus

Diabetes mellitus (DM) can affect both the peripheral and the central nervous system (CNS). However, central deficits are documented less well than peripheral deficits. We believe that brainstem auditory evoked potential (BAEP) studies help in the understanding of the dysfunction of the ascending sensory pathways at various levels. Twenty-two male rats were randomly divided into two groups: normal control rats (group NC) and diabetic rats (group DM). DM was induced by a single intraperitoneal injection of 1% streptozotocin (STZ, 60 mg/kg of body weight) in all rats of DM group. After six weeks, Absolute peak latencies (PLs) of waves I, II, III, IV and V, and interpeak latencies (IPL) of I-III, III-V and I-V were measured in each rats of the experiment. Then serum insulin levels, blood biochemical indices, superoxide dismutase (SOD) and malondialdehyde (MDA) were measured. The diabetic status of the rats of DM group was kept uncontrolled throughout the study. Body weight and blood glucose of non-fasting rats (BG) in DM group were significantly altered than those of NC group (P<0.05, respectively). Neuroelectrophysiological results showed that all wave latencies and IPL I-III, I-V in DM group were prolonged at 6 weeks after induction of diabetes, and delay in waves III, V and IPL I-III, I-V was significant compared with NC group (P<0.05, respectively). It was discovered that central conduction time (CCT) of rats with diabetes had a close correlation with fasting insulin (FINS), fasting blood glucose (FBG) and MDA. These findings indicate that experimentally induced diabetes can result in a brain dysfunction as measured by the increased latencies of the IPL I-V of BAEP. In conclusion, BAEP prove to be a useful non-invasive neuroelectrophysiological technique that may help unravel both the relative involvement of the peripheral and central nervous systems in the course of diabetes mellitus, and the evolution of diabetic neuropathy.