Effects of insulin and hypoglycemia on the auditory brain stem response in humans.

1. This study aimed to differentiate effects of insulin and hypoglycemia on sensory brain stem functions in humans. Auditory brain stem responses (ABR) were examined in 30 healthy men during euglycemia and after 20 and 50 min of steady-state hypoglycemia of 2.6 mM induced with human insulin (HI) in one session and porcine insulin (PI) in another session. 2. Levels of blood glucose and serum insulin were identical in both sessions during HI and PI infusion. 3. Hypoglycemia increased interpeak latencies III-V (+71 microseconds; P < 0.001) and I-V (+123 microseconds; P < 0.001), whereas changes in the latency of wave I were not significant. 4. After 20 min of constant hypoglycemia, increases in the interpeak latencies I-V and III-V were significantly more pronounced during infusion of PI than HI. These differences disappeared with time spent in hypoglycemia, i.e., after 50 min of hypoglycemia. 5. Apart from the delaying effect of hypoglycemia on neuronal transmission within the sensory brain stem, the results provide evidence for a separate influence of insulin on these functions.