Moderate hypoglycemia impairs the function of the inferior colliculus in the awake rat

To assess the effect of acute hypoglycemia on the brain stem auditory pathway, we implanted electrodes into the inferior colliculus (IC) and subsequently recorded auditory-evoked potentials from the IC (ICEP) and brain stem (BAEP) in normal awake rats during euglycemic and hypoglycemic hyperinsulinemia (2 hours). Latencies of the ICEP and peak V of the BAEP were significantly prolonged by hypoglycemia (approximately 2.7 mmol/L). The change in the BAEP was principally between peak III and peak V. suggesting an effect in or near the IC. ICEP and BAEP latencies did not change during euglycemic hyperinsulinemia. We conclude that the function of the IC is very sensitive to episodes of moderate hypoglycemia. These data provide direct evidence that the scope of adverse central nervous system effects resulting from hypoglycemia extends beyond cognitive centers to include the brain stem.