Changes Of Auditory Evoked Potentials And Serum NSE In Rat Pups With Hypoxic-ischemic Encephalopathy

Objective:The dynamic changes of brainstem auditory evoked potentials(BAEP) and middle latency responses(MLR) from day 14 to 90 as well as the abnormal changes of serum neuron-specific enolase(NSE) had been observed in the rat pups with hypoxic-ischemic encephalopathy(HIE) to provide the new experimental evidence for their clinical application in early monitoring and objectively evaluating the brain and auditory injury as well as forecasting the prognostic in the neonates suffering from hypoxic-ischemic encephalopathy.Methods:The left carotid arteries of thirteen days-old Sprague-Dawley rat pups were ligated and cut off after the anesthetization with ether,and then they were placed within the box containing a gas mixture of 8%oxygen and 92%nitrogen for 2 and 3 hours in group HI2 and HI3 respectively.The left carotid arteries of the rat pups in control group were only isolated without other stimulations.BAEP and MLR of the rat were recorded with an evoked potential recorder at day 14,17,20,27,37,47,57,67,77 and 90.The enzyme-linked immunosorbent assay was used to detect the serum levels of NSE at 12,24 and 48 hours after the hypoxic-ischemic injury in the rat.Results:1.One hour reoxygenation after hypoxic-ischemic injury,the rat pups in group HI2 and HI3 rotated toward left side and crawled with the dragged right leg.2.All the PL and IPL ofⅠ-Ⅲ,Ⅲ-ⅤandⅠ-Ⅴof BAEP in the rat in group HI2 and HI3 from day 14 to 90 were significantly longer than that in control group(P＜0.05 or P＜0.01).The PL at all age stages of the rat were significantly longer in group HI3 than in group HI2(P＜0.05 or P＜0.01),and the IPL ofⅠ-Ⅲ,Ⅲ-ⅤandⅠ-Ⅴat day 47,67,77 and 90 were significantly longer in group HI3 than in group HI2(P＜0.05).All the PL and IPL ofⅠ- Ⅲ,Ⅲ-ⅤandⅠ-Ⅴshortened step by step with age,but they did not develop to the mature values at day 90.3.All the PL of MLR in the rat in group HI2 and HI3 from day 17 to 90 were significantly longer than that in control group(P＜0.05 or P＜0.01).The PL at all age stages of the rat were significantly longer in group HI3 than in group HI2(P＜0.05 or P＜0.01).The PL shortened with age,but they did not develop to the mature values at day 90.The IPL of Po-Pa,Pa-Pb and Po-Pb of MLR in the rat in group HI2 and HI3 from day 17 to 90 were significantly longer than that in control group(P＜0.05 or P＜0.01),and they were significantly longer in group HI3 than in group HI2(P＜0.05),except for the IPL of Pa-Pb from day 27 to 67 and at day 90 in group HI2 and from day 27 to 57 in group HI3.They also shortened with age,but they did not develop to the mature values at day 90 except for the IPL of Pa-Pb in group HI2.4.The serum levels of NSE at 12,24 and 48 hours after the hypoxic-ischemic injury in the rat in group HI2 and HI3 were significantly higher than that in control group(P＜0.05 or P＜0.01),and the serum levels of NSE at all stages of the rat were significantly higher in group HI3 than in group HI2(P＜0.05).Conclusions:1.There were constant abnormal changes of the PL and IPL in the rat pups with hypoxic-ischemic encephalopathy not only in BAEP,but also in MLR.The PL and IPL of them can be taken as the sensitive and objective parameters to early monitor the brain and auditory injury resulted from the hypoxic-ischemic stress in the neonatal period.A combination examination of BAEP and MLR is favorable for early diagnosing the abnormalities.2.The development of the PL and IPL of BAEP and MLR was significantly retarded,which was closely related to the degree of brain and auditory injury.They can be taken as the important parameters for monitoring,evaluating and prognosing the brain and auditory injury resulted from the hypoxic-ischemic stress in the neonatal period.3.The serum NSE is the sensitive and objective parameter for monitoring,evaluating and prognosing the brain injury resulted from the hypoxic-ischemic stress in neonatal period. A combination examination of the serum NSE and BAEP has important significance.