Effect Of Ephedrine In Neural Function Of Neonatal Rats After Hypoxic-ischemic Brain Damage

OBJECTIVE:To investigate the effects of ephedrine on the expression of Nogo-A and synaptophysin in brain tissue of neonatal rats after HIBD.METHODS:Ninety-six 7-day-old Sprague-Dawley rat pups were randomly divided into 3 groups (n = 32 in each group): sham operation group, HIBD group and ephedrine intervention group. The HIBD model was prepared by permanent occlusion of left common carotid artery, followed by 120 min of hypoxia (8% oxygen and 92% nitrogen). In the sham operation group, the left common carotid artery was exposed but was not ligated or hypoxia. The ephedrine intervention group was intraperitoneally injected with ephedrine immediately after HIBD, at a dosage of 1.5 mg·kg-1, the sham operation group and HIBD group was injected with normal saline. All rat pups were treated once a day for seven days.Brain tissue was sampled at different time points (1, 2, 3, and 4 weeks) after HIBD. Hematoxylin-Eosin (HE) staining was used to determine histopathological damage. The expression of Nogo-A and synaptophysin protein were detected by immunohistochemical staining.RESULTS:1. Pathologic damage: The neuronal degeneration and edema was found in the ischemic cortex with HE staining.2. Nogo-A expression in the cerebral cortex: Compared with sham operation group, the expression levels of Nogo-A were significantly increased in the HIBD group at each time points (P<0.01). The Nogo-A expression in the ephedrine intervention group was significantly reduced than that in the HIBD group (P < 0.01).3. Synaptophysin expression in the hippocampus: The expression of synaptophysin in the hypoxic-ischemic cortex was significantly lower than that in the sham group (P < 0.01). Compared with the HIBD group, the synaptophysin levels of the ephedrine group were significantly increased (P < 0.01).CONCLUSIONS:The higher expression of Nogo-A protein may be a critical obstacle to nerve regeneration after HIBD. Changes in levels of Nogo-A was associated with opposite changes in synaptophysin. The application of ephedrine after HIBD normalized level of Nogo-A as well as synaptophysin. PART 2 EFFECT OF COMBINED THERAPY WITH EPHEDRINE AND HBO ON NEONATAL HYPOXIC-ISCHEMIC BRAIN INJURY OBJECTIVE: The aim of the present study was to evaluate the effect of a combination of ephedrine and hyperbaric oxygen (HBO) on neonatal hypoxic-ischemic brain injury. METHODS: 7-day-old Sprague-Dawley rat pups were randomly divided into sham operation, HI, ephedrine, HBO, and combined group. The ephedrine group was intraperitoneally injected with ephedrine, HBO group was treated for 2 hours at 2.5 absolute atmosphere (ATA) per day, the combined group received both ephedrine and HBO treatments, the sham operation and HI groups were intraperitoneally injected with normal saline. Rat brains at 7 days after HI, were collected to determine histopathological damage and the expression levels of Caspase-3 and Nogo-A. Four weeks after insult, animals were challenged with Morris water maze test.RESULTS:1. The growth rate of weight: The rate in each treatment group was higher than that of HI group 1week after HIBD (P < 0.05). Compared with the single treatment groups; the rate was significantly increased in the combined group (P < 0.05).2. Pathologic damage: The left hemisphere had evidence of cellular shrinkage and darkening extending throughout the ischemic cortex following HI. Similar changes were very few in the combined group and much reduced in the single treatment groups. In each single treatment group, however, relatively numerous damaged neurons were observed as compared to the combined group.3. Caspase-3 and Nogo-A protein expression: The expressions of Caspase-3 and Nogo-A were reduced in treating groups compared to those in HI group (P < 0.01). Compared with the single treatment groups, the expression levels of Caspase-3 and Nogo-A were significantly reduced in the combined group (P < 0.01).4. The Morris water maze test: Compared with the single treatment groups, the average time of escape latency was significantly shorter (P < 0.01) and the number of platform location crossing was more (P < 0.05) in combined group.CONCLUSIONS: These findings indicate that the combination of ephedrine and HBO can enhance the neuroprotective effect in the neonatal rat HI model partially mediated by inhibiting Caspase-3 and Nogo-A pathways.