Effects of the application of erythropoietin on cerebral recovery after cardiac arrest in rats

Abstract

Background: After transient global cerebral ischaemia, selectively vulnerable areas of the brain show delayed neuronal degeneration. Recent data have demonstrated potent neuroprotective effects of the application of growth hormones like erythropoietin (EPO) after focal cerebral ischaemia. In order to assess possible effects of the application of EPO on cerebral recovery after cardiac arrest in rats, the vulnerable hippocampal CA-1 sector was investigated.

Methods: Thirty male Wistar rats were randomised into two groups (EPO versus placebo; n=15 per group). Cardiac arrest was induced by ventricular fibrillation during general anaesthesia. After 6 min of global cerebral ischaemia, animals were resuscitated by external chest compressions combined with defibrillation. Investigator blinded bolus application of EPO (5000 IE/kg bodyweight) and placebo was performed at three different time points, respectively: 5 min before cardiac arrest (i.v.; intravenously), 24h (i.p.; intraperitoneally) and 72 h (i.p.) after ischaemia. At 24h, 72 h and 7 days, animals were tested according to a neurological deficit score. After of reperfusion, coronal brain sections were analysed by TUNEL- and Nissl-staining. A caspase activity assay was done to determine antiapoptotic properties of EPO. Statistical analyses were done using ANOVA.

Results: Neurological deficit scoring did not show differences between the groups. However, in all groups typical delayed neuronal degeneration could be found in the CA-1 sector. There was no difference in neuronal survival between the groups (viable neurons EPO (median [interquartile range]): 15.5 [10.1-21.3]; placebo: 16.8 [7.7-26.3]). Results from TUNEL-staining revealed no differences in the amount of apoptotic cell death between the groups (EPO: 71.2 [58.1-81.8]; placebo: 73.4 [67.8-78.2]). Caspase activity assays demonstrated a strong expression of general caspase activity as well as caspase-3 activity in the CA-1 sector and the nucleus reticularis thalami, without any differences between both groups.

Conclusion: Despite the well known neuroprotective properties of EPO in ischaemia induced neuronal degeneration, this study could not reveal any beneficial effects of EPO after global cerebral ischaemia due to cardiac arrest in rats.