Effects of a Protein Synthesis Inhibitor on Hippocampal Neuronal Damage of Rats in the Ventricular Fibrillation Cardiac Arrest Model

ABSTRACT

BACKGROUND: The goal of successful resuscitation is not only to stop the process of ischemia as soon as possible but also to overcome the secondary injury process after resuscitation, which involves a complex interplay of mechanisms. Brain damage accompanying cardiac arrest and resuscitation is frequent and devastating. Cells die by one of two mechanisms necrosis or delayed neuronal death. Delayed neuronal death may require protein synthesis. Neurons in the CA1 subfield of the hippocampus are selectively vulnerable to death after injury by ischemia and reperfusion. Death of these neurons occurs after an interval of 1 or 2 days. We assessed the effects of a protein synthesis inhibitor, cycloheximide(CHX), on hippocampal neuronal death of rats by using the ventricular fibrillation cardiac arrest(VFCA) model. METHODS: The effect of CHX(3mg/kg, s.c.) on hippocampal neuronal death was studied in two groups of 18 rats each, one group being subjected to a 2-min VFCA and the other to a 3-min VFCA. Each group was divided into three subgroups control(group I,II) without subcutaneous injection of CHX, 'exp-12' of group I/II treated with CHX 12 hours after return of spontaneous circulation (ROSC), and 'exp-24' of group I/II treated with CHX 24 hours after ROSC. The coronal sections of the hippocampus levels were stained with hematoxylin-eosin after 72 hours of survival. The histologic damage score(HDS) was used to assign a score to the total number of damaged neurons counted in each of the hippocampal CA1 subfields. RESULTS: 1. There were not significan differences in heart rates, blood pressures, blood sugar, and blood gas in group I & II during the pre-arrest steady state or at 5 min and 30 min after ROSC. 2. In group I & II, the HDS, were significantly reduced in rats(I exp-12, 1.1+/-0.6; I exp-24, 1.3+/-0.5; II exp-12, 1.4+/-0.7; and II exp-24, 1.8+/-0.8) treated with CHX 12 hours or 24 hours after ROSC than control rats(I, 2.5+/-0.9, II, 2.9+/-0.8)(p<0.05). CONCLUSION: These results suggest that delayed hippocampal neuronal death from ischemic insult after ventricular fibrillation cardiac arrest followed by resuscitation can be prevented by a protein synthesis inhibitor, CHX. Further experimental studies of the action mechanism of protein synthesis inhibitors to delayed neuronal death and clinical applications are required.