^<31>P NMR and EEG study of transient global ischemia in developing dog brain compared with adult dog

点击翻译按钮获取中文摘要

The reversibility and plasticity of brain energy metabolism and function after ischemic insult is related to the degree of neuronal maturation. A quantitative estimation of the capability to recover from brain damage, however, is difficult, because the degree of metabolic derangement differs markedly between immature and adult animals. Using a global ischemia model, and giving the same degree of ischemic insult, we compared the recovery time course among infant, young and adult dog groups.MethodsTwelve mongrel dogs from three age groups were used for the study Group A, 4 adult(one year) ; Group B, 4 young adult dogs(three months) ; Group C, 4 infant dogs(38 days). Animals were tracheotomized under Innovar anesthesia, and ventilated with 30% oxygen.Magnetic resonance spectra were obtained using a Phospho-Energetics 250-80 NMR spectrometer. Simultaneously, the parietal cortical EEG was recorded. Global ischemia was produced by occlusion of both the innominate and left subclavian arteries … More . Hypotension(Systolic blood pressure less than 100 mm Hg)was produced by withdrawal of blood.Results*NMR spectra ; During global ischemia, the beta-ATP ratio, ischemia value to control value, decreased to 0.31<plus-minus>0.03 in Group A, 0.38<plus-minus>0.03 in Group B and 0.43<plus-minus>0.05 in Group C. There were no significant differences among the three age groups. Four hours after recirculation, the -ATP ratio of Groups B and C returned to 0.90<plus-minus>0.01 and 0.97<plus-minus>0.04 respectively, while in Group A the ratio returned to 0.71<plus-minus>0.05. The level of ATP recovery in Group B and C significantly larger when compared to Group A(P<0.00On the other hand, the recovery time course of PCr/Pi showed no differences among the three age groups. (Fig. 2)*EEG ; Group A : With the onset of ischemia, almost all(alpha waves(813Hz)disappeared and there was no apparent recovery. (Fig. 3) Group B : The recovery of EEG was incomplete and recovery was delayed when compared to3 : LP spectral changes. Group C : The EEG recovered to near the control level, however, recovery was delayed remarkably when compared with3lp NMR soectral changes. (Fig. 4)DiscussionThis 31P NMR study monitored ATP depletion during global ischemia and evaluated the threshold level for recovery in dogs of various ages. An ATP reduction to 30-40% from the normal level sustained for 15 minutes results in nearly full recovery in infant dogs, while adult animals showed irreversible brain damage. In the case of infant, the EEG recovered almost completely. Only time delay of EEG recovery was seen. Less