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

脑缺血后能量代谢和功能的可逆性和可塑性与神经元成熟程度有关。然而，定量评估从脑损伤中恢复的能力是困难的，因为未成熟动物和成年动物之间代谢紊乱的程度明显不同。采用全脑缺血模型，在给予相同程度的缺血损伤的情况下，比较幼犬、幼犬和成年犬的恢复时间。方法将12只成年犬分为A组，成年犬4只(1岁)，青年犬4只(3月龄)，C组4只幼犬(38天)。动物在Innovar麻醉下切开气管，吸入30%氧气，用Pho-Energetics 250-80型核磁共振波谱仪获得磁共振波谱。同时记录顶叶皮质脑电。闭塞无名动脉和左锁骨下动脉…造成全脑缺血更多。结果*核磁共振波谱：全脑缺血时，A组缺血值与对照组的β-ATP比值降至0.31±0.03，B组降至0.38±0.03，C组降至0.43±0.05。再循环4小时后，B组和C组的-ATP比值分别恢复到0.90+-0.01和0.97+-0.04，而A组恢复到0.71+-0.05。B组和C组的ATP恢复水平明显高于A组(P&lt；0.00)，而PCR/PI的恢复时间进程在三个年龄组之间没有差异。(图2)*EEG；A组：缺血开始后，α波(813 Hz)几乎全部消失，未见明显恢复。(图3)B组：脑电恢复不完全，恢复延迟。C组：脑电恢复至接近对照组水平，但与3lp核磁共振波谱变化相比，恢复明显延迟。(图4)讨论这项31P核磁共振研究监测了全脑缺血期间的ATP耗竭，并评估了不同年龄狗的恢复阈值水平。持续15分钟的ATP水平从正常水平下降到30%-40%会导致幼年狗几乎完全恢复，而成年动物则表现出不可逆转的脑损伤。在婴儿的情况下，脑电几乎完全恢复。脑电恢复仅有时间延迟。较少

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