Tao Lian, Masri Daniel, Hrabetová Sabina, Nicholson Charles
Department of Physiology and Neuroscience, New York University School of Medicine, 550 First Avenue, New York, NY 10016, USA.
Brain Res. 2002 Oct 18;952(2):290-300. doi: 10.1016/s0006-8993(02)03254-7.
Spreading depression (SD) and ischemia are different pathophysiological events but have similar characteristics. This study investigated whether similarity exists in the light scattering (LS) properties during SD and ischemia in rat neocortical slices. SD was induced by injection of K(+) while ischemia was simulated by removing oxygen and glucose. LS was simultaneously recorded with changes in extracellular direct current (DC) potential and extracellular space (ECS) volume. LS was measured using a photon counting fiber optic system and the ECS volume change was determined by measuring the ECS concentration of tetramethylammonium (TMA(+)). Slices maintained in normal artificial cerebrospinal fluid (ACSF) showed a consistent LS increase during SD, but exhibited two different LS behaviors during 6 min of ischemia. In eight slices, LS decreased and remained so until the end of the ischemic challenge. In another 10 slices, LS diminished initially but, after 2 min, suddenly reversed sign, accompanied by a rapid negative shift in extracellular DC potential. When 50 or 91% of Cl(-) in the ACSF was replaced by membrane-permeable propionate, LS retained its increase during SD, but always showed the sudden LS reversal during ischemia. In contrast, when Cl(-) was substituted with membrane-impermeant methylsulfate, the SD-induced LS increase was replaced by an LS decrease, and the sudden LS reversal during ischemia was absent. While the LS signal showed different characteristics during SD and ischemia, the DC potential always presented negative shifts and the ECS volume always exhibited similar decreases. These results suggest that the polarity of the LS signal is determined by the competition of at least two factors: cell swelling and anion influx.
扩散性抑制（SD）和局部缺血是不同的病理生理事件，但具有相似的特征。本研究调查了大鼠新皮质切片在SD和局部缺血过程中光散射（LS）特性是否存在相似性。通过注射钾离子诱导SD，同时通过去除氧气和葡萄糖模拟局部缺血。在记录细胞外直流（DC）电位和细胞外间隙（ECS）体积变化的同时记录LS。使用光子计数光纤系统测量LS，并通过测量四甲基铵（TMA⁺）的ECS浓度确定ECS体积变化。维持在正常人工脑脊液（ACSF）中的切片在SD期间LS持续增加，但在6分钟的局部缺血期间表现出两种不同的LS行为。在8个切片中，LS降低并一直保持到缺血刺激结束。在另外10个切片中，LS最初降低，但在2分钟后突然反转，同时细胞外DC电位快速负向偏移。当ACSF中50%或91%的Cl⁻被可透过膜的丙酸盐替代时，LS在SD期间保持增加，但在局部缺血期间总是表现出突然的LS反转。相反，当Cl⁻被不可透过膜的甲硫酸盐替代时，SD诱导的LS增加被LS降低所取代，并且局部缺血期间突然的LS反转消失。虽然LS信号在SD和局部缺血期间表现出不同的特征，但DC电位总是呈现负向偏移，ECS体积总是表现出相似的减小。这些结果表明，LS信号的极性由至少两个因素的竞争决定：细胞肿胀和阴离子内流。
