NADH fluorescence imaging and the histological impact of cortical spreading depolarization during the acute phase of subarachnoid hemorrhage in rats

Abstract

OBJECTIVEAlthough cortical spreading depolarization (CSD) has been observed during the early phase of subarachnoid hemorrhage (SAH) in clinical settings, the pathogenicity of CSD is unclear. The aim of this study is to elucidate the effects of loss of membrane potential on neuronal damage during the acute phase of SAH.METHODSTwenty-four rats were subjected to SAH by the perforation method. The propagation of depolarization in the brain cortex was examined by using electrodes to monitor 2 direct-current (DC) potentials and obtaining NADH (reduced nicotinamide adenine dinucleotide) fluorescence images while exposing the parietal-temporal cortex to ultraviolet light. Cerebral blood flow (CBF) was monitored in the vicinity of the lateral electrode. Twenty-four hours after onset of SAH, histological damage was evaluated at the DC potential recording sites.RESULTSChanges in DC potentials (n = 48 in total) were sorted into 3 types according to the appearance of ischemic depolarization in the entire hemisphere following induction of SAH. In Type 1 changes (n = 21), ischemic depolarization was not observed during a 1-hour observation period. In Type 2 changes (n = 13), the DC potential demonstrated ischemic depolarization on initiation of SAH and recovered 80% from the maximal DC deflection during a 1-hour observation period (33.3 ± 15.8 minutes). In Type 3 changes (n = 14), the DC potential displayed ischemic depolarization and did not recover during a 1-hour observation period. Histological evaluations at DC potential recording sites showed intact tissue at all sites in the Type 1 group, whereas in the Type 2 and Type 3 groups neuronal damage of varying severity was observed depending on the duration of ischemic depolarization. The duration of depolarization that causes injury to 50% of neurons (P50) was estimated to be 22.4 minutes (95% confidence intervals 17.0–30.3 minutes). CSD was observed in 3 rats at 6 sites in the Type 1 group 5.1 ± 2.2 minutes after initiation of SAH. On NADH fluorescence images CSD was initially observed in the anterior cortex; it propagated through the entire hemisphere in the direction of the occipital cortex at a rate of 3 mm/minute, with repolarization in 2.3 ± 1.2 minutes. DC potential recording sites that had undergone CSD were found to have intact tissue 24 hours later. Compared with depolarization that caused 50% neuronal damage, the duration of CSD was too short to cause histological damage.CONCLUSIONSCSD was successfully visualized using NADH fluorescence. It propagated from the anterior to the posterior cortex along with an increase in CBF. The duration of depolarization in CSD (2.3 ± 1.2 minutes) was far shorter than that causing 50% neuronal damage (22.4 minutes) and was not associated with histological damage in the current experimental setting.

Depolarization time and extracellular glutamate levels aggravate ultra-early brain injury after subarachnoid hemorrhage

“…In a previous study, the duration of depolarization was signi cantly correlated with the severity of neurological injury 10 . The results of Experiment 1 also indicated that the duration of depolarization has a strong impact on the aggravation of the neuronal injury.…”

“…It is known that in the acute-phase of SAH, intracranial pressure (ICP) and cerebral blood ow (CBF) changes dynamically, resulting in excessive release of excitatory amino acids such as glutamate, which causes neuronal damage 9 . Shimizu et al divided the changes in extracellular potentials into three types, and showed that the duration of depolarization was signi cantly correlated with the severity of neurological injury in a rat perforation model 10 . They also revealed that the duration of depolarization that caused 50% of neuronal damage was estimated to be 22.4 min, and hypothesized that controlling the ICP within the rst hour after SAH was important for brain protection.…”

The blood–brain barrier and the neurovascular unit in subarachnoid hemorrhage: molecular events and potential treatments

“…It has been found that CSD begins 1 ± 2.2 min after SAH induction of and repolarization occurs within 2.3 ± 1.2 min. The direction of CSD is from the frontal lobe cortex in the direction of the occipital lobe cortex at a rate of 3 mm per minute [ 466 ]. CSD is a multifactorial phenomenon with some degree of contribution from glutamate, ATP, extracellular K + release, intracellular Ca 2+ accumulation, as well as local anoxia [ 332 ].…”

Spreading Depolarizations and Subarachnoid Hemorrhage

“…The observational studies have established that SDs following SAH can be detected using electrocorticography (ECoG) [24,39], extracellular potassium recording [40], MRI [41,42,44], and cerebral blood flow and NADH imaging [43]. These studies also determined the sequelae of SDs in the setting of SAH by infarct volume on histology, activity of the Na + /K + ATPase, and mortality and functional outcomes.…”