The impact of aging on spreading depolarization in the intact and ischemic rat brain

Background: Aging emerges as a major independent risk factor for the incidence and prevalence of ischemic stroke and predicts poor patient outcomes. In our aging population, much of the primary injury in the acute phase of ischemic stroke may prove irreversible, yet the management of secondary pathophysiological processes is of fundamental importance to improve the prospect of successful recovery. Spontaneously occurring recurrent spreading depolarizations (SDs) were recognized as contributors of the expansion of cerebral tissue damage following subarachnoid hemorrhage, stroke or traumatic brain injury. Hypothesis: Since the aged brain is more susceptible to ischemia- and SD-related injury, we hypothesized, that (1) the evolution of SDs and the related hemodynamic responses could be altered by aging and (2) the SD associated metabolic changes, such as tissue acidosis should also be graver in the aged ischemic brain. Aims: We set out to determine; (1) the impact of age on the evolution of SD and the kinetics of the associated changes in local CBF in the intact and ischemic rat brain, (2) the impact of age on the SD related tissue pH changes in the intact and ischemic rat brain, and (3) the association between the SD-related pH transients and SD-related CBF responses. Methods: Open or closed cranial windows were mounted on the parietal bone of halothane or isoflurane-anesthetized young (2-months-, n=33) and old (18-20-month-old, n=18, and 2-year-old, n= 26) Sprague Dawley or Wistar rats. Mean arterial blood pressure and arterial blood gases were monitored via a femoral artery catheter. Transient incomplete global forebrain ischemia was achieved by the bilateral occlusion of the common carotid arteries (2VO). SDs were elicited by the topical application of KCl. The evolution of SDs and –the associated local CBF changes were acquired by the measurement of DC potential and laser-Doppler flowmetry. SD-related variations in extracellular pH were acquired with pH-sensitive microelectrodes inserted into the cortex. SD-coupled intracellular pH- and perfusion changes were monitored relying on the fluorescence intensity of a pH indicator dye (Neutral Red), and laser speckle contrast analysis, respectively. Results: Ischemia elongated the duration of the SD-related negative DC shift (66.2±22.8 vs. 21.4±4.1 s, Young 2VO vs. Young control), which was augmented further by age as seen in the Old 2VO group (95.8±46.2 s). Six types of SD-coupled CBF responses were identified, ranging from dominating hyperemia to prolonged cortical spreading ischemia with intermediate forms. Spreading ischemia evolved only in the aged ischemic group (4 of the 6 animals). Quantitative analysis of the duration of early hypoperfusion indicated that this first element of the CBF response to SD was elongated during ischemia (36.8±17.5 vs. 7.9±6.8 sec, Young 2VO vs. Young control) and became drastically longer in the Old 2VO group (1344±1047 sec), due to the prevalence of spreading ischemia. Acid accumulation with SDs propagating across the ischemic cortex was considerably increased with respect to the intact and reperfused condition (e.g. relative amplitude of acidosis: pH 0.43±0.15 vs. 0.36±0.07 vs. 0.31±0.09, ischemia vs. intact vs. reperfused). Tissue acidosis with SD was additive to ischemia-induced acidosis thereby raising acid load to potentially cytotoxic levels (level of acidosis: pH 6.48±0.16 vs. 6.93±0.09, with SD under ischemia vs. ischemia alone prior to SD onset). In addition, tissue pH remained acidic for at least 10 min after the passage of an SD (pH 7.09±0.09 vs. 7.29±0.16, 12 min after SD vs. time control ischemia without SD), which was further deepened in the aged brain (pH 6.94±0.08 vs. 7.09±0.09, old vs. young). Discussion: While ischemia clearly compromised the kinetics of SDs and the associated CBF response, age exerted an additional shift to more injurious CBF response types including spreading ischemia. We propose that structural and functional alteration of the cerebro-microvascular system with aging serves as a potential basis for compromised vascular reactivity. The prospect of successful recovery after stroke strongly depends on the metabolic statement of the affected tissue. Marked tissue acidosis correlates with the extent of brain injury, and has been traditionally considered as a damaging component of cerebral ischemia. In conclusion, SDs are suggested to extend ischemic lesions by increasing acid accumulation in the ischemic penumbra to toxic levels characteristic of the ischemic core. Repeated SDs typically evolving in the ischemic cortex are expected to maintain low pH, which decreases the threshold of acid-induced cell death. Finally, the aged brain may be at higher risk for SD-related injury, because the recovery of tissue pH after SD is hampered

Nimodipine augments cerebrovascular reactivity in aging but runs the risk of local perfusion reduction in acute cerebral ischemia

IntroductionThe efficacy of cerebrovascular reactivity (CVR) is taken as an indicator of cerebrovascular health.Methods and ResultsWe found that CVR tested with the inhalation of 10 % CO2 declined in the parietal cortex of 18-20-month-old rats. The CVR deficit in old rats was coincident with cerebrovascular smooth muscle cell and astrocyte senescence, revealed by the immuno-labeling of the cellular senescence marker p16 in these cells. In a next series of experiments, CVR was severely impaired in the acute phase of incomplete global forebrain ischemia produced by the bilateral occlusion of the common carotid arteries in young adult rats. In acute ischemia, CVR impairment often manifested as a perfusion drop rather than blood flow elevation in response to hypercapnia. Next, nimodipine, an L-type voltage-gated calcium channel antagonist was administered topically to rescue CVR in both aging, and cerebra ischemia. Nimodipine augmented CVR in the aged brain, but worsened CVR impairment in acute cerebral ischemia.DiscussionA careful evaluation of benefits and side effects of nimodipine is recommended, especially in acute ischemic stroke

Spectral and Multifractal Signature of Cortical Spreading Depolarisation in Aged Rats

Cortical spreading depolarisation (CSD) is a transient disruption of ion balance that propagates along the cortex. It has been identified as an important factor in the progression of cerebral damage associated with stroke or traumatic brain injury. We analysed local field potential signals during CSD in old and young rats to look for age-related differences. We compared CSDs elicited under physiological conditions (baseline), during ischaemia and during reperfusion. We applied short-time Fourier transform and a windowed implementation of multifractal detrended fluctuation analysis to follow the electrophysiological signature of CSD. Both in the time-dependent spectral profiles and in the multifractal spectrum width, CSDs appeared as transient dips, which we described on the basis of their duration, depression and recovery slope and degree of drop and rise. The most significant age-related difference we found was in the depression slope, which was significantly more negative in the beta band and less negative in the delta band of old animals. In several parameters, we observed an attenuation-regeneration pattern in reaction to ischaemia and reperfusion, which was absent in the old age group. The age-related deviation from the pattern took two forms: the rise parameter did not show any attenuation in ischaemic conditions for old animals, whilst the depression slope in most frequency bands remained attenuated during reperfusion and did not regenerate in this age group. Though the multifractal spectrum width proved to be a reliable indicator of events like CSDs or ischaemia onset, we failed to find any case where it would add extra detail to the information provided by the Fourier description

Spreading depolarization causes reperfusion failure after cerebral ischemia

Despite successful recanalization, reperfusion failure associated with poor neurological outcomes develops in half of treated stroke patients. We explore here whether spreading depolarization (SD) is a predictor of reperfusion failure. Global forebrain ischemia/reperfusion was induced in male and female C57BL/6 mice (n = 57). SD and cerebral blood flow (CBF) changes were visualized with transcranial intrinsic optical signal and laser speckle contrast imaging. To block SD, MK801 was applied (n = 26). Neurological deficit, circle of Willis (CoW) anatomy and neuronal injury were evaluated 24 hours later. SD emerged after ischemia onset in one or both hemispheres under a perfusion threshold (CBF drop to 21.1 ± 4.6 vs. 33.6 ± 4.4%, SD vs. no SD). The failure of later reperfusion (44.4 ± 12.5%) was invariably linked to previous SD. In contrast, reperfusion was adequate (98.9 ± 7.4%) in hemispheres devoid of SD. Absence of the P1 segment of the posterior cerebral artery in the CoW favored SD occurrence and reperfusion failure. SD occurrence and reperfusion failure were associated with poor neurologic function, and neuronal necrosis 24 hours after ischemia. The inhibition of SD significantly improved reperfusion. SD occurrence during ischemia impairs later reperfusion, prognosticating poor neurological outcomes. The increased likelihood of SD occurrence is predicted by inadequate collaterals

Spreading depolarization remarkably exacerbates ischemia-induced tissue acidosis in the young and aged rat brain

Spreading depolarizations (SDs) occur spontaneously in the cerebral cortex of subarachnoid hemorrhage, stroke or traumatic brain injury patients. Accumulating evidence prove that SDs exacerbate focal ischemic injury by converting zones of the viable but non-functional ischemic penumbra to the core region beyond rescue. Yet the SD-related mechanisms to mediate neurodegeneration remain poorly understood. Here we show in the cerebral cortex of isoflurane-anesthetized, young and old laboratory rats, that SDs propagating under ischemic penumbra-like conditions decrease intra and- extracellular tissue pH transiently to levels, which have been recognized to cause tissue damage. Further, tissue pH after the passage of each spontaneous SD event remains acidic for over 10 minutes. Finally, the recovery from SD-related tissue acidosis is hampered further by age. We propose that accumulating acid load is an effective mechanism for SD to cause delayed cell death in the ischemic nervous tissue, particularly in the aged brain

Advancing age and ischemia elevate the electric threshold to elicit spreading depolarization in the cerebral cortex of young adult rats

Spreading depolarizations of long cumulative duration have been implicated in lesion development and progression in patients with stroke and traumatic brain injury. Spreading depolarizations evolve less likely in the aged brain, but it remains to be determined at what age the susceptibility to spreading depolarizations starts to decline, especially in ischemia. Spreading depolarizations were triggered by epidural electric stimulation prior and after ischemia induction in the cortex of 7–30 weeks old anesthetized rats ( n = 38). Cerebral ischemia was achieved by occlusion of both common carotid arteries. Spreading depolarization occurrence was confirmed by the acquisition of DC potential and electrocorticogram. Cerebral blood flow variations were recorded by laser-Doppler flowmetry. Dendritic spine density in the cortex was determined in Golgi-COX stained sections. Spreading depolarization initiation required increasingly greater electric charge with older age, a potential outcome of consolidation of cortical connections, indicated by altered dendritic spine distribution. The threshold of spreading depolarization elicitation increased with ischemia in all age groups, which may be caused by tissue acidosis and increased K+ conductance, among other factors. In conclusion, the brain appears to be the most susceptible to spreading depolarizations at adolescent age; therefore, spreading depolarizations may occur in young patients of ischemic or traumatic brain injury at the highest probability. </jats:p

Transient Hypoperfusion to Ischemic/Anoxic Spreading Depolarization is Related to Autoregulatory Failure in the Rat Cerebral Cortex

BACKGROUND: In ischemic stroke, cerebral autoregulation and neurovascular coupling may become impaired. The cerebral blood flow (CBF) response to spreading depolarization (SD) is governed by neurovascular coupling. SDs recur in the ischemic penumbra and reduce neuronal viability by the insufficiency of the CBF response. Autoregulatory failure and SD may coexist in acute brain injury. Here, we set out to explore the interplay between the impairment of cerebrovascular autoregulation, SD occurrence, and the evolution of the SD-coupled CBF response. METHODS: Incomplete global forebrain ischemia was created by bilateral common carotid artery occlusion in isoflurane-anesthetized rats, which induced ischemic SD (iSD). A subsequent SD was initiated 20–40 min later by transient anoxia SD (aSD), achieved by the withdrawal of oxygen from the anesthetic gas mixture for 4–5 min. SD occurrence was confirmed by the recording of direct current potential together with extracellular K(+) concentration by intracortical microelectrodes. Changes in local CBF were acquired with laser Doppler flowmetry. Mean arterial blood pressure (MABP) was continuously measured via a catheter inserted into the left femoral artery. CBF and MABP were used to calculate an index of cerebrovascular autoregulation (rCBFx). In a representative imaging experiment, variation in transmembrane potential was visualized with a voltage-sensitive dye in the exposed parietal cortex, and CBF maps were generated with laser speckle contrast analysis. RESULTS: Ischemia induction and anoxia onset gave rise to iSD and aSD, respectively, albeit aSD occurred at a longer latency, and was superimposed on a gradual elevation of K(+) concentration. iSD and aSD were accompanied by a transient drop of CBF (down to 11.9 ± 2.9 and 7.4 ± 3.6%, iSD and aSD), but distinctive features set the hypoperfusion transients apart. During iSD, rCBFx indicated intact autoregulation (rCBFx  0.3) because CBF followed the decreasing MABP. CBF dropped 15–20 s after iSD, but the onset of hypoperfusion preceded aSD by almost 3 min. Taken together, the CBF response to iSD displayed typical features of spreading ischemia, whereas the transient CBF reduction with aSD appeared to be a passive decrease of CBF following the anoxia-related hypotension, leading to aSD. CONCLUSIONS: We propose that the dysfunction of cerebrovascular autoregulation that occurs simultaneously with hypotension transients poses a substantial risk of SD occurrence and is not a consequence of SD. Under such circumstances, the evolving SD is not accompanied by any recognizable CBF response, which indicates a severely damaged neurovascular coupling

A multimodális posztoperatív fájdalomcsillapítás szerepe primer csípőízületi arthroplasticában

Absztrakt: Bevezetés: Az egyre nagyobb számban végzett nagyízületi arthroplasticák miatt előtérbe került a posztoperatív kórházi napok számának csökkentése, valamint a rehabilitáció gyorsítása. Ehhez elengedhetetlen a megfelelő, hatékony, biztonságos posztoperatív fájdalomcsillapítás. Célkitűzés: Vizsgálatunk célja az volt, hogy összehasonlítsuk a hagyományos és az újfajta multimodális fájdalomcsillapító kezelésben részesült betegek posztoperatív funkcionális eredményeit, a műtétet követő fájdalomszintjüket és opioidfájdalomcsillapító-igényeiket. Módszer: Prospektív vizsgálatunkba 81 beteget vontunk be, akiknél 2017. február és 2018. január között intézetünkben primer csípőprotézis-implantációt végeztünk. A randomizált módon csoportosított betegek közül a kontrollcsoportban 38 fő, a multimodális fájdalomcsillapításban részesült betegek csoportjában 43 fő szerepelt. Vizuális analóg skála (VAS) segítségével ellenőriztük a betegek szubjektív fájdalomszintjét, valamint rögzítettük fájdalomcsillapító-igényüket. Eredmények: Multimodális fájdalomcsillapításban részesült betegeinknél az opioidtartalmú fájdalomcsillapítók iránti szignifikánsan alacsonyabb igényt, valamint szignifikánsan alacsonyabb VAS-értéket tapasztaltunk a posztoperatív 6. órában, 3. és 4. napon. Továbbá e csoport betegei szignifikánsan rövidebb ideig tartózkodtak a kórházban a műtétet követően. Következtetések: Tapasztalataink alapján a multimodális fájdalomcsillapítás egyoldali primer csípőízületi arthroplastica esetén szignifikánsan csökkentette a betegek posztoperatív szubjektív fájdalomérzetét és fájdalomcsillapító-igényét. Orv Hetil. 2019; 160(52): 2054–2060. | Abstract: Introduction: Due to the increasing number of arthroplasties, the number of post-operative hospital days was reduced and the rate of rehabilitation accelerated. For this, proper postoperative analgesia is essential and the multimodal pain relief is an excellent tool. Aim: The aim of our study was to compare postoperative functional results, postoperative pain levels, and opioid analgesic needs of patients who received conventional and novel analgesic treatments. Method: In our prospective study, 81 patients were enrolled who underwent primary hip prosthesis surgery in our institution between February 2017 and January 2018. Of the randomized patients, 38 were in the control group and 43 in the multimodal pain group. We have tested their analgesic needs and the subjective pain levels of patients with the help of the visual analog scale (VAS). Results: Patients receiving multimodal pain relief had significantly lower opioid analgesic requirements and significantly lower VAS values assessed at 6 hours, and 3 and 4 days postoperatively. In addition, the patients in this group stayed in the hospital for a significantly shorter time after surgery. Conclusions: Based on our experience, multimodal pain relief in one-sided primary hip joint arthroplasty significantly reduced the patients’ postoperative subjective pain sensation and pain killer consumptions. Orv Hetil. 2019; 160(52): 2054–2060

Astrocyte Ca2+ Waves and Subsequent Non-Synchronized Ca2+ Oscillations Coincide with Arteriole Diameter Changes in Response to Spreading Depolarization

Spreading depolarization (SD) is a wave of mass depolarization that causes profound perfusion changes in acute cerebrovascular diseases. Although the astrocyte response is secondary to the neuronal depolarization with SD, it remains to be explored how glial activity is altered after the passage of SD. Here, we describe post-SD high frequency astrocyte Ca2+ oscillations in the mouse somatosensory cortex. The intracellular Ca2+ changes of SR101 labeled astrocytes and the SD-related arteriole diameter variations were simultaneously visualized by multiphoton microscopy in anesthetized mice. Post-SD astrocyte Ca2+ oscillations were identified as Ca2+ events non-synchronized among astrocytes in the field of view. Ca2+ oscillations occurred minutes after the Ca2+ wave of SD. Furthermore, fewer astrocytes were involved in Ca2+ oscillations at a given time, compared to Ca2+ waves, engaging all astrocytes in the field of view simultaneously. Finally, our data confirm that astrocyte Ca2+ waves coincide with arteriolar constriction, while post-SD Ca2+ oscillations occur with the peak of the SD-related vasodilation. This is the first in vivo study to present the post-SD astrocyte Ca2+ oscillations. Our results provide novel insight into the spatio-temporal correlation between glial reactivity and cerebral arteriole diameter changes behind the SD wavefront