Safety, hemodynamic effects, and detection of acute xenon inhalation: rationale for banning xenon from sport

This study aimed to quantify the sedative effects, detection rates, and cardiovascular responses to xenon. On 3 occasions, participants breathed xenon (FiXe 30% for 20 min; FiXe 50% for 5 min; FiXe 70% for 2 min) in a nonblinded design. Sedation was monitored by a board-certified anesthesiologist. During 70% xenon, participants were also verbally instructed to operate a manual value with time-to-task failure being recorded. Beat-by-beat hemodynamics were measured continuously by ECG, photoplethysmography, and transcranial Doppler. Over 48 h postadministration, xenon was measured in blood and urine by gas chromatography-mass spectrometry. Xenon caused variable levels of sedation and restlessness. Task failure of the self-operating value occurred at 60–90 s in most individuals. Over the first minute, 50% and 70% xenon caused a substantial reduction in total peripheral resistance ( P < 0.05). All dosages caused an increase in cardiac output ( P < 0.05). By the end of xenon inhalation, slight hypertension was observed after all three doses ( P < 0.05), with an increase in middle cerebral artery velocity ( P < 0.05). Xenon was consistently detected, albeit in trace amounts, up to 3 h after all three doses of xenon inhalation in blood and urine with variable results thereafter. Xenon inhalation caused sedation incompatible with self-operation of a breathing apparatus, thus causing a potential life-threatening condition in the absence of an anesthesiologist. Yet, xenon can only be reliably detected in blood and urine up to 3 h postacute dosing.

NEW & NOTEWORTHY Breathing xenon in dosages conceivable for doping purposes (FiXe 30% for 20 min; FiXe 50% for 5 min; FiXe 70% for 2 min) causes an initial rapid fall in total peripheral resistance with tachycardia and thereafter a mild hypertension with elevated middle cerebral artery velocity. These dose duration intervals cause sedation that is incompatible with operating a breathing apparatus and can only be detected in blood and urine samples with a high probability for up to ~3 h.

General Anesthesia: A Probe to Explore Consciousness

General anesthesia reversibly alters consciousness, without shutting down the brain globally. Depending on the anesthetic agent and dose, it may produce different consciousness states including a complete absence of subjective experience (unconsciousness), a conscious experience without perception of the environment (disconnected consciousness, like during dreaming), or episodes of oriented consciousness with awareness of the environment (connected consciousness). Each consciousness state may potentially be followed by explicit or implicit memories after the procedure. In this respect, anesthesia can be considered as a proxy to explore consciousness. During the recent years, progress in the exploration of brain function has allowed a better understanding of the neural correlates of consciousness, and of their alterations during anesthesia. Several changes in functional and effective between-region brain connectivity, consciousness network topology, and spatio-temporal dynamics of between-region interactions have been evidenced during anesthesia. Despite a set of effects that are common to many anesthetic agents, it is still uneasy to draw a comprehensive picture of the precise cascades during general anesthesia. Several questions remain unsolved, including the exact identification of the neural substrate of consciousness and its components, the detection of specific consciousness states in unresponsive patients and their associated memory processes, the processing of sensory information during anesthesia, the pharmacodynamic interactions between anesthetic agents, the direction-dependent hysteresis phenomenon during the transitions between consciousness states, the mechanisms of cognitive alterations that follow an anesthetic procedure, the identification of an eventual unitary mechanism of anesthesia-induced alteration of consciousness, the relationship between network effects and the biochemical or sleep-wake cycle targets of anesthetic agents, as well as the vast between-studies variations in dose and administration mode, leading to difficulties in between-studies comparisons. In this narrative review, we draw the picture of the current state of knowledge in anesthesia-induced unconsciousness, from insights gathered on propofol, halogenated vapors, ketamine, dexmedetomidine, benzodiazepines and xenon. We also describe how anesthesia can help understanding consciousness, we develop the above-mentioned unresolved questions, and propose tracks for future research.

Purine nucleoside use as surrogate markers of cerebral ischaemia during local and general anaesthetic carotid endarterectomy

Objectives:

In periods of cerebral ischaemia, adenosine triphosphate is metabolised, leading to accumulation of adenosine inosine and hypoxanthine. These can be measured in real time using peripheral blood samples intraoperatively. The primary aim of this study was to describe changes in purine concentrations in a cohort of patients undergoing carotid endarterectomy under general anaesthetic, and to evaluate correlation between changes in values with major perioperative steps. The secondary aim was to compare changes in concentrations with a previous cohort of patients who had undergone carotid endarterectomy under local anaesthetic.

Methods:

This was a prospective observational study. Purine concentrations were determined from arterial line samples and measured via an amperometric biosensor at specific time points during carotid endarterectomy. Mean arterial pressure was manipulated to maintain steady cerebral perfusion pressure throughout the procedure. These results were analysed against data from a cohort of patients who underwent carotid endarterectomy under local anaesthetic in previously published work.

Results:

Valid results were obtained for 37 patients. Purine concentrations at baseline were 3.02 ± 1.11 µM and 3.16 ± 1.85 µM for the unshunted and shunted cohorts, respectively. There was no significant change after 30 min of carotid clamping at 2.07 ± 0.89 and 2.4 ± 3.09 µM, respectively (both p > 0.05). Peak purine during the clamp phase in the loco-regional anaesthetic cohort was 6.70 ± 3.4 µM, which was significantly raised compared to both general anaesthetic cohorts (p = 0.004). There were no perioperative neurological events in either cohort.

Conclusion:

This small study does not demonstrate conclusive evidence that purine nucleosides can be used as a marker of cerebral ischaemia; the comparisons to the loco-regional anaesthetic data offer information about differences in the cerebral adenosine triphosphate metabolism between general anaesthetic and loco-regional anaesthetic. We hypothesise that the lack of a rise in purine nucleosides under general anaesthetic may be caused by a decrease in the cerebral metabolic rate and loss of metabolic rate-blood flow coupling caused by general anaesthetic agents.

Effects of anesthesia on cerebral blood flow, metabolism, and neuroprotection

Administration of anesthetic agents fundamentally shifts the responsibility for maintenance of homeostasis from the patient and their intrinsic physiological regulatory mechanisms to the anesthesiologist. Continuous delivery of oxygen and nutrients to the brain is necessary to prevent irreversible injury and arises from a complex series of regulatory mechanisms that ensure uninterrupted cerebral blood flow. Our understanding of these regulatory mechanisms and the effects of anesthetics on them has been driven by the tireless work of pioneers in the field. It is of paramount importance that the anesthesiologist shares this understanding. Herein, we will review the physiological determinants of cerebral blood flow and how delivery of anesthesia impacts these processes.

Recording Brain Electromagnetic Activity During the Administration of the Gaseous Anesthetic Agents Xenon and Nitrous Oxide in Healthy Volunteers

Anesthesia arguably provides one of the only systematic ways to study the neural correlates of global consciousness/unconsciousness. However to date most neuroimaging or neurophysiological investigations in humans have been confined to the study of γ-Amino-Butyric-Acid-(GABA)-receptor-agonist-based anesthetics, while the effects of dissociative N-Methyl-D-Aspartate-(NMDA)-receptor-antagonist-based anesthetics ketamine, nitrous oxide (N2O) and xenon (Xe) are largely unknown. This paper describes the methods underlying the simultaneous recording of magnetoencephalography (MEG) and electroencephalography (EEG) from healthy males during inhalation of the gaseous anesthetic agents N2O and Xe. Combining MEG and EEG data enables the assessment of electromagnetic brain activity during anesthesia at high temporal, and moderate spatial, resolution. Here we describe a detailed protocol, refined over multiple recording sessions, that includes subject recruitment, anesthesia equipment setup in the MEG scanner room, data collection and basic data analysis. In this protocol each participant is exposed to varying levels of Xe and N2O in a repeated measures cross-over design. Following relevant baseline recordings participants are exposed to step-wise increasing inspired concentrations of Xe and N2O of 8, 16, 24 and 42%, and 16, 32 and 47% respectively, during which their level of responsiveness is tracked with an auditory continuous performance task (aCPT). Results are presented for a number of recordings to highlight the sensor-level properties of the raw data, the spectral topography, the minimization of head movements, and the unequivocal level dependent effects on the auditory evoked responses. This paradigm describes a general approach to the recording of electromagnetic signals associated with the action of different kinds of gaseous anesthetics, which can be readily adapted to be used with volatile and intravenous anesthetic agents. It is expected that the method outlined can contribute to the understanding of the macro-scale mechanisms of anesthesia by enabling methodological extensions involving source space imaging and functional network analysis.

Xenon as an adjuvant to sevoflurane anesthesia in children younger than 4 years of age, undergoing interventional or diagnostic cardiac catheterization: A randomized controlled clinical trial

BACKGROUND

Xenon has repeatedly been demonstrated to have only minimal hemodynamic side effects when compared to other anesthetics. Moreover, in experimental models, xenon was found to be neuroprotective and devoid of developmental neurotoxicity. These properties could render xenon attractive for the anesthesia in neonates and infants with congenital heart disease. However, experience with xenon anesthesia in children is scarce.

AIMS

We hypothesized that in children undergoing cardiac catheterization, general anesthesia with a combination of sevoflurane with xenon results in superior hemodynamic stability, compared to sevoflurane alone.

METHODS

In this prospective, randomized, single-blinded, controlled clinical trial, children with a median age of 12 [IQR 3-36] months undergoing diagnostic/interventional cardiac catheterization were randomized to either general anesthesia with 50-65vol% xenon plus sevoflurane or sevoflurane alone. The primary outcome was the incidence of intraprocedural hemodynamic instability, defined as the occurrence of: (i) a heart rate change >20% from baseline; or (ii) a change in mean arterial blood pressure >20% from baseline; or (iii) the requirement of vasopressors, inotropes, chronotropes, or fluid boluses. Secondary endpoints included recovery characteristics, feasibility criteria, and safety (incidence of emergence agitation and postoperative vomiting.

RESULTS

After inclusion of 40 children, the trial was stopped as an a priori planned blinded interim analysis revealed that the overall rate of hemodynamic instability did not differ between groups [100% in both the xenon-sevoflurane and the sevoflurane group. However, the adjuvant administration of xenon decreased vasopressor requirements, preserved better cerebral oxygen saturation, and resulted in a faster recovery. Xenon anesthesia was feasible (with no differences in the need for rescue anesthetics in both groups).

CONCLUSION

Our observations suggest that combining xenon with sevoflurane in preschool children is safe, feasible, and facilitates hemodynamic management. Larger and adequately powered clinical trials are warranted to investigate the impact of xenon on short- and long-term outcomes in pediatric anesthesia.

Hypometabolism as the ultimate defence in stress response: how the comparative approach helps understanding of medically relevant questions

First conceptualized from breath-hold diving mammals, later recognized as the ultimate cell autonomous survival strategy in anoxia-tolerant vertebrates and burrowing or hibernating rodents, hypometabolism is typically recruited by resilient organisms to withstand and recover from otherwise life-threatening hazards. Through the coordinated down-regulation of biosynthetic, proliferative and electrogenic expenditures at times when little ATP can be generated, a metabolism turned 'down to the pilot light' allows the re-balancing of energy demand with supply at a greatly suppressed level in response to noxious exogenous stimuli or seasonal endogenous cues. A unifying hallmark of stress-tolerant organisms, the adaptation effectively prevents lethal depletion of ATP, thus delineating a marked contrast with susceptible species. Along with disengaged macromolecular syntheses, attenuated transmembrane ion shuttling and PO₂ -conforming respiration rates, the metabolic slowdown in tolerant species usually culminates in a non-cycling, quiescent phenotype. However, such a reprogramming also occurs in leading human pathophysiologies. Ranging from microbial infections through ischaemia-driven infarcts to solid malignancies, cells involved in these disorders may again invoke hypometabolism to endure conditions non-permissive for growth. At the same time, their reduced activities underlie the frequent development of a general resistance to therapeutic interventions. On the other hand, a controlled induction of hypometabolic and/or hypothermic states by pharmacological means has recently stimulated intense research aimed at improved organ preservation and patient survival in situations requiring acutely administered critical care. The current review article therefore presents an up-to-date survey of concepts and applications of a coordinated and reversibly down-regulated metabolic rate as the ultimate defence in stress responses.

Xenon for the prevention of postoperative delirium in cardiac surgery: study protocol for a randomized controlled clinical trial

Background

Postoperative delirium (POD) is a manifestation of acute postoperative brain dysfunction that is frequently observed after cardiac surgery. POD is associated with short-term complications such as an increase in mortality, morbidity, costs and length of stay, but can also have long-term sequelae, including persistent cognitive deficits, loss of independence, and increased mortality for up to 2 years. The noble gas xenon has been demonstrated in various models of neuronal injury to exhibit remarkable neuroprotective properties. We therefore hypothesize that xenon anesthesia reduces the incidence of POD in elderly patients undergoing cardiac surgery with the use of cardiopulmonary bypass.

Methods/Design

One hundred and ninety patients, older than 65 years, and scheduled for elective cardiac surgery, will be enrolled in this prospective, randomized, controlled trial. Patients will be randomized to receive general anesthesia with either xenon or sevoflurane. Primary outcome parameter will be the incidence of POD in the first 5 postoperative days. The occurrence of POD will be assessed by trained research personnel, blinded to study group, with the validated 3-minute Diagnostic Confusion Assessment Method (3D-CAM) (on the intensive care unit in its version specifically adapted for the ICU), in addition to chart review and the results of delirium screening tools that will be performed by the bedside nurses). Secondary outcome parameters include duration and severity of POD, and postoperative cognitive function as assessed with the Mini-Mental State Examination.

Discussion

Older patients undergoing cardiac surgery are at particular risk to develop POD. Xenon provides remarkable hemodynamic stability and has been suggested in preclinical studies to exhibit neuroprotective properties. The present trial will assess whether the promising profile of xenon can be translated into a better outcome in the geriatric population.

Trial registration

EudraCT Identifier: 2014-005370-11 (13 May 2015).

Alpha-lipoic acid treatment is neurorestorative and promotes functional recovery after stroke in rats

The antioxidant properties of alpha-lipoic acid (aLA) correlate with its ability to promote neuroproliferation. However, there have been no comprehensive studies examining the neurorestorative effects of aLA administration after the onset of ischemia. The middle cerebral artery (MCA) of adult rats was occluded for 2 hours and then reperfused. aLA (20 mg/kg) was administered in 71 animals (aLA group) through the left external jugular vein immediately after reperfusion. An equivalent volume of vehicle was administered to 71 animals (control group). Functional outcome, levels of endogenous neural precursors with neurogenesis, glial cell activation, and brain metabolism were evaluated. Immediate aLA administration after reperfusion resulted in significantly reduced mortality, infarct size, and neurological deficit score (NDS) in the test group compared to the control group. Long-term functional outcomes, measured by the rotarod test, were markedly improved by aLA treatment. There was a significant increase in the number of cells expressing nestin and GFAP in the boundary zone and infarct core regions after aLA treatment. Furthermore, significantly more BrdU/GFAP, BrdU/DCX, and BrdU/NeuN double-labeled cells were observed along the boundary zone of the aLA group on days 7, 14, and 28 days, respectively. And brain metabolism using ¹⁸F-FDG microPET imaging was markedly improved in aLA group. The effects of aLA was blocked by insulin receptor inhibitor, HNMPA (AM)3. These results indicate that immediate treatment with aLA after ischemic injury may have significant neurorestorative effects mediated at least partially via insulin receptor activation. Thus, aLA may be useful for the treatment of acute ischemic stroke.

Effects of xenon and hypothermia on cerebrovascular pressure reactivity in newborn global hypoxic-ischemic pig model

Autoregulation of cerebral perfusion is impaired in hypoxic-ischemic encephalopathy. We investigated whether cerebrovascular pressure reactivity (PRx), an element of cerebral autoregulation that is calculated as a moving correlation coefficient between averages of intracranial and mean arterial blood pressure (MABP) with values between -1 and +1, is impaired during and after a hypoxic-ischemic insult (HI) in newborn pigs. Associations between end-tidal CO2, seizures, neuropathology, and PRx were investigated. The effect of hypothermia (HT) and Xenon (Xe) on PRx was studied. Pigs were randomized to Sham, and after HI to normothermia (NT), HT, Xe or xenon hypothermia (XeHT). We defined PRx >0.2 as peak and negative PRx as preserved. Neuropathology scores after 72 hours of survival was grouped as 'severe' or 'mild.' Secondary PRx peak during recovery, predictive of severe neuropathology and associated with insult severity (P=0.05), was delayed in HT (11.5 hours) than in NT (6.5 hours) groups. Seizures were associated with impaired PRx in NT pigs (P=0.0002), but not in the HT/XeHT pigs. PRx was preserved during normocapnia and impaired during hypocapnia. Xenon abolished the secondary PRx peak, increased (mean (95% confidence interval (CI)) MABP (6.5 (3.8, 9.4) mm Hg) and cerebral perfusion pressure (5.9 (2.9, 8.9) mm Hg) and preserved the PRx (regression coefficient, -0.098 (95% CI (-0.18, -0.01)), independent of the insult severity.

Xenon consumption during general surgery: a retrospective observational study

BACKGROUND

High costs still limits the widespread use of xenon in the clinical practice. Therefore, we evaluated xenon consumption of different delivery modes during general surgery.

METHODS

A total of 48 patients that underwent general surgery with balanced xenon anaesthesia were retrospectively analysed according to the mode of xenon delivery during maintenance phase (ECO mode, AUTO mode or MANUAL mode).

RESULTS

Xenon consumption was highest during the wash-in phase (9.4 ± 2.1l) and further decreased throughout maintenance of anaesthesia. Comparison of different xenon delivery modes revealed significant reduced xenon consumption during ECO mode (18.5 ± 3.7L (ECO) vs. 24.7 ± 11.5L (AUTO) vs. 29.6 ± 14.3L (MANUAL); p = 0.033). No differences could be detected with regard to anaesthetic depth, oxygenation or performance of anaesthesia.

CONCLUSION

The closed-circuit respirator Felix Dual offers effective reduction of xenon consumption during general surgery when ECO mode is used.

Functional Recovery after Scutellarin Treatment in Transient Cerebral Ischemic Rats: A Pilot Study with (18) F-Fluorodeoxyglucose MicroPET

Objective. To investigate neuroprotective effects of scutellarin (Scu) in a rat model of cerebral ischemia with use of ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) micro positron emission tomography (microPET). Method. Middle cerebral artery occlusion was used to establish cerebral ischemia. Rats were divided into 5 groups: sham operation, cerebral ischemia-reperfusion untreated (CIRU) group, Scu-25 group (Scu 25 mg/kg/d), Scu-50 group (Scu 50 mg/kg/d), and nimodipine (10 mg/Kg/d). The treatment groups were given for 2 weeks. The therapeutic effects in terms of cerebral infarct volume, neurological deficit scores, and cerebral glucose metabolism were evaluated. Levels of vascular density factor (vWF), glial marker (GFAP), and mature neuronal marker (NeuN) were assessed by immunohistochemistry. Results. The neurological deficit scores were significantly decreased in the Scu-50 group compared to the CIRU group (P < 0.001). ¹⁸F-FDG accumulation in the ipsilateral cerebral infarction increased steadily over time in Scu-50 group compared with CIRU group (P < 0.01) and Scu-25 group (P < 0.01). Immunohistochemical analysis demonstrated Scu-50 enhanced neuronal maturation. Conclusion. ¹⁸F-FDG microPET imaging demonstrated metabolic recovery after Scu-50 treatment in the rat model of cerebral ischemia. The neuroprotective effects of Scu on cerebral ischemic injury might be associated with increased regional glucose activity and neuronal maturation.

Regional cerebral blood flow and glucose metabolism during propofol anaesthesia in healthy subjects studied with positron emission tomography

BACKGROUND

General anaesthetics can alter the relationship between regional cerebral glucose metabolism rate (rGMR) and regional cerebral blood flow (rCBF). With the present study, we wanted to assess quantitatively the effects of propofol on rCBF and rGMR in the same healthy volunteers measured with positron emission tomography (PET).

METHODS

(15)O-labelled water and (18)F fluorodeoxyglucose were used as PET tracers to determine rCBF and rGMR, respectively, in eight healthy volunteers during the waking state (baseline) and during propofol anaesthesia. Propofol was titrated to keep a constant hypnotic depth (Bispectral Indes 35-40) throughout the anaesthesia. Changes in rGMR and rCBF were quantified using region-of-interest and voxel-based analyses.

RESULTS

The measured mean propofol concentration was 4.1 ± 0.8 μg/ml during anaesthesia. Compared with the conscious state, total CBF and GMR decreased during the anaesthetic state with 47% and 54%, respectively. In the white and grey matter, rCBF and rGMR were reduced by 37% and 49%, and by 45% and 57%, respectively. Propofol decreased rCBF in all brain structures by 46-55% (P ≤ 0.01) with highest significant decreases in the thalamus and parietal lobe. Regional GMR was reduced in all brain areas to 48-66% (P ≤ 0.01) with highest significant reductions in the occipital lobe, the lingual gyrus, parietal lobe, temporal lobe and thalamus. No increases in rCBF or rGMR happened anywhere.

CONCLUSIONS

General anaesthesia with propofol is associated with a global metabolic and vascular depression in the human brain, with significant shifts in regional blood flow and metabolism indicating marked metabolic and vascular responsiveness in some cortical areas and thalamus.

aepEX monitor for the measurement of hypnotic depth in patients undergoing balanced xenon anaesthesia

BACKGROUND

Previously, we showed a significant difference in the measurements of hypnotic depth by the bispectral index (BIS) and auditory-evoked potentials (AEPs) using the A-line autoregressive index during xenon anaesthesia. In the present study, we evaluate the alternative AEP-based auditory-evoked potential index (aepEX) for the measurement of hypnotic depth in patients undergoing general anaesthesia with xenon.

METHODS

Forty-two patients undergoing elective abdominal surgery were enrolled in this controlled, double-blinded, randomized, clinical study. Patients were randomized to receive either xenon (n=21) or sevoflurane anaesthesia (n=21). During anaesthesia, BIS values were recorded simultaneously with the aepEX monitoring. The anaesthetist performing the anaesthesia was blinded to the hypnotic depth monitors. After surgery, the incidence of recalls and awareness was evaluated.

RESULTS

Patients' characteristics such as gender, age, and weight did not differ between the groups. The aepEX and BIS values behaved similarly during anaesthesia. The comparison of aepEX values during xenon and sevoflurane anaesthesia revealed significantly lower aepEX values in the xenon group after 25 min [xenon: 32.9 (4.8) vs sevoflurane: 39.3 (9.0); P=0.008] and after 35 min [xenon: 31.4 (6.6) vs sevoflurane: 37.0 (6.8); P=0.012]. During anaesthesia, aepEX values correlated with the clinical evaluation of depth of anaesthesia (e.g. >20% changes of the baseline arterial pressure or heart rate, spontaneous breathing and/or intolerance of mechanical ventilation, coughing, abdominal pressing, sweating, eye tearing).

CONCLUSIONS

We found the aepEX monitor to provide index in the range of adequate depth of xenon anaesthesia, when combined with remifentanil infusion in intubated patients undergoing elective abdominal surgery.

[Current developments in xenon research. Importance for anesthesia and intensive care medicine]

The noble gas xenon exerts favorable anesthetic properties along with remarkable hemodynamic stability in healthy patients undergoing elective surgery. It represents the nearly ideal anesthetic and provides safe and well controllable anesthesia although the exact mechanism by which xenon produces anesthesia remains to be elucidated. In addition xenon offers organ protective properties for vital organs including the brain, heart and kidneys which seem to be synergistic when used in combination with therapeutic hypothermia. As the high cost of xenon will probably preclude its wider use as a routine anesthetic, data from extensive tests in large numbers of high risk patients is needed to confirm its possible superiority in this setting.

[Benefits and indications of xenon anaesthesia]

OBJECTIVE

To analyze the current knowledge related to xenon anaesthesia.

DATA SOURCES

References were obtained from computerized bibliographic research (Medline), recent review articles, the library of the service and personal files.

STUDY SELECTION

All categories of articles on this topic have been selected.

DATA EXTRACTION

Articles have been analyzed for biophysics, pharmacology, toxicity and environmental effects, clinical effects and using prospect.

DATA SYNTHESIS

The noble gas xenon has anaesthetic properties that have been recognized 50 years ago. Xenon is receiving renewed interest because it has many characteristics of an ideal anaesthetic. In addition to its lack of effects on cardiovascular system, xenon has a low solubility enabling faster induction of and emergence from anaesthesia than with other inhalational agents. Nevertheless, at present, the cost and rarity of xenon limits widespread use in clinical practice. The development of closed rebreathing system that allowed recycling of xenon and therefore reducing its waste has led to a recent interest in this gas.

CONCLUSION

Reducing its cost will help xenon to find its place among anaesthetic agents and extend its use to severe patients with specific pathologies.

Cuprizone treatment induces demyelination and astrocytosis in the mouse hippocampus

Memory impairment is outstanding within the spectrum of cognitive deficits in multiple sclerosis (MS) patients. Demyelination has been reported in the hippocampus formation of MS patients. The degree of hippocampus lesions in MS strongly correlates with progression of cognitive dysfunction. Because no appropriate animal model for the study of hippocampus demyelination has been established, we used the cuprizone mouse model to investigated demyelination in young adult and aged mice. The myelin status was analyzed by classical histological staining, immunocytochemistry for proteolipoprotein, and electron microscopy. Oligodendrocyte, astroglial, and microglia markers were studied. Cuprizone intoxication induced an almost complete demyelination of distinct hippocampus subregions to a similar extent in young adult and aged male mice. Demyelination was pronounced in a subset of white and gray matter areas, i.e., the stratum lacunosum moleculare containing the perforant path, medial alveus, stratum pyramidale in the cornu ammonis 2/3 region, and hilus region. Besides demyelination, affected areas displayed hypertrophic and hyperplastic astrocytosis. No significant effect on microglia invasion was detected at any investigated time point (0, 3, 5, and 7 weeks). We conclude that cuprizone-induced demyelination provides an adequate animal model to investigate appropriate therapy strategies for the prevention of hippocampus demyelination.