Sevoflurane anesthesia improves cognitive performance in mice, but does not influence in vitro long-term potentation in hippocampus CA1 stratum radiatum

Middle aged CAMKII-Cre:Cbsfl/fl mice: a new model for studying perioperative neurocognitive disorders

Postoperative complications, such as perioperative neurocognitive disorders (PND), have become a major issue affecting surgical outcomes. However, the mechanism of PND remains unclear, and stable animal models of middle-aged PND are lacking. S-adenosylmethionine (SAM), a cystathionine beta-synthase (CBS) allosteric activator, can reduce the level of plasma homocysteine and prevent the occurrence of PND. However, the time and resource-intensive process of constructing models of PND in elderly animals have limited progress in PND research and innovative therapy development. The present study aimed to construct a stable PND model in middle-aged CAMKII-Cre:Cbsfl/fl mice whose Cbs was specifically knocked out in CAMKII positive neurons. Behavioral tests showed that these middle-aged mice displayed cognitive deficits which were aggravated by exploratory laparotomy under isoflurane anesthesia. Compared with typical PND mice which were 18-month-old, these middle-aged mice showed similar cognitive deficits after undergoing exploratory laparotomy under isoflurane anesthesia. Though there was no significant difference in the number of neurons in either the hippocampus or the cortex, a significant increase in numbers of microglia and astrocytes in the hippocampus was observed. These indicate that middle-aged CAMKII-Cre:Cbsfl/fl mice can be used as a new PND model for mechanistic studies and therapy development for PND.

Reduced excitatory neurotransmission in the hippocampus after inflammation and sevoflurane anaesthesia

Background

Inflammation and general anaesthesia likely contribute to perioperative neurocognitive disorders, possibly by causing a neuronal imbalance of excitation and inhibition. We showed previously that treatment with lipopolysaccharide (LPS) and sevoflurane causes a sustained increase in a tonic inhibitory conductance in the hippocampus; however, whether excitatory neurotransmission is also altered remains unknown. The goal of this study was to examine excitatory synaptic currents in the hippocampus after treatment with LPS and sevoflurane. Synaptic plasticity in the hippocampus, a cellular correlate of learning and memory, was also studied.

Methods

Mice were injected with vehicle or LPS (1 mg kg-1 i.p.), and after 24 h they were then exposed to vehicle or sevoflurane (2.3%; 2 h). Hippocampal slices were prepared 48 h later. Excitatory synaptic currents were recorded from pyramidal neurones. Long-term potentiation (LTP) and long-term depression (LTD) were studied in the Schaffer collateral-cornu ammonis 1 pathway.

Results

The amplitude of miniature excitatory postsynaptic currents (EPSCs) was reduced after LPS+sevoflurane (P<0.001), whereas that of spontaneous EPSCs was unaltered, as evidenced by cumulative distribution plots. The frequency, area, and kinetics of both miniature and spontaneous EPSCs were unchanged, as were LTP and LTD.

Conclusions

The reduced amplitude of miniature EPSCs, coupled with the previously reported increase in tonic inhibition, indicates that the combination of LPS and sevoflurane markedly disrupts the balance of excitation and inhibition. Restoring this balance by pharmacologically enhancing excitatory neurotransmission and inhibiting the tonic current may represent an effective therapeutic option for perioperative neurocognitive disorders.

The effect of narcotics on ferroptosis-related molecular mechanisms and signalling pathways

Ferroptosis is a novel programmed cell death form characterized by iron-mediated reactive oxygen species-induced lipid peroxidation and subsequent cell damage that is distinct from apoptosis, necroptosis, pyroptosis, and autophagy. Most studies on ferroptosis are based on its function and mechanism, but there have been relatively few studies on the effects of drugs, especially anaesthetics, on ferroptosis. Therefore, we summarized the recent literature on the effects of anaesthetics on ferroptosis to understand the underlying mechanism. In particular, we focused on the targets of various anaesthetics in different mechanisms of ferroptosis and the effects of ferroptosis induction or inhibition by narcotics on various diseases. The aims of this review are to provide a relatively reasonable drug regimen for clinicians, to explore potential ferroptosis protection drugs and targets, to reduce perioperative complications and to improve the postoperative performance of patients, especially those who are critically ill.

Sevoflurane Exposure in the Developing Brain Induces Hyperactivity, Anxiety-Free, and Enhancement of Memory Consolidation in Mice

Background

Sevoflurane exposure at brain developmental stages has been reported to induce neurotoxicity and, subsequently, results in learning deficits at the juvenile age. In this study, we aimed to investigate the effects of prior early-age sevoflurane exposure on locomotor activity, anxiety, CA1-dependent learning, and spatial memory, as well as synapse changes in mice.

Methods

Totally, 3% sevoflurane was given to neonatal mice at postnatal day 7 for 4 h. These sevoflurane-treated mice were later subjected to open field and Morris water maze tests at their adult age (postnatal days 60–90) to assess their motor activity and spatial learning ability, respectively. The brain slices of sevoflurane-treated and control mice were examined for dendritic spine density and long-term potentiation (LTP) features following behavior tests (postnatal day 60). Protein levels of N-methyl-D-aspartate (NMDA) receptor subtypes and PSD95 in brain lysate were measured by using immunoblotting at the same age (postnatal day 60).

Results

Prior early-age sevoflurane exposure increased the overall moving distance, prolonged the central-area lingering time, and increased the central-area entries of adult mice. Sevoflurane-treated mice spent more time in the target quadrant during the probe test. An increase of the spine density of pyramidal neurons in the CA1 region was observed in sevoflurane-treated mice. NMDA receptor GluN2A subunit, but not the GluN2B or PSD95, was increased in the brain lysate of sevoflurane-treated mice compared with that of control mice. LTP in the hippocampus did not significantly differ between sevoflurane-treated and control mice.

Conclusion

Exposure to sevoflurane for mice during an early brain developmental stage (P7) induces later-on hyperactivity, anxiety-free, and enhancement of memory retention. These observations shed light on future investigations on the underlying mechanisms of sevoflurane’s effect on neuronal development.

Cerebral Glutamate Regulation and Receptor Changes in Perioperative Neuroinflammation and Cognitive Dysfunction

Glutamate is the major excitatory neurotransmitter in the central nervous system and is intricately linked to learning and memory. Its activity depends on the expression of AMPA and NMDA receptors and excitatory amino transporters on neurons and glial cells. Glutamate transporters prevent the excess accumulation of glutamate in synapses, which can lead to aberrant synaptic signaling, excitotoxicity, or cell death. Neuroinflammation can occur acutely after surgical trauma and contributes to the development of perioperative neurocognitive disorders, which are characterized by impairment in multiple cognitive domains. In this review, we aim to examine how glutamate handling and glutamatergic function are affected by neuroinflammation and their contribution to cognitive impairment. We will first summarize the current data regarding glutamate in neurotransmission, its receptors, and their regulation and trafficking. We will then examine the impact of inflammation on glutamate handling and neurotransmission, focusing on changes in glial cells and the effect of cytokines. Finally, we will discuss these changes in the context of perioperative neuroinflammation and the implications they have for perioperative neurocognitive disorders.

Minimal effects from a single exposure to sevoflurane in adult male and female Sprague-Dawley rats

Many people undergo procedures requiring general anesthesia each day and adverse cognitive effects have been reported in response to that anesthesia. Postoperative Cognitive Dysfunction (POCD) may occur in as many as 80% of adults during the first post-surgical week and can have lasting effects. Here, the cognitive and motor effects of sevoflurane exposure in Sprague-Dawley rats was examined along with body weights, blood oxygen saturation, heart rate, and body temperature. Male and female rats were exposed to 2.5% sevoflurane or medical grade air for one hour at postnatal day 115. Beginning the following day, rats began a series of behavioral tests examining locomotor activity, motor coordination, novel object recognition, and spatial learning and memory in a water maze. Blood oxygen saturation, heart rate, and body temperature were not affected by the sevoflurane exposure. A slight effect on locomotor activity was detected, but no effects on motor coordination, novel object recognition, or spatial learning and memory were observed. Brain weights following behavioral testing did not differ. The results reported here along with existing literature suggest sevoflurane is largely without effects on later cognition in adult rodents when exposure is of a relatively short duration and at a relatively low concentration.

DNA Methylation Manipulation of Memory Genes Is Involved in Sevoflurane Induced Cognitive Impairments in Aged Rats

DNA methylation is an essential epigenetic mechanism involving in gene transcription modulation. An age-related increase in promoter methylation has been observed for neuronal activity and memory genes, and participates in neurological disorders. However, the position and precise mechanism of DNA methylation for memory gene modulation in anesthesia related cognitive impairment remained to be determined. Here, we studied the effects of sevoflurane anesthesia on the transcription of memory genes in the aged rat hippocampus. Then, we investigated changes in DNA methylation of involved genes and verified whether dysregulated DNA methylation would contribute to anesthesia induced cognitive impairment. The results indicated that sevoflurane anesthesia down-regulated the mRNA and protein levels of three memory genes, Arc, Bdnf, and Reln, which were accompanied with promoter hypermethylation and increased Dnmt1, Dnmt3a, and Mecp2 expression, and finally impaired hippocampus dependent memory. Furthermore, inhibition of DNA hypermethylation by 5-Aza rescued sevoflurane induced memory gene expression decrease and cognitive impairment. These findings provide an epigenetic understanding for the pathophysiology of cognitive impairment induced by general anesthesia in aged brain.

Nonexperimental Xenobiotics: Unintended Consequences of Intentionally Administered Substances in Terrestrial Animal Models

Review of the use of nonexperimental xenobiotics in terrestrial animal models and the potential unintended consequences of these compounds, including drug-related side effects and adverse reactions.

Iron overload contributes to general anaesthesia-induced neurotoxicity and cognitive deficits

Background

Increasing evidence suggests that multiple or long-time exposure to general anaesthesia (GA) could be detrimental to cognitive development in young subjects and might also contribute to accelerated neurodegeneration in the elderly. Iron is essential for normal neuronal function, and excess iron in the brain is implicated in several neurodegenerative diseases. However, the role of iron in GA-induced neurotoxicity and cognitive deficits remains elusive.

Methods

We used the primary hippocampal neurons and rodents including young rats and aged mice to examine whether GA impacted iron metabolism and whether the impact contributed to neuronal outcomes. In addition, a pharmacological suppression of iron metabolism was performed to explore the molecular mechanism underlying GA-mediated iron overload in the brain.

Results

Our results demonstrated that GA, induced by intravenous ketamine or inhalational sevoflurane, disturbed iron homeostasis and caused iron overload in both in vitro hippocampal neuron culture and in vivo hippocampus. Interestingly, ketamine- or sevoflurane-induced cognitive deficits, very likely, resulted from a novel iron-dependent regulated cell death, ferroptosis. Notably, iron chelator deferiprone attenuated the GA-induced mitochondrial dysfunction, ferroptosis, and further cognitive deficits. Moreover, we found that GA-induced iron overload was activated by NMDAR-RASD1 signalling via DMT1 action in the brain.

Conclusion

We conclude that disturbed iron metabolism may be involved in the pathogenesis of GA-induced neurotoxicity and cognitive deficits. Our study provides new vision for consideration in GA-associated neurological disorders.

A systematic review: comparative analysis of the effects of propofol and sevoflurane on postoperative cognitive function in elderly patients with lung cancer

Background

The potential risk for cognitive impairment following surgery and anesthesia is a common concern, especially in the elderly and more fragile patients. The risk for various neurocognitive effects is thus an area of importance. The independent impact of surgery and anesthesia is still not known. Likewise, the independent effect of different drugs used during anesthesia is a matter of debate, as is the number and amounts of drugs used and the “depth of anesthesia.” So, understanding the drug-related phenomenon and mechanisms for postoperative cognitive impairment is essential. This meta-analysis aims to compare the effects of propofol and sevoflurane anesthesia on postoperative cognitive function in elderly patients with lung cancer.

Methods

This study is a systematic review and meta-analysis for controlled clinical studies. Public-available online databases were searched to identify eligible randomized placebo-controlled trials or prospective cohort studies concerning the effects of propofol and sevoflurane on postoperative cognitive function. The primary endpoints are postoperative mini-mental state examination (MMSE) scores at various time points; the secondary endpoint is the serum S100beta concentration 24 h after surgery. Standard mean differences (SMDs) along with 95% confidence intervals (CIs) were extracted and analyzed using random or fixed-effects models. Analyses regarding heterogeneity, risk of bias assessment, and sensitivity were performed.

Results

We searched 1626 eligible publications and 14 studies of 1404 patients were included in the final analysis. The majority of included studies had been undertaken in Asian populations. Results suggested that propofol has a greater adverse effect on cognitive function in the elderly patients with lung cancer than sevoflurane. There were significant differences in issues of MMSE 6 h (11 studies; SMD -1.391, 95% CI -2.024, − 0.757; p < 0.001), MMSE 24 h (14 studies; SMD -1.106, 95% CI -1.588, − 0.624; p < 0.001), MMSE 3d (11 studies; SMD -1.065, 95% CI -1.564, − 0.566; p < 0.001), MMSE 7d (10 studies; SMD -0.422, 95% CI -0.549, − 0.295; p < 0.001), and serum S100beta concentration at 1 day after surgery (13 studies; SMD 0.746, 95% CI 0.475, 1.017; p < 0.001).

Conclusion

Propofol has a more significant adverse effect on postoperative cognitive function in elderly patients with lung cancer than sevoflurane.

Sevoflurane Impairs Short-Term Memory by Affecting PSD-95 and AMPA Receptor in the Hippocampus of a Mouse Model

Objective

To explore the effects of sevoflurane on the latency and error times of the passive avoidance and levels of PSD-95 and AMPA receptors in the hippocampus. We evaluated the effects of sevoflurane on short-term memory in adult mice and explored the possible mechanism.

Methods

144 Kunming mice (2-3 months, 30-35 g) were randomly divided into two groups A (n = 64) and B (n = 80) and received the dark-avoidance (DA) and step-down avoidance (SA) tests, respectively. The groups DA and SA were further divided into control (inhaled 40% O₂ 2 h) and sevoflurane (3.3% sevoflurane and 40% O₂ 2 h) subgroups. Before inhalation intervention, all mice were trained to be familiar with the Morris water maze (MWM). According to the test points of behavioral indicators, 8 mice were randomly selected from each subgroup at point 12 h (T1), 24 h (T2), 48 h (T3), and 72 h (T4) after inhalation intervention. The step-through latency and error times were measured in 5 min. After the behavioral test, the mice were killed and the tissues of the hippocampus were taken for hematoxylin and eosin (H&E) staining. The expression level of PSD-95 and AMPA receptors in the hippocampus was detected by immunohistochemistry and Western Blot. The changes of synaptic transmission were measured via electrophysiology analysis of hippocampal slices.

Results

The mice in the control subgroups found the platform in a shorter pathway than those in the sevoflurane subgroups during an MWM test. The step-through latency of T1 and T2 in the sevoflurane subgroup was shorter than baseline time, and the error times were increased in 5 min and higher than baseline time when compared with the control subgroup (P < 0.05) in the A and B groups. Compared with the control subgroup, the expression level of PSD-95 and AMPA receptors in the hippocampus was decreased at T1 and T2 in the sevoflurane subgroup (P < 0.05). The nerve cells were partially swelling. Electrophysiology analysis showed that the levels of PSD-95 and AMPA receptor expression were associated with synaptic transmission.

Conclusion

Sevoflurane impaired short-term memory in adult mice by inhibiting the expression of PSD-95 and AMPA receptors in the hippocampus, which led to the decrease in synaptic transmission.

Cognitive decline in Tg2576 mice shows sex-specific differences and correlates with cerebral amyloid-beta

Patients suffering from Alzheimer's disease show a sex-dependent decline of cognitive function. The aim of this investigation was to show these differences in an animal model for Alzheimer's disease and to determine whether this effect is correlated to amyloid-beta-induced pathophysiological changes. Therefore, we assessed cognitive performance with the modified hole-board test in female and male Tg2576 and wild type mice at the age of 6, 8, 10, 12, 14, and 16 months and correlated these findings to the total amount of soluble amyloid-beta and insoluble amyloid deposits in the brain. Tg2576 mice perform worse than wild types. Female Tg2576 mice develop an accentuated cognitive impairment (wrong choice total) beginning at the age of 12 months compared to their male littermates. Alterations in the mice's behaviour do not show interference with these deficits. Cognitive impairment is correlated to the amount of soluble amyloid-beta and insoluble amyloid deposits in the brain in a sex-dependent manner.

Collapsin Response Mediator Protein-2 Ameliorates Sevoflurane-Mediated Neurocyte Injury by Targeting PI3K-mTOR-S6K Pathway

Background

Collapsin response mediator protein-2 (CRMP-2) is the first member of the CRMP family that has been identified in primary neuronal cells; it was originally found and identified in the regulation of microtubule dimerization into microtubules.

Material/Methods

In the present study, we aimed to investigate the roles and mechanisms of CRMP-2 in sevoflurane-induced neurocyte injury. Cell viability, proliferation, and apoptosis were measured by Cell Counting Kit-8 (CCK-8) assay and flow cytometry. Colorimetry was performed to measure the activity of caspase-3. Western blot and quantitative real-time reverse transcription assays were used to evaluate the related mRNAs and proteins expression.

Results

We found that CRMP-2 reversed the inhibitory effect of sevoflurane on the viability of nerve cells. Moreover, CRMP-2 accelerated the proliferation and suppressed the apoptosis of sevoflurane-induced nerve cells. CRMP-2 modulated the expression levels of apoptosis-associated protein in sevoflurane-induced nerve cells. Furthermore, it was demonstrated that CRMP-2 impacted the PI3K-mTOR-S6K pathway.

Conclusions

CRMP2 ameliorated sevoflurane-mediated neurocyte injury by targeting the PI3K-mTOR-S6K pathway. Thus, CRMP2 might be an effective target for sevoflurane-induced neurocyte injury therapies.

A daily single dose of a novel modafinil analogue CE-123 improves memory acquisition and memory retrieval

Dopamine reuptake inhibitors have been shown to improve cognitive parameters in various tasks and animal models. We recently reported a series of modafinil analogues, of which the most promising, 5-((benzhydrylsulfinyl)methyl) thiazole (CE-123), was selected for further development. The present study aims to characterize pharmacological properties of CE-123 and to investigate the potential to enhance memory performance in a rat model. In vitro transporter assays were performed in cells expressing human transporters. CE-123 blocked uptake of [3H] dopamine (IC50 = 4.606 μM) while effects on serotonin (SERT) and the norepinephrine transporter (NET) were negligible. Blood-brain barrier and pharmacokinetic studies showed that the compound reached the brain and lower elimination than R-modafinil. The Pro-cognitive effect was evaluated in a spatial hole-board task in male Sprague-Dawley rats and CE-123 enhances memory acquisition and memory retrieval, represented by significantly increased reference memory indices and shortened latency. Since DAT blockers can be considered as indirect dopamine receptor agonists, western blotting was used to quantify protein levels of dopamine receptors D1R, D2R and D5R and DAT in the synaptosomal fraction of hippocampal subregions CA1, CA3 and dentate gyrus (DG). CE-123 administration in rats increased total DAT levels and D1R protein levels were significantly increased in CA1 and CA3 in treated/trained groups. The increase of D5R was observed in DG only. Dopamine receptors, particularly D1R, seem to play a role in mediating CE-123-induced memory enhancement. Dopamine reuptake inhibition by CE-123 may represent a novel and improved stimulant therapeutic for impairments of cognitive functions.

Role of the hippocampal 5-HT1A receptor-mediated cAMP/PKA signalling pathway in sevoflurane-induced cognitivedysfunction in aged rats

Objective

This study aimed to evaluate the role of the hippocampal 5-hydroxytryptamine-1A (5-HT1A)-mediated cyclic adenosine monophosphate/protein kinase A (cAMP/PKA) signalling pathway in sevoflurane-induced cognitive dysfunction in aged rats.

Methods

Sixty 18-month-old Sprague–Dawley rats were divided into the control (n = 30) and experimental (Sev, n = 30) groups. The experimental group inhaled 50% air/oxygen mixture (2 L/min) and 2% sevoflurane for 4 hours. The control group inhaled 50% air/oxygen mixture (2 L/min) for 4 hours. The Morris water maze test was performed The mRNA expression of 5-HT1A receptor, and cAMP PKA, cAMP response element-binding protein (CREB), and phosphorylated CREB (p-CREB) protein expression were determined.

Results

The escape latency and swimming distance were greater, and the number of crossings of the platform location and time spent in the platform quadrant were less in the Sev group compared with the control group. cAMP, PKA, CREB, and p-CREB protein expression was downregulated in the Sev group 1 day after anaesthesia compared with the control group. Hippocampal 5-HT1A receptor mRNA expression was higher 7 days after anaesthesia compared with the control group.

Conclusion

Sevoflurane-induced cognitive dysfunction in aged rats may be related to inhibited expression of the hippocampal 5-HT1A receptor-mediated cAMP/PKA signalling pathway.

Nampt/RelB pathway protects learning and memory ability in aged rats after general anesthesia with sevoflurane and nitrous oxide

Anesthesia-induced postoperative cognitive dysfunction (POCD) has been confirmed in elderly patients, while studies have shown that Nampt protein is critical for learning and memory. To better understand the mechanism of anesthesia-induced POCD, we studied the behavioral and biochemical changes in aged rats that were exposed to sevoflurane (Sev) and nitrous oxide (N2O) for 4 hours. Rats were randomly divided into control group and anesthesia group. The anesthesia group rats were given 1.3% Sev and 50% N2O for 4 hours, and controls with 50% O2 for same time. Morris Water Maze test was used to test the rat's ability to learn and remember 24 hours exposure. The result shown that Sev-N2O anesthesia induced a significant deficit in short-term spatial learning acquisition and memory retention, but it had no significant deficit in long-term. After 48 hours Sev-N2O anesthesia, the neuronal apoptosis and the expression of Bax, PARP-1 in hippocampus of rats increased significantly, and the expression of Nampt, RelB decreased significantly. However, Nampt activators could reduce the apoptosis of hippocampal primary cells in vitro after 4 hours exposed with Sev-N2O. Thus, we believed that down-regulation of Nampt/RelB signaling was closely related to neuronal apoptosis in the hippocampus contributed to the neurotoxicity and cognitive dysfunction induced by general anesthesia with sevoflurane-nitrous oxide.

Sevoflurane Affects Oxidative Stress and Alters Apoptosis Status in Children and Cultured Neural Stem Cells

Anesthesia-induced neurotoxicity in immature animals has raised concerns about similar effects occurring in young children. Our study investigated two commonly used anesthetics-sevoflurane and propofol-for neurotoxicity in young children. Forty-seven children (aged 12-36 months) undergoing hypospadias repair surgery were randomized to receive sevoflurane (SG, n = 24) or propofol (PG, n = 23) general anesthesia. Venous blood was collected at three different times-immediately after induction, 2 h, and 3 days after surgery. The cellular portion was assessed for antioxidant defense and DNA damage, using enzyme assay kits and qRT-PCR, respectively, while serum was used to treat cultured neural stem cells (NSCs). MTT assay and TUNEL staining were performed, and the mRNA levels of antioxidant enzymes and apoptosis indicators were evaluated by qRT-PCR. Antioxidant defense and apoptosis status in the SG group were significantly higher than in the PG group at 2 h after surgery. Additionally, exposure of NSCs to postoperative serum of the SG group resulted in decreased cell density and viability, increased TUNEL-positive cells, elevated mRNA levels of antioxidant enzymes, and cleaved caspase-3 expression. Our data shows for the first time that in young children, administration of sevoflurane, but not propofol, leads to temporally increased antioxidant defense and apoptosis status as well as damage of NSCs.

Short-Term and Long-Term Effects of Dexamethasone on Cognitive Dysfunction Induced by Sevoflurane in Adult Rats

OBJECTIVE

Postoperative cognitive dysfunction (POCD) is common after anaesthesia in elderly patients. However, it may appear in patients of all ages. The main pathogenesis of cognitive dysfunction remains unclear, although there is some evidence that brain inflammation may alter cognitive abilities. In the present study, we aim to evaluate short-term and long-term effects of dexamethasone on cognitive dysfunction induced by sevoflurane anaesthesia in adult rats.

METHODS

Seven-month-old 30 male Wistar albino rats were randomised into three groups: sevoflurane group (exposure to sevoflurane), sevoflurane + dexamethasone group (exposure to sevoflurane and dexamethasone injection), and control group (exposure to 100% oxygen). Spatial learning and short-term (7 days after exposure) and long-term (30 days after exposure) memory were evaluated using Morris water maze test.

RESULTS

Sevoflurane induced significant deficit in spatial learning and short-term and long-term memory in adult rats. Dexamethasone-treated animals exposed to sevoflurane had equivalent performance as control animals in training and probe trials.

CONCLUSION

Sevoflurane may impair spatial learning and short-term and long-term memories in adult rats. The co-administration of dexamethasone and sevoflurane may ameliorate short-term and long-term cognitive dysfunctions induced by sevoflurane in adult rats.

Voluntary exercise rescues sevoflurane-induced memory impairment in aged male mice

Postoperative cognitive impairment is especially common in older patients following major surgery. Although exposure to sevoflurane is known to cause memory deficits, few studies have examined the putative approaches to reduce such impairments. This study tested the hypotheses that sevoflurane exposure can decrease NR2B subunit-containing NMDA receptor activity in hippocampus of aged mice, and voluntary exercise may counteract the declining hippocampal functions. We found that long exposure (3 h/day for 3 days), but not short exposure (1 h/day for 3 days), to 3 % sevoflurane produced a long-lasting spatial memory deficits up to 3 weeks in aged mice, and such an effect was not due to the neuronal loss in the hippocampus, but was correlated with a long-term decrease in Fyn kinase expression and NR2B subunit phosphorylation in the hippocampus. Furthermore, voluntary exercise rescued sevoflurane-induced spatial memory deficits in aged mice and restored Fyn kinase expression and NR2B subunit phosphorylation in the hippocampus to a level comparable to control animals. Generally, our results suggested that Fyn-mediated NR2B subunit phosphorylation may play a critical role in sevoflurane-induced impairment in cognitive functions in aged animals, and voluntary exercise might be an important non-pharmacological approach to treatment of inhaled anesthetics-induced postoperative cognitive impairment in clinical settings.

Sevoflurane prevents stroke-induced depressive and anxiety behaviors by promoting cannabinoid receptor subtype I-dependent interaction between β-arrestin 2 and extracellular signal-regulated kinases 1/2 in the rat hippocampus

One of the most frequent psychological consequences of stroke is depression. Previous animal studies have demonstrated that post-conditioning with sevoflurane protects against focal cerebral ischemia and reperfusion injury. Thus, we hypothesized that repeated exposure to sevoflurane after transient ischemia can prevent the development of depressive-like behavior. To test this hypothesis, we induced transient cerebral ischemia via transient occlusion of bilateral common carotid arteries and examined the effects of subsequent repeated exposure to sevoflurane on sucrose preference, locomotor activity, and rearing activity in rats. To explore the putative neurobiological mechanisms, we further investigated the roles of hippocampal CB1 receptor in the behavioral effects of sevoflurane. We found that repeated sevoflurane exposures reversed ischemia-induced depressive-like behaviors. Furthermore, CB1 receptor inhibition in the dorsal hippocampus (DH) abolished the effects of sevoflurane exposures on ischemia-induced depressive-like behaviors. In addition, repeated sevoflurane exposures increased CB1 receptor expression and endocannabinoids levels in the DH of ischemic rats. Moreover, repeated sevoflurane exposures enhanced the expression of β-arrestin 2, increased the activation of extracellular signal-regulated kinases (ERK)1/2, and promoted the interaction of β-arrestin 2 and ERK1/2 in the DH, and such effects were reversed by CB1 receptor antagonism in the DH. Finally, β-arrestin 2 expression and ERK1/2 activation in the DH were critical for the preventative effects of sevoflurane exposures on ischemia-induced depressive-like behaviors. Taken together, our results suggested that sevoflurane exposure after brain ischemia may prevent the development of depression, and such preventative effects of sevoflurane are likely ascribed to the activation of CB1 receptor-mediated β-arrestin 2-ERK1/2 signaling pathways. We propose that the following mechanisms are critical for the preventative effects of sevoflurane against post-stroke depressive and anxiety behaviors: repeated sevoflurane exposure after transient brain ischemia enhances N-arachidonoylethanolamine (AEA) and 2-Arachidonoylglycerol (2-AG) levels and normalize cannabinoid receptor type 1 (CB1) receptor expression in the dorsal hippocampus, which results in enhanced interaction of β-arrestin 2 and extracellular signal-regulated kinases (ERK1/2) and increased ERK1/2 activation, leading to decreased depressive and anxiety behaviors. We think these findings should provide a new strategy for treatment of post-stroke depression.

Effects of Sevoflurane on Young Male Adult C57BL/6 Mice Spatial Cognition

Inhalation anesthetics are reported to affect cognition in both animals and humans. The influence of inhalation anesthetics in learning and memory are contradictory. We therefore investigated the effects of sevoflurane anesthesia with different durations on cognitive performance and the levels of NMDA receptor subunit NR2B, phosphorylated ERK1/2 (p-ERK1/2) and activated caspase3 in mouse hippocampus. We anaesthetized eight-week old male C57BL/6 mice with 2.5% sevoflurane for durations ranging from one to four hours. Non-anaesthetized mice served as controls. Mice exposed to sevoflurane for one to three hours showed improved performance, whereas mice with exposure up to four hours displayed similar behavioral performance as control group. NR2B was increased both at 24h and at two weeks post sevoflurane exposure in all groups. The p-ERK1/2: total ERK1/2 ratio increased at 24h in all anesthesia groups. The ratio remained elevated at two weeks in groups with two- to four-hour exposure. Activated caspase3 was detected elevated at 24h in groups with two- to four-hour exposure. The elevated trend of activated caspase3 was still detectable at two weeks in groups with three- to four-hour exposure. At two weeks post anesthesia, the typical morphology associated with apoptotic cells was observed in the hippocampus of mice exposed to four hours of sevoflurane. Our results indicate that 2.5% sevoflurane exposure for one to three hours improved spatial cognitive performance in young adult mice. The cognitive improvement might be related to the increase of NR2B, the p-ERK1/2: total ERK1/2 ratio in hippocampus. However, exposure to sevoflurane for four hours caused neurotoxicity due to caspase3 activation and apoptosis.

Duration-dependent regulation of autophagy by isoflurane exposure in aged rats

Current evidence suggests a central role for autophagy in many inflammatory brain disorders, including Alzheimer's disease (AD). Furthermore, it is also well accepted that some inhalation anesthetics, such as isoflurane, may cause AD-like neuropathogenesis and resultant postoperative cognitive dysfunction, especially in the elderly population. However, the impact of inhalation anesthetics on autophagic components in the brain remains to be documented. Hence, our objective was to investigate the effects of different durations of isoflurane exposure on hippocampus-dependent learning and hippocampal autophagy in aged rats. Aged Sprague-Dawley rats (20 months old) were randomly exposed to 1.5% isoflurane or 100% oxygen for 1 or 4 h. Animals were then trained in the Morris water maze (4 trials/day for 5 consecutive days). Hippocampal phagophore formation markers, beclin 1 and protein microtubule-associated protein 1 light chain-3B (LC3B), as well as p62, an indicator of autophagic flux, were quantified by western blotting. There was no significant difference in the escape latencies and time spent in the target quadrant, as well as hippocampal expression of beclin 1, LC3B-II, and p62 at 24 h post-anesthesia between the 1-h isoflurane-exposed rats and their controls (P >0.05). Four-hour exposure to isoflurane resulted in spatial learning and memory deficits, as evidenced by prolonged escape latencies on days 4 and 5 post-anesthesia and less time spent in the target quadrant than sham-exposed animals (P <0.05). These events were accompanied by a decline in hippocampal expression of LC3B-I, LC3B-II, and beclin 1 24 h after isoflurane (P <0.01 and P <0.05). Nevertheless, no significant change in p62 expression was found. Further kinetics study of autophagic changes induced by 4 h of isoflurane showed a transient upregulation of LC3B-I, LC3B-II, and beclin 1 at the end of exposure and a subsequent striking decrease within 12-24 h post-anesthesia (P <0.05). Hippocampal p62 peaked at 6 h but subsequently resolved. These results from our pilot in vivo study support a duration-dependent relationship between 1.5% isoflurane exposure, and spatial cognitive function as well as hippocampal phagophore formation.

Hippocampal long-term potentiation in adult mice after recovery from ketamine anesthesia

Ketamine is frequently used to induce analgesia or anesthesia in laboratory animals, but its effects on learning and memory are poorly characterized. Long-term potentiation (LTP) is considered a cellular mechanism for learning and memory. Ketamine administration immediately abolishes hippocampal LTP in vivo, but whether this effect persists is not known. The authors administered one of two doses of ketamine to adult male C57BL/6 mice and measured LTP in hippocampal slices from the mice 24 h later. Neither LTP induction nor LTP maintenance differed significantly in mice that were administered ketamine compared with mice that were administered saline. The findings suggest that a single intraperitoneal dose of ketamine does not persistently alter LTP in adult male mice.