Isoflurane induces cognitive deficits in the Morris water maze task in rats:

Physical activity compensates for isoflurane-induced selective impairment of neuronal progenitor cell proliferation in the young adult hippocampus

General anesthesia is considered a risk factor for postoperative cognitive dysfunction. However, it is unclear what the neuronal and cognitive consequences of general anesthesia are and whether they can be treated. One possible pathomechanism is hippocampal neurogenesis. We investigated how the anesthetic isoflurane affects adult hippocampal neurogenesis and associated cognitive functions and whether the neurogenic stimulus of physical activity reverses isoflurane-induced changes. We exposed young adult mice to isoflurane (ISO) - half had access to a running wheel (ISO-RW). Both groups were compared with a control condition (CTR; CTR-RW). Cell proliferation and survival in the dentate gyrus of the hippocampus were quantified histologically 48 h and 3 weeks after anesthesia by bromodeoxyuridine incorporation. Cell phenotype was determined by expression of neuronal markers, and the extent of continuous endogenous neuronal proliferation was estimated from the number of doublecortin-positive cells. The Morris water maze was used to test hippocampus-dependent functions. We found that isoflurane decreased proliferation of neuronal progenitor cells, whereas survival of mature neurons remained intact. Consistent with intact neuronal survival, spatial memory associated with neurogenesis also proved intact in the Morris water maze despite isoflurane exposure. Physical activity attenuated the observed neuronal changes by preventing the decrease in newborn neuronal progenitor cells and the decline in continuous endogenous neuronal proliferation in isoflurane-treated animals. In conclusion, isoflurane selectively impairs neuronal proliferation but not survival or neurogenesis-linked cognition in adult mice. The observed adverse effects can be attenuated by physical activity, a cost-effective means of preventing the neurogenic consequences of general anesthesia.

Cognitive- and memory-enhancing effects of Augmentin in Alzheimer’s rats through regulation of gene expression and neuronal cell apoptosis

Introduction: Alzheimer’s disease (AD) is the most common type of dementia among older persons. This study looked at how Augmentin affected behavior, gene expression, and apoptosis in rats in which AD had been induced by scopolamine.

Methods: The rats were divided into five groups: control, sham, memantine, Augmentin, and pre-Augmentin (the last group received Augmentin before scopolamine administration and was treated with memantine). A Morris water maze was utilized to measure spatial memory in the animals, and real-time quantitative reverse transcription PCR (qRT-PCR) and flow cytometry were employed to analyze gene expression and neuronal cell apoptosis, respectively.

Results: Memantine and Augmentin increased spatial memory in healthy rats. The use of scopolamine impaired spatial memory. Both Augmentin and memantine improved spatial memory in AD rats, particularly in the group that received memantine; however, the outcomes were more substantial when Augmentin was administered before scopolamine was given to induce AD. Furthermore, the expression of presenilin-2 (PSEN2) and inositol-trisphosphate 3-kinase B (ITPKB) increased, whereas the expression of DEAD-box helicase 5 (DDX5) fell in the AD-treated groups; however, the results were more substantial after combination therapy. According to flow cytometry studies, Augmentin pre-treatment reduced apoptosis in AD rats.

Discussion: The results showed that administering Augmentin to AD rats before memantine improved their spatial memory, reduced neuronal cell death, upregulated protective genes, and suppressed genes involved in AD pathogenesis.

Arsenic exposure via drinking water during pregnancy and lactation induces autism-like behaviors in male offspring mice

Exposure to arsenic (As), an environmental toxicant, causes damages to the central nervous system (CNS) structure and function. Emerging epidemiological studies support that exposure to As, especially during the critical periods of the CNS development, may act as an environmental risk factor of autism spectrum disorders (ASD), which is characterized by behavioral changes, including abnormal social behaviors, restricted interests and repetitive behaviors. However, direct evidence supporting the cause-effect relationship between As exposure and the risk of ASD is still missing. Thus, we aimed to investigate whether As exposure during pregnancy and lactation led to autism-like behaviors in offspring mice in the present study. We established a mice model of exposure to As via drinking water during pregnancy and lactation and conducted a battery of behavioral tests to evaluate social behaviors, repetitive behaviors, anxiety behaviors and learning and memory ability in offspring mice. We found that perinatal exposure to As caused autism-like behaviors in male offspring, which demonstrated by abnormal social behaviors and repetitive behaviors. Anxiety-like behaviors, and learning and memory impairments, known as concomitant behavioral phenotypes in mice with autism-like behaviors, were also observed. Decreases of synaptic density, especially in cortex, hippocampus and cerebellum, are extensively observed in both ASD patients and animal models of ASD. Thus, immunofluorescence staining and western blotting were used to observe the expression of PSD-95 and SYP, well-known markers for presynaptic and postsynaptic membranes, to assess the synaptic density in offspring cortex, hippocampus and cerebellum. We found perinatal exposure to As decreased the expression of PSD-95 and SYP in these brain regions. This indicated that perinatal exposure to As caused decreases of synaptic density, a typical autism-like cellular alteration in brains, which may contribute to autism-like behaviors in offspring.

Anesthesia-Induced Oxidative Stress: Are There Differences between Intravenous and Inhaled Anesthetics?

Agents used for the induction of anesthesia have been shown to either promote or mitigate oxidative stress. A fine balance between the presence of reactive oxygen species (ROS) and antioxidants is crucial for the proper normal functioning of the cell. A basal concentration of ROS is essential for the manifestation of cellular functions, whereas disproportionate levels of ROS cause damage to cellular macromolecules such as DNA, lipids, and proteins, eventually leading to necrosis and apoptosis. Increased ROS has been linked with numerous illnesses, such as cardiovascular, immune system, liver, and kidney, and has been shown to promote cancer and accelerate aging. Knowledge of the various pharmacologic agents that increase or reduce oxidative stress may promote a safer way of inducing anesthesia. Furthermore, surgery itself leads to increased ROS production and ischemia/reperfusion injury. Indeed, increased perioperative oxidative stress has been correlated with increased postoperative complications and prolonged recovery. Anesthesiologists care for patients during the whole spectrum of perioperative care and thus are in a unique position to deliver countermeasures to oxidative stress. Using preferentially an induction agent which reduces oxidative stress might lead to better clinical outcomes and fewer postoperative complications. Propofol has been shown in several studies to reduce oxidative stress, which reduces postoperative complications and leads to a faster recovery, and thus might represent the preferred induction agent in the right clinical setting.

Return of the Righting Reflex Does Not Portend Recovery of Cognitive Function in Anesthetized Rats

As the number of individuals undergoing general anesthesia rises globally, it becomes increasingly important to understand how consciousness and cognition are restored after anesthesia. In rodents, levels of consciousness are traditionally captured by physiological responses such as the return of righting reflex (RORR). However, tracking the recovery of cognitive function is comparatively difficult. Here we use an operant conditioning task, the 5-choice serial reaction time task (5-CSRTT), to measure sustained attention, working memory, and inhibitory control in male and female rats as they recover from the effects of several different clinical anesthetics. In the 5-CSRTT, rats learn to attend to a five-windowed touchscreen for the presentation of a stimulus. Rats are rewarded with food pellets for selecting the correct window within the time limit. During each session we tracked both the proportion of correct (accuracy) and missed (omissions) responses over time. Cognitive recovery trajectories were assessed after isoflurane (2% for 1 h), sevoflurane (3% for 20 min), propofol (10 mg/kg I.V. bolus), ketamine (50 mg/kg I.V. infusion over 10 min), and dexmedetomidine (20 and 35 μg/kg I.V. infusions over 10 min) for up to 3 h following RORR. Rats were classified as having recovered accuracy performance when four of their last five responses were correct, and as having recovered low omission performance when they missed one or fewer of their last five trials. Following isoflurane, sevoflurane, and propofol anesthesia, the majority (63-88%) of rats recovered both accuracy and low omission performance within an hour of RORR. Following ketamine, accuracy performance recovers within 2 h in most (63%) rats, but low omission performance recovers in only a minority (32%) of rats within 3 h. Finally, following either high or low doses of dexmedetomidine, few rats (25-32%) recover accuracy performance, and even fewer (0-13%) recover low omission performance within 3 h. Regardless of the anesthetic, RORR latency is not correlated with 5-CSRTT performance, which suggests that recovery of neurocognitive function cannot be inferred from changes in levels of consciousness. These results demonstrate how operant conditioning tasks can be used to assess real-time recovery of neurocognitive function following different anesthetic regimens.

The genus Glycyrrhiza (Fabaceae family) and its active constituents as protective agents against natural or chemical toxicities

Licorice is the dried roots and rhizomes of various species of the genus Glycyrrhiza (Fabaceae) that have been used in folk medicine from ancient times. Many important research projects have established several beneficial effects for this medicinal herb, including antiinflammatory, antimicrobial, antiviral, antiprotozoal, antioxidant, antihyperglycemic, antihyperlipidemic, hepatoprotective, and neuroprotective. Licorice contains important bioactive components, such as glycyrrhizin (glycyrrhizic, glycyrrhizinic acid), liquiritigenin, liquiritin, and glycyrrhetinic acid. The protective effects of licorice and its main chemical components against toxins and toxicants in several organs including the brain, heart, liver, kidney, and lung have been shown. In this comprehensive review article, the protective effects of these constituents against natural, industrial, environmental, and chemical toxicities with attention on the cellular and molecular mechanism are introduced. Also, it has been revealed that this plant and its main compounds can inhibit the toxicity of different toxins by the antioxidant, antiinflammatory, and anti-apoptotic properties as well as the modulation of Inhibitor of kappaB kinase (IKK), Extracellular signal-regulated protein kinase1/2 (ERK1/2), p38, inducible nitric oxide synthase, and nuclear factor-κB (NF-κB) signaling pathways. More high-quality investigations in both experimental and clinical studies need to firmly establish the efficacy of licorice and its main constituents against toxic agents.

Effects of general anesthetics on synaptic transmission and plasticity

General anesthetics depress excitatory and/or enhance inhibitory synaptic transmission principally by modulating the function of glutamatergic or GABAergic synapses, respectively, with relative anesthetic agent-specific mechanisms. Synaptic signaling proteins, including ligand- and voltage-gated ion channels, are targeted by general anesthetics to modulate various synaptic mechanisms, including presynaptic neurotransmitter release, postsynaptic receptor signaling, and dendritic spine dynamics to produce their characteristic acute neurophysiological effects. As synaptic structure and plasticity mediate higher-order functions such as learning and memory, long-term synaptic dysfunction following anesthesia may lead to undesirable neurocognitive consequences depending on the specific anesthetic agent and the vulnerability of the population. Here we review the cellular and molecular mechanisms of transient and persistent general anesthetic alterations of synaptic transmission and plasticity.

Recovery of consciousness and cognition after general anesthesia in humans

Understanding how the brain recovers from unconsciousness can inform neurobiological theories of consciousness and guide clinical investigation. To address this question, we conducted a multicenter study of 60 healthy humans, half of whom received general anesthesia for 3 hr and half of whom served as awake controls. We administered a battery of neurocognitive tests and recorded electroencephalography to assess cortical dynamics. We hypothesized that recovery of consciousness and cognition is an extended process, with differential recovery of cognitive functions that would commence with return of responsiveness and end with return of executive function, mediated by prefrontal cortex. We found that, just prior to the recovery of consciousness, frontal-parietal dynamics returned to baseline. Consistent with our hypothesis, cognitive reconstitution after anesthesia evolved over time. Contrary to our hypothesis, executive function returned first. Early engagement of prefrontal cortex in recovery of consciousness and cognition is consistent with global neuronal workspace theory.

Dissociable effects of dietary sodium in early life upon somatic growth, fluid homeostasis, and spatial memory in mice of both sexes

Postnatal growth failure is a common morbidity for preterm infants and is associated with adverse neurodevelopmental outcomes. Although sodium (Na) deficiency early in life impairs somatic growth, its impact on neurocognitive functions has not been extensively studied. We hypothesized that Na deficiency during early life is sufficient to cause growth failure and program neurobehavioral impairments in later life. C57BL/6J mice were placed on low- (0.4), normal- (1.5), or high- (3 g/kg) Na chow at weaning (PD22) and continued on the diet for 3 wk (to PD40). Body composition and fluid distribution were determined serially by time-domain NMR and bioimpedance spectroscopy, and anxiety, learning, and memory were assessed using the elevated plus maze and Morris water maze paradigms in later adulthood (PD63-PD69). During the diet intervention, body mass gains were suppressed in the low- compared with normal- and high-Na groups despite similar caloric uptake rates across groups. Fat mass was reduced in males but not in females fed low-Na diet. Fat-free mass and hydration were significantly reduced in both males and females fed the low-Na diet, although rapidly corrected after return to normal diet. Measures of anxiety-like behavior and learning in adulthood were not affected by diet in either sex, yet memory performance was modified by a complex interaction between sex and early life Na intake. These data support the concepts that Na deficiency impairs growth and that the amount of Na intake which supports optimal somatic growth during early life may be insufficient to fully support neurocognitive development.

Venlafaxine Attenuated the Cognitive and Memory Deficit in Mice Exposed to Isoflurane Alone

Post-operative cognitive dysfunction (POCD) is a common complication during the post-operative period. It affects the recovery time of the patient after surgery and the stay time in hospital, which causes a great deal of burden to patients and families emotionally and financially. However, there is no specific and effective treatment available for this disorder. Recent study indicated exposure to general anesthetics contributed to POCD by triggering gamma-amino butyric acid type A (GABA_A) receptors hyperactivities that persisted even the anesthetic compounds have been eliminated. Here, we investigated the antidepressant, venlafaxine (VLX), in a mouse model of POCD and studied whether VLX attenuated the cognitive dysfunction of mice exposed to general anesthetic, isoflurane (ISO). We found that ISO significantly induced an increased surface expression of the GABA_A receptor subunit, α5, in the hippocampus of the mice. However, VLX treatment reduced the increase in α5 subunit expression. Meanwhile, we found the expression levels of interleukin (IL)-1β, tumor necrosis factor alpha (TNF-α), and IL-6 in the brains of mice exposed to ISO were significantly increased. However, VLX could prevent the increase in these cytokines. We also investigated the memory deficit of these mice by using a Y maze behavioral test. Mice with ISO exposure showed decreased alternation performance that could be prevented by the VLX treatment. Collectively, our results here are in line with the previous findings that α5 subunit plays an important role of the formation of POCD, but VLX may be a promising candidate compound for the treatment of POCD.

Isoflurane triggers the acute cognitive impairment of aged rats by damaging hippocampal neurons via the NR2B/CaMKII/CREB pathway

Isoflurane was responsible for acute neuronal impairment, but its potential molecular mechanisms in damaging hippocampal neurons had not been clearly understood. This study aimed to explore the underlying mechanism of how isoflurane affected the cognitive function of aged rats by damaging the hippocampal neurons. Acute cognitive impairment was found in aged Wistar rats via Morris water maze test and Y-maze test after isoflurane anesthesia in a dose-dependent manner compared with the control group in vivo. Isoflurane also decreased the viabilities and strengthened the apoptotic potential of hippocampal neurons by damaging the mitochondria in a time-dependent manner compared with the control group which was reported by MTT, immunofluorescent assay, flow cytometry and western blot assay in vitro. Isoflurane jeopardized hippocampal neurons by directly inactivating the NR2B/CaMKII/CREB pathway and its harmful effects could be ameliorated by adding CaMKII activator CdCl₂. These findings provided evidence that the cognitive ability of aged rats was injured by isoflurane exposure and isoflurane also inhibited the viability and enhanced the apoptosis of hippocampal neurons by damaging the mitochondria through inhibition of the NR2B/CaMKII/CREB pathway and its harmful roles could be partially ameliorated by CdCl₂. Our study demonstrated that isoflurane could cause acute neuronal damage and we provided fresh insights that contributed to the safe use of anesthetic agents and the prevention of PND in elderly people.

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.

Interoceptive Insular Cortex Mediates Both Innate Fear and Contextual Threat Conditioning to Predator Odor

The insular cortex (IC), among other brain regions, becomes active when humans experience fear or anxiety. However, few experimental studies in rats have implicated the IC in threat responses. We have recently reported that inactivation of the primary interoceptive cortex (pIC) during pre-training, or the intra-pIC blockade of protein synthesis immediately after training, impaired the consolidation of auditory fear conditioning. The present study was designed to investigate the role of the pIC in innate and learned defensive responses to predator odor. Freezing behavior was elicited by single or repetitive exposures to a collar that had been worn by a domestic cat. Sessions were video-recorded and later scored by video observation. We found that muscimol inactivation of the pIC reduced the expression of freezing reaction in response to a single or repeated exposure to cat odor. We also found that pIC inactivation with muscimol impaired conditioning of fear to the context in which rats were exposed to cat odor. Furthermore, neosaxitoxin inactivation of the pIC resulted in a prolonged and robust reduction in freezing response in subsequent re-exposures to cat odor. In addition, freezing behavior significantly correlated with the neural activity of the IC. The present results suggest that the IC is involved in the expression of both innate and learned fear responses to predator odor.

A randomized trial of desflurane or sevoflurane on postoperative quality of recovery after knee arthroscopy

Background

Studies have described different recovery profiles of sevoflurane and desflurane typically early after surgery.

Methods

We conducted a randomized superiority trial to determine whether Overall Recovery 3 days after knee arthroscopy would be superior with desflurane. Adult participants undergoing knee arthroscopic surgery with general anesthesia were randomized to either desflurane or sevoflurane general anesthesia. Intraoperative and postoperative drugs and analgesics were administered at the discretion of the anesthesiologist. Postoperative quality of recovery was assessed using the “Postoperative Quality of Recovery Scale”. The primary outcome was Overall Recovery 3 days after surgery and secondary outcomes were individual recovery domains at 15 minutes, 40 minutes, 1 day, 3 days, 1 month, and 3 months. Patients and researchers were blinded.

Results

300 patients were randomized to sevoflurane or desflurane (age 51.7±14.1 vs. 47.3±13.5 years; duration of anesthesia 24.9±11.1 vs. 23.3±8.3 minutes). The proportion achieving baseline or better scores in all domains increased over the follow-up period in both groups but was not different at day 3 (sevoflurane 43% vs. desflurane 37%, p = 0.314). Similarly, rates of recovery increased over time in the five subdomains, with no differences between groups for physiological, p = 0.222; nociceptive, p = 0.391; emotive, p = 0.30; Activities-of-daily-living, p = 0.593; and cognitive recovery, p = 0.877.

Conclusion

No significant difference in the quality of recovery scale could be shown using sevoflurane or desflurane general anesthesia after knee arthroscopy in adult participants.

Desflurane impairs hippocampal learning on day 1 of exposure: a prospective laboratory study in rats

Background

Quick and complete recovery of cognitive function after general anesthesia is desirable, particularly for working-age patients. Desflurane is less likely to have long-term effects than older-generation inhalational anesthetics, however, its short-term effects have not been fully investigated. Our objective was to elucidate the short-term effects of desflurane exposure on learning and memory in young adult rats.

Methods

Seven-week old male Sprague–Dawley rats were exposed to air (control), or desflurane at 0.7 or 1.2 minimum alveolar concentration (MAC) for 2 h (day 0). The inhibitory avoidance (IA) test was performed on day 1 to delineate the effects on contextual learning. Separate groups of control and 1.2 MAC desflurane animals underwent the IA test on days 3 and 7 to examine the time-dependent changes. Because the IA test is known to be dependent on the long-term potentiation (LTP) of the hippocampus and the trafficking of the GluR1 subunit of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor into the synapses, the effects of 1.2 MAC desflurane on these phenomena were evaluated on day 1.

Results

Desflurane at 1.2 MAC, but not 0.7 MAC, significantly decreased the IA latencies on day 1 compared with the control (one-way ANOVA, F [2,48] = 5.974, P = 0.005, post hoc Tukey’s, mean difference [95% confidence interval], control vs. 1.2 MAC, 168 [49.9 to 287], P = 0.004; control vs. 0.7 MAC, 67.5 [− 51.2 to 186], P = 0.362). The latencies were not affected on days 3 and 7 (day 3, control vs. desflurane, P = 0.861; day 7, control vs. desflurane, P > 0.999). Consistently, hippocampal LTP on day 1 was significantly suppressed in the desflurane group compared with the control group (P = 0.006). Moreover, immunoblotting analysis of synaptic GluR1 expression revealed that desflurane exposure significantly suppressed GluR1 delivery to the synapses after IA training.

Conclusion

Exposure to a relatively high concentration of desflurane caused reversible learning and memory impairment in young adult rats associated with suppression of GluR1 delivery to the synapses in the hippocampus.

Effects of intrastriatal dopamine D1 or D2 antagonists on methamphetamine-induced egocentric and allocentric learning and memory deficits in Sprague-Dawley rats

RATIONALE

Methamphetamine (MA) is an abused psychostimulant that causes cognitive deficits after chronic use. Neostriatal dopamine receptors play a role in MA monoamine neurotoxicity. Blocking dopamine receptors prior to MA exposure in adult rats attenuates monoamine reductions and reactive gliosis.

OBJECTIVES

We tested whether blocking dopamine receptors protects against cognitive deficits.

METHODS

First, we determined the effects of MA alone versus MA in combination with the dopamine receptor D1 antagonist SCH-23390 or the dopamine receptor D2 antagonist sulpiride on cFos expression and monoamines at the age when rats in the cognitive experiment were to begin testing and monoamines in rats after cognitive testing.

RESULTS

SCH-23390 infused into the neostriatum prior to systemic administration of MA attenuated MA-induced cFos activation while sulpiride induced cFos activation. Two weeks after MA, rats had dopamine and serotonin reductions that were attenuated by each antagonist. Other rats treated the same way, were tested for egocentric learning and memory in the Cincinnati water maze, for navigational strategy in a star water maze, and spatial learning and memory in a Morris water maze. Pre-treatment with SCH-23390 or sulpiride attenuated the effects of MA on egocentric and spatial learning and memory. MA-treated rats showed a shift from an egocentric to a disorganized strategy in the star maze that was less disorganized in groups receiving MA and an antagonist. Post-behavior monoamine reductions remained but were attenuated by the antagonists but not identically to what was seen in rats not behaviorally tested.

CONCLUSIONS

The results show for the first time that dopamine receptors are mediators of MA-induced cognitive deficits.

microRNA-124 attenuates isoflurane-induced neurological deficits in neonatal rats via binding to EGR1

Isoflurane anesthesia induces neuroapoptosis in the development of the brain. In this study, neonatal rats and hippocampal neurons were subjected to isoflurane exposure, in which the effect of miR-124 on the neurological deficits induced by isoflurane was evaluated. Isoflurane anesthesia models were induced in neonatal SD rats aged 7 days and then treated with miR-124 agomir, miR-124 antagomir, or LV-CMV-early growth response 1 (EGR1) plasmids. Then, the spatial learning and memory ability of rats were evaluated by Morris water maze. Furthermore, primary hippocampal neurons cultured 7 days were also exposed to isoflurane and transfected with miR-124 agomir, miR-124 antagomir, or LV-CMV-EGR1 plasmids. The targeting relationship of miR-124 and EGR1 was verified by the dual-luciferase reporter gene assay. To identify the effect of miR-124 on neuron activities, the viability and apoptosis of hippocampal neurons were assessed. In response to isoflurane exposure, miR-124 expression was reduced and EGR1 expression was increased in the hippocampal tissues and neurons. The isoflurane anesthesia damaged rats' spatial learning and memory ability, and reduced viability, and promoted apoptosis of hippocampal neurons. EGR1 was targeted and negatively regulated by miR-124. The treatment of miR-124 agomir improved rats' spatial learning and memory ability and notably increased hippocampal neuron viability and resistance to apoptosis, corresponding to an increased brain-derived neurotrophic factor (BDNF) expression, inhibited expression of proapoptotic factors (cleaved-Caspase-3 and Bax), and enhanced the expression of antiapoptotic factor (Bcl-2). Upregulated miR-124 inhibited the expression of EGR1, by which mechanism miR-124 reduced the neurological deficits induced by isoflurane in neonatal rats through inhibiting apoptosis of hippocampal neurons.

The ventral hippocampus is involved in multi-goal obstacle-rich spatial navigation

A large body of evidence shows that the hippocampus is necessary for successful spatial navigation. Various studies have shown anatomical and functional differences between the dorsal (DHC) and ventral (VHC) portions of this structure. The DHC is primarily involved in spatial navigation and contains cells with small place fields. The VHC is primarily involved in context and emotional encoding contains cells with large place fields and receives major projections from the medial prefrontal cortex. In the past, spatial navigation experiments have used relatively simple tasks that may not have required a strong coordination along the dorsoventral hippocampal axis. In this study, we tested the hypothesis that the DHC and VHC may be critical for goal-directed navigation in obstacle-rich environments. We used a learning task in which animals memorize the location of a set of rewarded feeders, and recall these locations in the presence of small or large obstacles. We report that bilateral DHC or VHC inactivation impaired spatial navigation in both large and small obstacle conditions. Importantly, this impairment did not result from a deficit in the spatial memory for the set of feeders (i.e., recognition of the goal locations) because DHC or VHC inactivation did not affect recall performance when there was no obstacle on the maze. We also show that the behavioral performance of the animals was correlated with several measures of maze complexity and that these correlations were significantly affected by inactivation only in the large object condition. These results suggest that as the complexity of the environment increases, both DHC and VHC are required for spatial navigation.

Absence of Neuropathology With Prolonged Isoflurane Sedation in Healthy Adult Rats

BACKGROUND

The use of isoflurane sedation for prolonged periods in the critical care environment is increasing. However, isoflurane-mediated neurotoxicity has been widely reported. The goal of the present study was to determine whether long-term exposure to low-dose isoflurane in mechanically ventilated rodents is associated with evidence of neurodegeneration or neuroinflammation.

METHODS

Adult female Sprague-Dawley rats were used in this study. Experimental animals (n=11) were induced with 1.5% isoflurane, intubated, and given a neuromuscular blockade with α-cobratoxin. EEG electrodes were surgically implanted, subcutaneous precordial EKG Ag wire electrodes, and bladder, femoral artery, and femoral vein cannulas permanently placed. After these procedures, the isoflurane concentration was reduced to 0.5% and, in conjunction with the neuromuscular blockade, continued for 7 days. Arterial blood gases and chemistry were measured at 3 time points and core body temperature servoregulated and maintenance IV fluids were given during the 7 days. Experimental animals and untreated controls (n=9) were euthanized on day 7.

RESULTS

Immunohistochemical and cytochemical assays did not detect evidence of microgliosis, astrocytosis, neuronal apoptosis or necrosis, amyloidosis, or phosphorylated-tau accumulation. Blood glucose levels were significantly reduced on days 3/4 and 6/7 and partial pressure of oxygen was significantly reduced, but still within the normal range, on day 6/7. All other blood measurements were unchanged.

CONCLUSIONS

No neuropathologic changes consistent with neurotoxicity were detected in the brain after 1 week of continuous exposure to 0.5% isoflurane in healthy rats. These data suggest that even long exposures to low concentrations of isoflurane have no overt consequences on neuropathology.

Isoflurane Use in the Treatment of Super-Refractory Status Epilepticus is Associated with Hippocampal Changes on MRI

BACKGROUND

Refractory status epilepticus (RSE) is associated with high morbidity and mortality. Experts recommend aggressive management with continuous intravenous infusions or inhaled anesthetics such as isoflurane. However, there is concern that MRI changes in RSE reflect isoflurane neurotoxicity. We performed a case-control study to determine whether isoflurane is neurotoxic, based on MRI signal changes.

METHODS

We performed a retrospective case-control study of the incidence of MRI changes in RSE treated with and without isoflurane. Charts were reviewed for demographic and treatment information. T1, T2, and FLAIR sequences of MRIs were reviewed independently by two neuroradiologists blinded to treatment group for presence or absence of signal change or atrophy in the meninges, cortex, white matter, basal ganglia, thalamus, hippocampus, brainstem, and cerebellum.

RESULTS

Eight cases of RSE receiving treatment with isoflurane were identified and double-matched with 15 controls who received only intravenous anesthetics. Baseline characteristics were similar. Hippocampal signal change was observed more frequently in cases receiving isoflurane (p = 0.026).

CONCLUSIONS

Hippocampal signal changes were associated with isoflurane use in patients with RSE. They were also associated with number of seizure days prior to MRI and the use of multiple anesthetic agents. Similar changes have been seen as a result of RSE itself, and one cannot rule out the possibility these changes represent seizure-related effects. If isoflurane-related, these hippocampal signal changes may be the result of a direct neurotoxic effect of prolonged isoflurane use or failure of isoflurane to protect the hippocampus from seizure-induced injury despite achieving electrographic burst-suppression.

Central Disorders of Hypersomnolence, Restless Legs Syndrome, and Surgery With General Anesthesia: Patient Perceptions

Introduction: The importance of obstructive sleep apnea in patients undergoing surgery with general anesthesia is well-defined, but the surgical and anesthetic implications of other sleep disorders are less clear. We sought to evaluate response to surgery with general anesthesia in patients with central disorders of hypersomnolence or restless legs syndrome.

Methods: We surveyed patients on their most recent surgical procedure with general anesthesia, querying about procedure, recovery, and any changes in sleep disorder symptomatology following the procedure.

Results: Forty-five patients with restless legs syndrome and 57 patients with central disorders of hypersomnolence (15 narcolepsy type 2, 1 narcolepsy type 1, 30 idiopathic hypersomnia, 1 Kleine-Levin syndrome, and 10 subjective sleepiness) completed the survey, with response rates of 45.5 and 53.8%, respectively. While patients in both groups were equally likely to report surgical complications and difficulty awakening from anesthesia, hypersomnolent patients were more likely to report worsened sleepiness (40% of the hypersomnolent group vs. 11% of the RLS group, p = 0.001) and worsening of their sleep disorder symptoms (40% of the hypersomnolent group vs. 9% of the RLS group, p = 0.0001).

Conclusion: Patients with sleep disorders other than sleep apnea frequently report surgical or anesthetic complications. Patients with hypersomnolence disorders commonly perceive that their sleep disorder worsened following a procedure; whether this might be related to long term effects of general anesthesia in a particularly vulnerable clinical population requires further study.

Repeated exposure to sevoflurane impairs the learning and memory of older male rats

AIMS

Critically ill old patients sometimes require repeated surgical interventions, and thus it is important to determine the influence of repeated exposure to anesthetics on learning and memory. Sevoflurane, a widely used inhalation anesthetic, has few neurological adverse effects and offers a rapid return to consciousness. But the long-term influence of sevoflurane exposure and the effect of repeated sevoflurane exposure on cognition have rarely been reported, and available studies are contradictory.

MATERIALS AND METHODS

In the present study, the Morris water maze test was employed to investigate the long-term influence of single (4h) or repeated (2h daily for 5 consecutive days) exposure to 1.5% or 2.5% sevoflurane on the learning ability and memory of old (16-18months old) male rats. Testing was performed from 1day to 4weeks after the last exposure. In the hippocampus, brain derived neurotrophic factor (BDNF), NF-κB mRNA, and apoptosis rate were also examined to determine whether cellular biochemical changes related to cognition and memory occurred after single or repeated exposure to sevoflurane.

KEY FINDINGS

Repeated exposure to 2.5% sevoflurane decreased hippocampal levels of BDNF protein, enhanced hippocampal levels of NF-κB mRNA, and increased the apoptosis rate of pyramidal cells. Single exposure to 2.5% sevoflurane, and repeated exposure to either 1.5% or 2.5% sevoflurane significantly compromised learning and memory of old male rats.

SIGNIFICANCE

Repeated exposure to sevoflurane impaired the learning and memory of old male rats, an impairment that was accompanied by cognition-related biochemical changes in the hippocampus.

Apigenin attenuates isoflurane-induced cognitive dysfunction via epigenetic regulation and neuroinflammation in aged rats

PURPOSE OF THE RESEARCH

Post operational cognitive dysfunction (POCD) occurs in patients after anesthesia and surgery. Abnormal histone acetylation and neuroinflammation are key factors in the pathogenesis of cognitive impairment. Apigenin not only has an anti-inflammatory activity but also modifies histone acetylation. We aimed to investigate whether apigenin can attenuate isoflurane exposure-induced cognitive decline by regulating histone acetylation and inflammatory signaling.

MATERIALS AND METHODS

Spatial learning and memory were assessed by Morris water maze test. Levels of histone acetylation, BDNF and downstream signaling, and inflammatory components were analyzed.

PRINCIPAL RESULTS

Isoflurane exposure in aged rats lead to impaired spatial learning and memory. These rats exhibited dysregulated histone H3K9 and H4K12 acetylation, which was accompanied by reduced BDNF expression and suppressed BDNF downstream signaling pathway. Apigenin restored histone acetylation and BDNF signaling. Apigenin also suppressed isoflurane exposure induced upregulation of proinflammatory cytokines and NFκB signaling pathway.

MAJOR CONCLUSIONS

Memory impairment induced by isoflurane exposure is associated with dysregulated histone acetylation in the hippocampus, which affects BDNF expression and hence BDNF downstream signaling pathway. Apigenin recovers cognitive function by restoring histone acetylation and suppressing neuroinflammation.

Histamine H3 Receptor Antagonist Prevents Memory Deficits and Synaptic Plasticity Disruption Following Isoflurane Exposure

BACKGROUND

Exposure to pharmacological concentration of inhaled anesthetics such as isoflurane can cause short- or long-term cognitive impairments in preclinical studies. The selective antagonists of the histamine H3 receptors are considered as a promising group of novel therapeutic agents for the treatment of cognitive disorders. In this study, we investigated whether ciproxifan, a nonimidazole antagonist of H3 histamine receptors, could overcome the functional and electrophysiological sequela associated with isoflurane anesthesia.

METHODS

Adult male Sprague Dawley rats were exposed to 1.4% isoflurane or vehicle gas for 2 h. The memory tests (novel object recognition and passive avoidance) as well as in vivo hippocampal excitatory synaptic potentials were recorded 24 h postanesthesia. Locomotor activity, anxiety, and nociception 24 h after isoflurane were also examined. The drugs (ciproxifan 3 mg/kg or saline) were intraperitoneally injected 30 min prior to the behavioral tests or long-term potentiation induction.

RESULTS

Animals that were previously (24 h) exposed to 1.4% isoflurane for 2 h displayed no preference for novel objects and had impaired retention of a passive avoidance response at 1 h after sample phase. Treating isoflurane-exposed rats with ciproxifan significantly improved the memory performance, as evidenced by an increased discrimination ratio in objects recognition and prolonged retention time in passive avoidance test. Accordingly, hippocampus long-term potentiation was reduced in animals that received isoflurane, while administration of ciproxifan completely abolished the effect of isoflurane exposure on synaptic plasticity. Neither isoflurane nor ciproxifan altered motor performance, anxiety, and nociceptive responses.

CONCLUSION

These results suggest that H3R in the CNS, probably in the hippocampus, may serve as therapeutic target for improvement of anesthesia-associated cognitive deficits.

Impact of Methylprednisolone on Postoperative Quality of Recovery and Delirium in the Steroids in Cardiac Surgery Trial

Background

Inflammation after cardiopulmonary bypass may contribute to postoperative delirium and cognitive dysfunction. The authors evaluated the effect of high-dose methylprednisolone to suppress inflammation on the incidence of delirium and postoperative quality of recovery after cardiac surgery.

Methods

Five hundred fifty-five adults from three hospitals enrolled in the randomized, double-blind Steroids in Cardiac Surgery trial were randomly allocated to placebo or 250 mg methylprednisolone at induction and 250 mg methylprednisolone before cardiopulmonary bypass. Each completed the Postoperative Quality of Recovery Scale before surgery and on days 1, 2, and 3 and 1 and 6 months after surgery and the Confusion Assessment Method scale for delirium on days 1, 2, and 3. Recovery was defined as returning to preoperative values or improvement at each time point.

Results

Four hundred eighty-two participants for recovery and 498 participants for delirium were available for analysis. The quality of recovery improved over time but without differences between groups in the primary endpoint of overall recovery (odds ratio range over individual time points for methylprednisolone, 0.39 to 1.45; 95% CI, 0.08–2.04 to 0.40–5.27; P = 0.943) or individual recovery domains (all P > 0.05). The incidence of delirium was 10% (control) versus 8% (methylprednisolone; P = 0.357), with no differences in delirium subdomains (all P > 0.05). In participants with normal (51%) and low baseline cognition (49%), there were no significant differences favoring methylprednisolone in any domain (all P > 0.05). Recovery was worse in patients with postoperative delirium in the cognitive (P = 0.004) and physiologic (P < 0.001) domains.

Conclusions

High-dose intraoperative methylprednisolone neither reduces delirium nor improves the quality of recovery in high-risk cardiac surgical patients.

Anesthetic Isoflurane Induces DNA Damage Through Oxidative Stress and p53 Pathway

DNA damage is associated with aging and neurological disorders, including Alzheimer's disease. Isoflurane is a commonly used anesthetic. It remains largely unknown whether isoflurane induces DNA damage. Phosphorylation of the histone protein H2A variant X at Ser139 (γH2A.X) is a marker of DNA damage. We therefore set out to assess the effects of isoflurane on γH2A.X level in H4 human neuroglioma cells and in brain tissues of mice. Oxidative stress, caspase-activated DNase (CAD), and the p53 signaling pathway are involved in DNA damage. Thus, we determined the interaction of isoflurane with reactive oxygen species (ROS), CAD, and p53 to illustrate the underlying mechanisms. The cells were treated with 2 % isoflurane for 3 or 6 h. The mice were anesthetized with 1.4 % isoflurane for 2 h. Western blot, immunostaining and live cell fluorescence staining were used in the experiments. We showed that isoflurane increased levels of γH2A.X, cleaved caspase-3, and nucleus translocation of CAD and decreased levels of inhibitor of CAD (ICAD) and p53. Isoflurane enhanced the nucleus level of γH2A.X. Moreover, caspase inhibitor Z-VAD and ROS generation inhibitor N-acetyl-L-cysteine (NAC) attenuated the isoflurane-induced increase in γH2A.X level. However, NAC did not significantly alter the isoflurane-induced reduction in p53 level. Finally, p53 activator (actinomycin D) and inhibitor (pifithrin-α) attenuated and potentiated the isoflurane-induced increase in γH2A.X level, respectively. These findings suggest that isoflurane might induce DNA damage, as represented by increased γH2A.X level, via induction of oxidative stress and inhibition of the repair of DNA damage through the p53 signaling pathway.

Erythropoietin diminishes isoflurane-induced apoptosis in rat frontal cortex

BACKGROUND

During the brain growth spurt, anesthetic drugs can cause cellular and behavioral changes in the developing brain. The aim of this study was to determine the neuroprotective effect of erythropoietin after isoflurane anesthesia in rat pups.

METHODS

A total of 42, 7-day-old Wistar rats were divided into three groups. Control group (GC; n = 14): Rats breathed 100% oxygen for 6 h; Isoflurane group (GI; n = 14): Rats were exposed to 1.5% isoflurane in 100% oxygen for 6 h; Isoflurane + erythropoietin group (GIE; n = 14): 1000 IU·kg(-1) (intraperitoneal; IP) Erythropoietin was administered after isoflurane anesthesia. Each group was divided into two groups for pathology and learning and memory tests. Silver, caspase-3, and fluoro-jade C staining were used for detecting apoptotic cells in frontal cortex, striatum, hippocampus, thalamus, and amygdala. Morris water maze was used to evaluate learning and memory.

RESULTS

There was a significant increase in apoptotic cell count after isoflurane anesthesia in the frontal cortex when compared with control group (29.0 ± 9.27 vs 3.28 ± 0.75 [P = 0.002], 20.85 ± 10.94 vs 2.0 ± 0.81 [P = 0.002] and 24.57 ± 10.4 vs 5.14 ± 0.69 [P = 0.024] with silver, caspase-3, and fluoro-jade C staining, respectively). The apoptotic cell count in the frontal cortex was significantly higher in GIE than GC with caspase-3 staining (9.14 ± 3.13 vs 2.0 ± 0.81, P = 0.002). The apoptotic cell count in GIE was significantly reduced in the frontal cortex when compared with GI (4.0 ± 0.81 vs 29.0 ± 9.27 [P = 0.002], 9.14 ± 3.13 vs 20.85 ± 10.94 [P = 0.04] and 4.0 ± 1.63 vs 24.57 ± 10.4 [P = 0.012] with silver, caspase-3, and fluoro-jade C staining, respectively).

CONCLUSIONS

A total of 1000 IU·kg(-1) IP erythropoietin diminished isoflurane-induced neuroapoptosis. Further experimental studies have to be planned to reveal the optimal dose and timing of erythropoietin before adaptation to clinical practice.

Novel intrathecal and subcutaneous catheter delivery systems in the mouse

BACKGROUND

Catheter systems that permit targeted delivery of genes, molecules, ligands, and other agents represent an investigative tool critical to the development of clinically relevant animal models that facilitate the study of neurological health and disease. The development of new sustained catheter delivery systems to spinal and peripheral sites will reduce the need for repeated injections, while ensuring constant levels of drug in plasma and tissues.

NEW METHOD

Here, we introduce two novel catheter delivery systems in the mouse: the O'Buckley intrathecal catheter system for sustained delivery to the spinal region and a subcutaneous bifurcated catheter system for sustained drug delivery to both hindpaws.

RESULTS

The O'Buckley intrathecal catheter system consistently distributed Evans Blue throughout the spinal cord, with the greatest concentration at the thoracic region, and with an 85% surgery success rate. The subcutaneous catheter system consistently distributed Evans Blue to the hindlimbs, with a 100% surgery success rate.

COMPARISON TO EXISTING METHOD

The O'Buckley intrathecal catheter system accomplishes sustained drug delivery to the spinal region, with a 2-fold increase in surgery success rate, as compared to the traditional method. Our subcutaneous bifurcated catheter system accomplishes sustained drug delivery to both hindpaws, eliminating the need for repeated intraplantar injections.

CONCLUSIONS

We have developed catheter systems that improve upon traditional methods in order to achieve sustained localized drug delivery to spinal tissues and to hindpaw tissues surrounding peripheral sciatic nerve terminals. These methods have a broad reach, and can be used to enhance behavioral, physiologic and mechanistic studies in mice.

Isoflurane in the presence or absence of surgery increases hippocampal cytokines associated with memory deficits and responses to brain injury in rats

Evidence from experimental animal studies convincingly argues for a role of pro-inflammatory cytokines due to surgical trauma in causing postoperative cognitive dysfunction. However, other studies have shown exposure to 2-4h of isoflurane anesthetic without surgical trauma can also impair cognitive function. We aimed to determine cytokine changes over time following isoflurane exposure in the presence and absence of surgery and examine subsequent cognitive function. Male rats were exposed to isoflurane (1.8%, 4h) with or without laparotomy or control conditions and tested in a contextual fear conditioning paradigm 8 days later. On day 9 rats were perfused, serum and hippocampal samples were collected and 24 cytokines were analysed. Groups of rats exposed as above were killed 6 or 48h after isoflurane exposure to examine early cytokine changes. Isoflurane exposure resulted in significantly less freezing in the contextual fear conditioning test (F(2,31)=6.11, P=0.006) and addition of laparotomy caused no further deficits (P>0.05). At 6h post isoflurane exposure an immunosuppressive response was observed in the serum while hippocampal cytokines were largely unchanged. These finding suggest isoflurane alone causes inflammatory changes and cognitive deficits. The addition of a laparotomy had a negligible effect. Early after isoflurane exposure changes in serum and hippocampal cytokines were divergent but by 9 days were aligned. At this time cytokines associated with memory deficits and brain injury processes were significantly elevated in serum and brain.

Impaired acquisition of conditioned taste aversion memory induced by isoflurane is accompanied with calcineurin activation and Egr-1 down-regulation in amygdala in rats

Compared to neutral memory, emotional memory is extremely strong and persistent immediately after acquisition, therefore it may recruit specific mechanisms during acquisition. The calcineurin-dependent mechanisms engaging early growth response 1 (Egr-1) have been proved to determine the strength of emotional memory during establishment. Isoflurane, a widely used inhalation anesthetic, can interfere with the acquisition of emotional memory. We hypothesized that isoflurane impairs the acquisition of conditioned taste aversion (CTA) memory in rats and the Egr-1 expression regulation via calcineurin (CaN) and ERK signaling pathway is involved in isoflurane-induced repression of CTA memory. To examine this, we investigated the influence of isoflurane on CTA memory and the expression and activity of CaN, the phosphorylation level of ERK and the expression of Egr-1 in amygdala in response to CTA training in rats. The results showed that isoflurane exposure (1.5%, 2h) before training impaired the acquisition of CTA memory in rats. Isoflurane exposure increased the CaN activity and decreased the p-ERK and Egr-1 in amygdala in rats. These findings suggest that isoflurane can disrupt the establishment of aversion memory, and CaN activation associating with p-ERK and Egr-1 down-regulation may contribute to the isoflurane induced impairment of aversion memory acquisition.

Effect of dexmedetomidine on early postoperative cognitive dysfunction and peri-operative inflammation in elderly patients undergoing laparoscopic cholecystectomy

The use of intravenous dexmedetomidine during surgery has been shown to suppress inflammatory cytokines peri-operatively. It has also been demonstrated that dexmedetomidine may benefit cognitive function in elderly patients following surgery; however, it is not clear whether dexmedetomidine reduces postoperative cognitive dysfunction (POCD) via the suppression of inflammatory cytokines. The aim of the present study was to investigate the effects of dexmedetomidine on early POCD and inflammatory cytokines in elderly patients undergoing laparoscopic cholecystectomy (LC). The study comprised 120 elderly patients undergoing selective LC, who were randomly allocated to receive either dexmedetomidine intravenously (DEX group, n=60) or the same volume of normal saline (control group, n=60). Cognitive function was assessed by Mini-Mental State Examination (MMSE) scores 1 day prior to surgery, 6 h following surgery and postoperatively on days 1 and 2. Interleukin (IL)-1β, IL-6 and C-reactive protein (CRP) levels were also measured at these time-points. On the basis of whether the patients had POCD on the first day after surgery, patients were divided into a POCD group and a non-POCD group. Blood cytokine levels were compared between the patients with and without POCD. A total of 100 patients completed both pre- and postoperative MMSE tests. At 1 day following surgery, POCD occurred in 10/50 (20%) patients in the DEX group and in 21/50 (42%) patients in the control group (P=0.017). At 6 h following surgery, IL-1β, IL-6 and CRP levels showed significant increases (P<0.01) compared with the baseline levels in the two groups. Furthermore, in the control group, CRP levels showed a significant increase on day 1 (P<0.001) and day 2 (P=0.017) postoperatively. In the DEX group compared with the control group, IL-1β, IL-6 and CRP levels were markedly decreased at 6 h and 1 day after surgery (P<0.01). Concentrations of IL-1β, IL-6 and CRP were significantly higher in patients who developed POCD on day 1 following surgery than in the patients who did not develop POCD (P<0.05). The findings of the current study support the hypothesis that dexmedetomidine administration during anesthesia decreases the incidence of early POCD, most likely by the mechanism of reduction of the inflammatory response level.

The role of hippocampal tau protein phosphorylation in isoflurane-induced cognitive dysfunction in transgenic APP695 mice

BACKGROUND

Previous studies have shown that exposure to inhaled anesthetics can cause cognitive dysfunction, suggesting that general anesthesia might be a risk factor for the development of Alzheimer disease. However, the underlying mechanisms remain to be elucidated. In the present study, we tested our hypothesis that enhanced tau protein phosphorylation in hippocampus contributes to isoflurane-induced cognitive dysfunction in a mouse model of Alzheimer disease.

METHODS

Fifty-four male wild-type (WT) mice (12 months old) and 54 male amyloid precursor protein 695 (APP695) mice (12 months old) were either anesthetized for 4 hours with 1.0 minimum alveolar concentration isoflurane or sham-anesthetized (control). Learning and memory behaviors were measured using the Morris Water Maze test for mice. Phosphorylation of hippocampal tau protein at Ser262 site was analyzed with quantitative Western blotting.

RESULTS

In the Morris Water Maze test, both WT and transgenic APP695 mice showed decreased latency times during a 4-day training period. Isoflurane exposure significantly increased the latency times on days 2 and 3 in WT mice as well as on days 3 and 4 in APP695 mice (WT: P = 0.005 for day 2 and P = 0.002 for day 3; APP695: P = 0.001 for day 3 and P < 0.0001 for day 4) and reduced platform quadrant times (WT: P < 0.0001; APP695: P < 0.0001) in both types of mice. Compared with WT mice, transgenic APP695 mice displayed worse learning and memory behaviors after isoflurane exposure (P = 0.0005 for escape latency testing on day 4 training; P = 0.009 for platform probe testing). Western blot analysis showed that the levels of phosphorylation of hippocampal tau protein at Ser262 site (tau[pS262]) in the transgenic APP695 mice were higher than those in WT mice (P < 0.0001) and that isoflurane exposure time dependently enhanced the hippocampal tau[pS262] levels in both types of mice, but this effect was much more significant in the transgenic APP695 mice (P < 0.0001). Our data also showed that isoflurane exposure had no effect on the expression of total tau protein in the hippocampi of all mice (P ≥ 0.54).

CONCLUSIONS

Isoflurane may induce cognitive dysfunction by enhancing phosphorylation of hippocampal tau protein at Ser262 site, and this effect is more significant in transgenic APP695 mice.

Knee surgery recovery: Post-operative Quality of Recovery Scale comparison of age and complexity of surgery

BACKGROUND

Initial validation and feasibility for the Post-operative Quality of Recovery Scale (PQRS) was published in 2010. Ongoing validation includes studies to determine whether this scale can discriminate differences in recovery between cohorts.

METHODS

A prospective cohort study included 61 patients, 18-40 years, and 61 patients, aged ≥ 65 years, undergoing knee arthroscopy under general anaesthesia; and 13 patients, aged ≥ 65 years, undergoing total knee replacement under general anaesthesia. Patients were assessed using the PQRS. Assessments were performed pre-surgery, at 15 and 40 min, 1 and 3 days, and 3 months after surgery.

RESULTS

The effect of age was assessed by comparing young versus older arthroscopy patients. There were minimal differences in recovery profiles, other than for the nociceptive domain, where pain recovery was significantly better in the older arthroscopy patients (P < 0.001). The effect of surgery was assessed by comparing older patients undergoing knee arthroscopy with knee replacement patients. Recovery was significantly worse for the knee replacement group for cognition (P = 0.015), nociception (pain and nausea, P < 0.001), activities of daily living (P < 0.001), emotive recovery (P = 0.029), and all-domains recovery (P < 0.001). Despite differences in quality of recovery, satisfaction was high in all cohorts.

CONCLUSIONS

Knee replacement had a large effect on recovery compared with knee arthroscopy. Age had minimal effect on recovery after knee arthroscopy. The study showed the ability of the PQRS to discriminate recovery in different domains.

Emulsified isoflurane anesthesia decreases brain-derived neurotrophic factor expression and induces cognitive dysfunction in adult rats

Post-operative cognitive dysfunction (POCD) is a severe complication characterized by cognitive decline in patients following anesthesia and surgery. Previous studies have suggested that volatile anesthetics, for example isoflurane, may contribute to such impairment. In the present study, the effects of emulsified isoflurane (EI) exposure on cognitive function, as well as the potential mechanisms, were investigated in animal models. Eight-month-old male rats were administered a single intravenous injection of 8% EI. The rats were then subjected to the Morris water maze test to assess their cognitive functions at different time-points following drug administration. Samples were taken in order to detect the plasma corticosterone concentration and the levels of hippocampal brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF), as well as the expression of BDNF and NGF in the hippocampal region. The results showed that a single injection of EI caused reversible learning and memory dysfunction in adult rats. It was found that downregulation of BDNF expression may contribute to the isoflurane-induced cognitive impairment of these rats. Increased expression of NGF may be associated with the protection mechanism subsequent to learning and memory function decline, and therefore may accelerate the recovery of cognitive function.

Activation of the canonical nuclear factor-κB pathway is involved in isoflurane-induced hippocampal interleukin-1β elevation and the resultant cognitive deficits in aged rats

Although much recent evidence has demonstrated that neuroinflammation contributes to volatile anesthetic-induced cognitive deficits, there are few existing mechanistic explanations for this inflammatory process. This study was conducted to investigate the effects of the volatile anesthetic isoflurane on canonical nuclear factor (NF)-κB signaling, and to explore its association with hippocampal interleukin (IL)-1β levels and anesthetic-related cognitive changes in aged rats. After a 4-h exposure to 1.5% isoflurane in 20-month-old rats, increases in IκB kinase and IκB phosphorylation, as well as a reduction in the NF-κB inhibitory protein (IκBα), were observed in the hippocampi of isoflurane-exposed rats compared with control rats. These events were accompanied by an increase in NF-κB p65 nuclear translocation at 6h after isoflurane exposure and hippocampal IL-1β elevation from 1 to 6h after isoflurane exposure. Nevertheless, no significant neuroglia activation was observed. Pharmacological inhibition of NF-κB activation by pyrrolidine dithiocarbamate markedly suppressed the IL-1β increase and NF-κB signaling, and also mitigated the severity of cognitive deficits in the Morris water maze task. Overall, our results demonstrate that isoflurane-induced cognitive deficits may stem from upregulation of hippocampal IL-1β, partially via activation of the canonical NF-κB pathway, in aged rats.

Clinical correlates in an experimental model of repetitive mild brain injury

OBJECTIVE

Although there is growing awareness of the long-term cognitive effects of repetitive mild traumatic brain injury (rmTBI; eg, sports concussions), whether repeated concussions cause long-term cognitive deficits remains controversial. Moreover, whether cognitive deficits depend on increased amyloid β deposition and tau phosphorylation or are worsened by the apolipoprotein E4 allele remains unknown. Here, we use an experimental model of rmTBI to address these clinical controversies.

METHODS

A weight drop rmTBI model was used that results in cognitive deficits without loss of consciousness, seizures, or gross or microscopic evidence of brain damage. Cognitive function was assessed using a Morris water maze (MWM) paradigm. Immunostaining and enzyme-linked immunosorbent assay (ELISA) were used to assess amyloid β deposition and tau hyperphosphorylation. Brain volume and white matter integrity were assessed by magnetic resonance imaging (MRI).

RESULTS

Mice subjected to rmTBI daily or weekly but not biweekly or monthly had persistent cognitive deficits as long as 1 year after injuries. Long-term cognitive deficits were associated with increased astrocytosis but not tau phosphorylation or amyloid β (by ELISA); plaques or tangles (by immunohistochemistry); or brain volume loss or changes in white matter integrity (by MRI). APOE4 was not associated with worse MWM performance after rmTBI.

INTERPRETATION

Within the vulnerable time period between injuries, rmTBI produces long-term cognitive deficits independent of increased amyloid β or tau phosphorylation. In this model, cognitive outcome is not influenced by APOE4 status. The data have implications for the long-term mental health of athletes who suffer multiple concussions.

Potentiation of GABAA receptor activity by volatile anaesthetics is reduced by α5GABAA receptor-preferring inverse agonists

BACKGROUND

Animal studies have shown that memory deficits in the early post-anaesthetic period can be prevented by pre-treatment with an inverse agonist that preferentially inhibits α5 subunit-containing γ-aminobutyric acid type A (α5GABA(A)) receptors. The goal of this in vitro study was to determine whether inverse agonists that inhibit α5GABA(A) receptors reduce anaesthetic potentiation of GABAA receptor activity.

METHODS

Cultures of hippocampal neurones were prepared from Swiss white mice, wild-type mice (genetic background C57BL/6J and Sv129Ev) and α5GABA(A)receptor null mutant (Gabra5-/-) mice. Whole-cell voltage clamp techniques were used to study the effects of the α5GABA(A) receptor-preferring inverse agonists L-655,708 and MRK-016 on anaesthetic potentiation of GABA-evoked currents.

RESULTS

L-655,708 (50 nM) reduced sevoflurane potentiation of GABA-evoked current in wild-type neurones but not Gabra5-/- neurones, and produced a rightward shift in the sevoflurane concentration-response plot [sevoflurane EC50: 1.9 (0.1) mM; sevoflurane+L-655,708 EC(50): 2.4 (0.2) mM, P<0.05]. Similarly, L-655,708 (50 nM) reduced isoflurane potentiation of GABA-evoked current [isoflurane: 4.0 (0.6) pA pF(-1); isoflurane+L-655,708: 3.1 (0.5) pA pF(-1), P<0.01]. MRK-016 also reduced sevoflurane and isoflurane enhancement of GABA-evoked current [sevoflurane: 1.5 (0.1) pA pF(-1); sevoflurane+MRK-016 (10 nM): 1.2 (0.1) pA pF(-1), P<0.05; isoflurane: 3.5 (0.3) pA pF(-1); isoflurane+MRK-016 (1 nM): 2.9 (0.2) pA pF(-1), P<0.05].

CONCLUSIONS

L-655,708 and MRK-016 reduced the potentiation by inhaled anaesthetics of GABAA receptor activated by a low concentration of GABA. Future studies are required to determine whether this effect contributes to the memory preserving properties of inverse agonists after anaesthesia.

Dexmedetomidine may benefit cognitive function after laparoscopic cholecystectomy in elderly patients

Laparoscopic cholecystectomy is performed with increasing frequency in aging populations. However, in elderly patients, cognitive dysfunction following surgery may impair the outcome of surgical procedures. Dexmedetomidine (DEX) has been demonstrated to have a neuroprotectve effect in animal experiments. However, it is unclear whether DEX also has a neuroprotective effect in human patients. The present study was a randomized, placebo-controlled double-blind trial of 126 patients who had undergone laparoscopic cholecystectomy, using clinical interviews to determine whether intravenously administrated DEX during general anesthesia ameliorates cognitive function impairment. The cognitive deficit of each patient was assessed using the Mini-Mental State Examination (MMSE). The scores on the MMSE for the DEX and control groups one week after surgery (DEX group, 27.6±1.2; control group, 25.7±1.5) were significantly different (P=0.005). The MMSE scores of patients ≤65 years old were significantly higher than those of patients >65 one week after surgery. The MMSE scores were significantly different between the two age groups in the control patients (≤65 years old, 28.3±1.2; >65 years old, 26.6±2.1; P=0.036), while the difference was not statistically significant in the DEX-treated patients. Eight patients in the DEX group and 15 patients in the control group had mild cognitive impairment (26≥ MMSE score ≥21) although the difference was not statistically significant. The findings of the present study support the hypothesis that DEX administration may be an effective method for ameliorating postoperative cognitive impairment in elderly patients who have undergone laparoscopic cholecystectomy. Further research is required to confirm the findings of the present study.