Anesthetic Sensitivity Research Articles

Monosodium glutamate disrupts zebrafish sleep-like state likely through activation of peripheral nervous system glutamate receptors

Monosodium glutamate (MSG), a widely used flavor enhancer, has raised concerns about its effects on behavior and sleep. This study investigates how MSG influences zebrafish sleep-like state (SLS) and interacts with other substances affecting neurobehavioral responses. Adult zebrafish were exposed to MSG at concentrations of 50, 100, and 150 mg/L, and their swimming speeds and SLS durations were recorded over a 14-hour night period. The results indicated that higher MSG concentrations increased swimming speeds and decreased SLS duration, suggesting heightened excitability and reduced sleep recovery. The study further evaluated how MSG impacts anesthesia sensitivity induced by 2-phenoxyethanol (POE) compared to alcohol and nicotine. Zebrafish were pre-treated with 50 mg/L MSG, 0.5% alcohol, or 0.5 mg/L nicotine before being anesthetized with POE. Nicotine decreased anesthesia sensitivity in a concentration-dependent manner by enhancing neurotransmitter release. In contrast, MSG and alcohol had minimal effects on anesthesia. The limited impact of MSG on anesthesia sensitivity suggests that MSG primarily affects peripheral nervous system functions rather than central nervous system functions, likely due to its poor ability to cross the blood-brain barrier. Overall, the findings demonstrate that MSG disrupts zebrafish behavior through peripheral mechanisms, affecting both swimming activity and sleep patterns. Nicotine, on the other hand, influences behavior through central nervous system interactions. These results highlight the need for further research to better understand how dietary additives like MSG impact neurobehavioral functions in aquatic models, offering insights into their broader implications for sleep and behavior.

You Don't Always Get What You Want!

Mutations in several genes of Caenorhabditis elegans confer altered sensitivities to volatile anesthetics. A mutation in one gene, gas-1(fc21), causes animals to be immobilized at lower concentrations of all volatile anesthetics than in the wild type, and it does not depend on mutations in other genes to control anesthetic sensitivity. gas-1 confers different sensitivities to stereoisomers of isoflurane, and thus may be a direct target for volatile anesthetics. The authors have cloned and characterized the gas gene and the mutant allele fc21. Genetic techniques for nematodes were as previously described. Polymerase chain reaction, sequencing, and other molecular biology techniques were performed by standard methods. Mutant rescue was done by injecting DNA fragments into the gonad of mutant animals and scoring the offspring for loss of the mutant phenotype. The gas-1 gene was cloned and identified. The protein GAS-1 is a homologue of the 49-kd (IP) subunit of the mitochondrial NADH-ubiquinone-oxidoreductase (complex I of the respiratory chain). gas-1(fc21) is a missense mutation replacing a strictly conserved arginine with lysine. The function of the 49-kd (IP) subunit of complex I is unknown. The finding that mutations in complex I increase sensitivity of C. elegans to volatile anesthetics may implicate this physiologic process in the determination of anesthetic sensitivity. The hypersensitivity of animals with a mutation in the gas-1 gene may be caused by a direct anesthetic effect on a mitochondrial protein or secondary effects at other sites caused by mitochondrial dysfunction.

Rényi entropy-complexity causality space: a novel neurocomputational tool for detecting scale-free features in EEG/iEEG data.

Scale-free brain activity, linked with learning, the integration of different time scales, and the formation of mental models, is correlated with a metastable cognitive basis. The spectral slope, a key aspect of scale-free dynamics, was proposed as a potential indicator to distinguish between different sleep stages. Studies suggest that brain networks maintain a consistent scale-free structure across wakefulness, anesthesia, and recovery. Although differences in anesthetic sensitivity between the sexes are recognized, these variations are not evident in clinical electroencephalographic recordings of the cortex. Recently, changes in the slope of the power law exponent of neural activity were found to correlate with changes in Rényi entropy, an extended concept of Shannon's information entropy. These findings establish quantifiers as a promising tool for the study of scale-free dynamics in the brain. Our study presents a novel visual representation called the Rényi entropy-complexity causality space, which encapsulates complexity, permutation entropy, and the Rényi parameter q. The main goal of this study is to define this space for classical dynamical systems within theoretical bounds. In addition, the study aims to investigate how well different time series mimicking scale-free activity can be discriminated. Finally, this tool is used to detect dynamic features in intracranial electroencephalography (iEEG) signals. To achieve these goals, the study implementse the Bandt and Pompe method for ordinal patterns. In this process, each signal is associated with a probability distribution, and the causal measures of Rényi entropy and complexity are computed based on the parameter q. This method is a valuable tool for analyzing simulated time series. It effectively distinguishes elements of correlated noise and provides a straightforward means of examining differences in behaviors, characteristics, and classifications. For the iEEG experimental data, the REM state showed a greater number of significant sex-based differences, while the supramarginal gyrus region showed the most variation across different modes and analyzes. Exploring scale-free brain activity with this framework could provide valuable insights into cognition and neurological disorders. The results may have implications for understanding differences in brain function between the sexes and their possible relevance to neurological disorders.

Nicotinamide Adenine Dinucleotide Does Not Improve Anesthetic Recovery in Rodents.

Nicotinamide Adenine Dinucleotide (NAD+) is implicated in bioenergetics, DNA repair, and senescence. Depletion of NAD+ is associated with aging and neurodegenerative disease, prompting a growing interest in NAD+ supplementation. With rising over-the-counter use of NAD, understanding their impact on perioperative recovery becomes essential. This study investigates the effect of NADH, a common NAD+ precursor, on anesthesia in rodents. Baseline and post-anesthesia (1.5% isoflurane) open field and Y-maze activity were recorded in adult male and female C57/BL6 mice (n = 8-10/group). NADH (150 mg/kg, intraperitoneal) or vehicle (0.9% normal saline) were given at baseline or during anesthesia. The NADH-treated group exhibited a significant decrease in open-field activity relative to vehicle-treated. This diminished activity was reflected in reduced distance travelled and average velocity after emergence from anesthesia in the NADH-treated group. NADH treatment did not improve Y-maze performance after anesthesia as the number of visits to the novel arm was significantly decreased. This study demonstrates a potentially adverse impact of NADH on recovery from anesthesia. We revealed a depression in open-field activity and Y-maze performance with NADH supplementation, an indicator of cognitive recovery in rodents. The broad implications of NAD+ in aging are likely to shape supplementation trends, highlighting the importance of understanding the potential influence of administering NAD+ on anesthetic sensitivity and recovery.

Sodium Leak Channel in Glutamatergic Neurons of the Lateral Parabrachial Nucleus Helps to Maintain Respiratory Frequency Under Sevoflurane Anesthesia.

The lateral parabrachial nucleus (PBL) is implicated in the regulation of respiratory activity. Sodium leak channel (NALCN) mutations disrupt the respiratory rhythm and influence anesthetic sensitivity in both rodents and humans. Here, we investigated whether the NALCN in PBL glutamatergic neurons maintains respiratory function under general anesthesia. Our results showed that chemogenetic activation of PBL glutamatergic neurons increased the respiratory frequency (RF) in mice; whereas chemogenetic inhibition suppressed RF. NALCN knockdown in PBL glutamatergic neurons but not GABAergic neurons significantly reduced RF under physiological conditions and caused more respiratory suppression under sevoflurane anesthesia. NALCN knockdown in PBL glutamatergic neurons did not further exacerbate the respiratory suppression induced by propofol or morphine. Under sevoflurane anesthesia, painful stimuli rapidly increased the RF, which was not affected by NALCN knockdown in PBL glutamatergic neurons. This study suggested that the NALCN is a key ion channel in PBL glutamatergic neurons that maintains respiratory frequency under volatile anesthetic sevoflurane but not intravenous anesthetic propofol.

Hormonal basis of sex differences in anesthetic sensitivity.

General anesthesia-a pharmacologically induced reversible state of unconsciousness-enables millions of life-saving procedures. Anesthetics induce unconsciousness in part by impinging upon sexually dimorphic and hormonally sensitive hypothalamic circuits regulating sleep and wakefulness. Thus, we hypothesized that anesthetic sensitivity should be sex-dependent and modulated by sex hormones. Using distinct behavioral measures, we show that at identical brain anesthetic concentrations, female mice are more resistant to volatile anesthetics than males. Anesthetic sensitivity is bidirectionally modulated by testosterone. Castration increases anesthetic resistance. Conversely, testosterone administration acutely increases anesthetic sensitivity. Conversion of testosterone to estradiol by aromatase is partially responsible for this effect. In contrast, oophorectomy has no effect. To identify the neuronal circuits underlying sex differences, we performed whole brain c-Fos activity mapping under anesthesia in male and female mice. Consistent with a key role of the hypothalamus, we found fewer active neurons in the ventral hypothalamic sleep-promoting regions in females than in males. In humans, we demonstrate that females regain consciousness and recover cognition faster than males after identical anesthetic exposures. Remarkably, while behavioral and neurocognitive measures in mice and humans point to increased anesthetic resistance in females, cortical activity fails to show sex differences under anesthesia in either species. Cumulatively, we demonstrate that sex differences in anesthetic sensitivity are evolutionarily conserved and not reflected in conventional electroencephalographic-based measures of anesthetic depth. This covert resistance to anesthesia may explain the higher incidence of unintended awareness under general anesthesia in females.

Bilirubin potentiates etomidate-induced sedation by enhancing GABA-induced currents after bile duct ligation

ObjectivesOur previous clinical trial showed that etomidate requirements to reach an appropriate level of anesthesia in patients with obstructive jaundice were reduced, which means that these patients are more sensitive to etomidate. However, the mechanism is still not completely clear. The present study was aimed to investigate the mechanism by which bilirubin facilitates etomidate induced sedation.MethodsA bile duct ligation (BDL) rat model was used to simulate obstructive jaundice. Anesthesia sensitivity to etomidate was determined by the time to loss of righting reflex (LORR). Intrathecal injection of bilirubin was used to test the effects of bilirubin on etomidate induced sedation. The modulating effects of bilirubin on GABA responses were studied using the whole-cell patch clamp technique.ResultsThe time to LORR induced by etomidate was significantly decreased in the BDL groups (p < 0.05), and unconjugated bilirubin in serum and cerebrospinal fluid (CSF) were markedly increased (p < 0.05). The time to LORR induced by etomidate was decreased after intrathecal injection of bilirubin (p < 0.05). A bilirubin concentration of 1.0 μM increased the GABA-induced currents of rat cortical pyramidal neurons (p < 0.05). Furthermore, 1.0 μM bilirubin enhanced GABA-induced currents modulated by etomidate (p < 0.05).ConclusionsOur results demonstrated that pathologic bilirubin in CSF could enhance etomidate induced sedation. The mechanism may be that bilirubin increase the GABA-induced currents of rat pyramidal neurons.

0042 EEP-PROMOTING GABAERGIC NEURONS IN THE PARAFACIAL ZONE PLAY A ROLE IN ANESTHETIC-INDUCED UNCONSCIOUSNESS IN MICE

Abstract Introduction Although the precise mechanisms by which anesthetics induce unconsciousness are unknown, there is evidence that shared brain circuits are engaged during sleep and general anesthesia. The parafacial zone (PZ) of the brainstem has recently been identified as a sleep-promoting region. Specifically, GABAergic neurons in the PZ (PZ-GABA) are active during non-REM sleep. The role of sleep-promoting PZ-GABA during anesthetic-induced hypnosis is unknown. We hypothesized that PZ-GABA are active during general anesthesia and contribute to anesthetic-induced hypnosis. Methods Adult C57BL6 mice (n = 3) were subjected to two-hour exposures of a hypnotic dose of an inhaled general anesthetic (isoflurane 1.2%) in oxygen, a non-immobilizer, F6, that lacks hypnotic properties (1,2-dicholorohexafluorocyclobutane 3%) in oxygen, or oxygen alone. The brains were harvested immediately following these exposures. The sections of brain were immunostained for c-Fos and GAD. To study the role of PZ-GABA in isoflurane-induced hypnosis, ablation of PZ-GABA was performed in adult bitransgenic Vgat-ires-Cre;Ai6 mice in which GABAergic neurons express a fluorescent reporter (n = 5 per group). Anesthesia sensitivity was evaluated weekly for four weeks after the virus injections by assessing the presence of a righting reflex during the exposures. Results In the PZ, a hypnotic dose of Isoflurane selectively activated GAD-positive GABAergic neurons compared to mice treated with F6 and oxygen. (P &amp;lt; 0.01 for both F6 and oxygen vs. Isoflurane, one-way ANOVA) Furthermore, mice lacking PZ-GABA demonstrated resistance to anesthetic induction, decreased sensitivity during the maintenance phase, and consistently increased the propensity to emerge from anesthesia. (For both induction and emergence, the upper 95% CI of EC50 at baseline was lower than the lower 95% CI at all time points after the injections. For maintenance phase, P &amp;lt; 0.05 for baseline vs. 1-week, one-way ANOVA) Conclusion PZ-GABA was active during isoflurane exposure. Moreover, the absence of PZ-GABA resulted in resistance to isoflurane-induced hypnosis. These findings suggest that PZ-GABA, a sleep-promoting region in the brainstem, plays an important role in general anesthesia. Support (if any) NIH (T32HL7713-27, T32 NS091006), ATS-ASPIRE

Oestrous cycle affects emergence from anaesthesia with dexmedetomidine, but not propofol, isoflurane, or sevoflurane, in female rats

BackgroundAlthough sex differences in anaesthetic sensitivity have been reported, what underlies these differences is unknown. In rodents, one source of variability in females is the oestrous cycle. Here we test the hypothesis that the oestrous cycle impacts emergence from general anaesthesia. MethodsTime to emergence was measured after isoflurane (2 vol% for 1 h), sevoflurane (3 vol% for 20 min), dexmedetomidine (50 μg kg−1 i.v., infused over 10 min), or propofol (10 mg kg−1 i.v. bolus) during proestrus, oestrus, early dioestrus, and late dioestrus in female Sprague–Dawley rats (n=24). EEG recordings were taken during each test for power spectral analysis. Serum was analysed for 17β-oestradiol and progesterone concentrations. The effect of oestrous cycle stage on return of righting latency was assessed using a mixed model. The association between righting latency and serum hormone concentration was tested by linear regression. Mean arterial blood pressure and arterial blood gases were assessed in a subset of rats after dexmedetomidine and compared in a mixed model. ResultsOestrous cycle did not affect righting latency after isoflurane, sevoflurane, or propofol. When in the early dioestrus stage, rats emerged more rapidly from dexmedetomidine than in the proestrus (P=0.0042) or late dioestrus (P=0.0230) stage and showed reduced overall power in frontal EEG spectra 30 min after dexmedetomidine (P=0.0049). 17β-Oestradiol and progesterone serum concentrations did not correlate with righting latency. Oestrous cycle did not affect mean arterial blood pressure or blood gases during dexmedetomidine. ConclusionsIn female rats, the oestrous cycle significantly impacts emergence from dexmedetomidine-induced unconsciousness. However, 17β-oestradiol and progesterone serum concentrations do not correlate with the observed changes.

TREK-1 and TREK-2 Knockout Mice Are Not Resistant to Halothane or Isoflurane.

A variety of molecular targets for volatile anesthetics have been suggested, including the anesthetic-sensitive potassium leak channel, TREK-1. Knockout of TREK-1 is reported to render mice resistant to volatile anesthetics, making TREK-1 channels compelling targets for anesthetic action. Spinal cord slices from mice, either wild type or an anesthetic- hypersensitive mutant, Ndufs4, display an isoflurane-induced outward potassium leak that correlates with their minimum alveolar concentrations and is blocked by norfluoxetine. The hypothesis was that TREK-1 channels conveyed this current and contribute to the anesthetic hypersensitivity of Ndufs4. The results led to evaluation of a second TREK channel, TREK-2, in control of anesthetic sensitivity. The anesthetic sensitivities of mice carrying knockout alleles of Trek-1 and Trek-2, the double knockout Trek-1;Trek-2, and Ndufs4;Trek-1 were measured. Neurons from spinal cord slices from each mutant were patch clamped to characterize isoflurane-sensitive currents. Norfluoxetine was used to identify TREK-dependent currents. The mean values for minimum alveolar concentrations (± SD) between wild type and two Trek-1 knockout alleles in mice (P values, Trek-1 compared to wild type) were compared. For wild type, minimum alveolar concentration of halothane was 1.30% (0.10), and minimum alveolar concentration of isoflurane was 1.40% (0.11); for Trek-1tm1Lex, minimum alveolar concentration of halothane was 1.27% (0.11; P = 0.387), and minimum alveolar concentration of isoflurane was 1.38% (0.09; P = 0.268); and for Trek-1tm1Lzd, minimum alveolar concentration of halothane was 1.27% (0.11; P = 0.482), and minimum alveolar concentration of isoflurane was 1.41% (0.12; P = 0.188). Neither allele was resistant for loss of righting reflex. The EC50 values of Ndufs4;Trek-1tm1Lex did not differ from Ndufs4 (for Ndufs4, EC50 of halothane, 0.65% [0.05]; EC50 of isoflurane, 0.63% [0.05]; and for Ndufs4;Trek-1tm1Lex, EC50 of halothane, 0.58% [0.07; P = 0.004]; and EC50 of isoflurane, 0.61% [0.06; P = 0.442]). Loss of TREK-2 did not alter anesthetic sensitivity in a wild-type or Trek-1 genetic background. Loss of TREK-1, TREK-2, or both did not alter the isoflurane-induced currents in wild-type cells but did cause them to be norfluoxetine insensitive. Loss of TREK channels did not alter anesthetic sensitivity in mice, nor did it eliminate isoflurane-induced transmembrane currents. However, the isoflurane-induced currents are norfluoxetine-resistant in Trek mutants, indicating that other channels may function in this role when TREK channels are deleted.

Unwanted spontaneous responsiveness and burst suppression in patients undergoing entropy-guided total intravenous anesthesia with target-controlled infusion: An observational prospective trial

Study objectiveTo estimate the incidence of unwanted spontaneous responsiveness and burst suppression (BSupp) in patients undergoing state entropy (SE) and surgical pleth index (SPI)-guided total intravenous anesthesia (TIVA) with target-controlled infusion (TCI). DesignObservational, prospective, single-center study. SettingsOperating room. Patients107 adult (<65 years) and elderly (≥65 years) women undergoing breast surgery. InterventionsPropofol-remifentanil TIVA-TCI-guided by SE for depth of anesthesia monitoring (target value 40–60) and SPI for antinociception monitoring (target value 20–50) without neuromuscular blockade. MeasurementsAge; body mass index; American Society of Anesthesiologists physical status classification; concentration at the effect site of propofol (CeP) and remifentanil (CeR) at loss of responsiveness (LoR), median during anesthesia maintenance (MdM), and at return of responsiveness (RoR); propofol infusion duration; incidence of postoperative delirium (POD) with Confusing Assessment Method for the Intensive Care Unit. Main resultsDuring SE-SPI-guided TIVA-TCI, 13.1% of patients showed unwanted spontaneous responsiveness, whereas 45.8% showed BSupp. Unwanted spontaneous responsiveness was observed mainly in adults (p < 0.05), and higher CeP RoR (p < 0.05) was registered. BSupp was observed mainly in patients showing a lower CeP MdM (p < 0.01) and CeP RoR (p < 0.05). Unwanted spontaneous responsiveness and BSupp were not associated with significant differences in CeRs. An age-related hysteresis effect was observed, resulting in higher CeP LoR than CeP RoR (p < 0.001). 12.2% of patients showed POD. Only preoperative serum albumin was associated with increased likelihood of POD (p = 0.046). ConclusionsThe SE-SPI-guided TIVA-TCI did not prevent unwanted spontaneous responsiveness and BSupp. CeP RoR may be used as a proxy for anesthetic sensitivity.

Claustrum modulates behavioral sensitivity and EEG activity of propofol anesthesia.

The claustrum has long been regarded as a vital center for conscious control. Electrical stimulation or damage to the claustrum can result in decreased awareness or loss of consciousness, suggesting that the claustrum may be a target for the action of general anesthetics. This study aimed to determine the role of the claustrum in propofol anesthesia. We first applied a fiber photometry calcium signal recording system to record the claustral neuronal activity during the entire process of propofol anesthesia. Chemogenetic activation of claustral neurones was then performed to verify their role in anesthesia. Finally, muscimol (GABAa receptor agonist) and gabazine (GABAa receptor antagonist) were microinjected into the claustrum to determine whether their GABAa receptors were involved in modulating propofol anesthesia. EEG and behavioral indicators, such as anesthetic sensitivity and efficacy, were recorded and analyzed. An evident anesthesia-related change in claustrum neuronal activity was suppressed during propofol-induced unconsciousness and restored following recovery from anesthesia. Chemogenetic activation of claustrum neuronsresults in attenuated propofol sensitivity, a shorter anesthesia duration, and an EEG shift toward wakefulness. Manipulation of GABAa receptors in the claustrum showed bidirectional control of propofol sensitivity, as activation decreases anesthesia efficiency while inactivation augments it. Additionally, inhibiting claustrum GABAa receptors increases cortical EEG slow waves. Claustrum neurones and their GABAa receptors are implicated in the modulation of propofol anesthesia in both behavioral and EEG assessments. Our findings create scope to reveal the brain targets of anesthetic action further and add to the existing evidence on the consciousness-modulating role of the claustrum.

An optimized mouse parabiosis protocol for investigation of aging and rejuvenative mechanisms.

Surgical parabiosis enables sharing of the circulating milieu between two organisms. This powerful model presents diverse complications based on age, strain, sex, and other experimental parameters. Here, we provide an optimized parabiosis protocol for the surgical union of two mice internally at the elbow and knee joints with continuous external joining of the skin. This protocol incorporates guidance and solutions to complications that can occur, particularly in aging studies, including non-cohesive pairing, variable anesthesia sensitivity, external and internal dehiscence, dehydration, and weight loss. We also offer a straightforward method for validating postoperative blood chimerism and confirming its time course using flow cytometry. Utilization of our optimized protocol can facilitate reproducible parabiosis experimentation to dynamically explore mechanisms of aging and rejuvenation.

Isoflurane inhibition of endocytosis is an anesthetic mechanism of action

The mechanisms of volatile anesthetic action remain among the most perplexing mysteries of medicine. Across phylogeny, volatile anesthetics selectively inhibit mitochondrial complex I, and they also depress presynaptic excitatory signaling. To explore how these effects are linked, we studied isoflurane effects on presynaptic vesicle cycling and ATP levels in hippocampal cultured neurons from wild-type and complex Imutant (Ndufs4(KO)) mice. To bypass complex I, we measured isoflurane effects on anesthetic sensitivity in mice expressing NADH dehydrogenase (NDi1). Endocytosis in physiologic concentrations of glucose was delayed by effective behavioral concentrations of isoflurane in both wild-type (τ [unexposed] 44.8± 24.2 s;τ [exposed] 116.1± 28.1 s; p<0.01) and Ndufs4(KO) cultures (τ [unexposed] 67.6± 16.0 s;τ [exposed] 128.4± 42.9 s; p= 0.028). Increasing glucose, to enhance glycolysis and increase ATP production, led to maintenance of both ATP levels and endocytosis (τ [unexposed] 28.0± 14.4;τ [exposed] 38.2± 5.7; reducing glucose worsened ATP levels and depressed endocytosis (τ [unexposed] 85.4± 69.3; τ [exposed]>1,000; p<0.001). The block in recycling occurred at the level of reuptake of synaptic vesicles into the presynaptic cell. Expression of NDi1 in wild-type mice caused behavioral resistance to isoflurane for tail clamp response (EC50 Ndi1(-) 1.27%± 0.14%; Ndi1(+) 1.55%± 0.13%) and halothane (EC50 Ndi1(-) 1.20%± 0.11%; Ndi1(+) 1.46%± 0.10%); expression of NDi1 in neurons improved hippocampal function, alleviated inhibition of presynaptic recycling, and increased ATP levels during isoflurane exposure. The clear alignment of cell culture data to invivo phenotypes of both isoflurane-sensitive and -resistant mice indicates that inhibition of mitochondrial complex I is a primary mechanism of action of volatile anesthetics.

Whole-exome sequencing reveals genetic variations in humans with differential sensitivity to sevoflurane：A prospective observational study

BackgroundThe anesthesia sensitivity is heterogeneous both in animals and humans, while the underlying molecular mechanism has not yet been determined. Here, for the first time, we conducted a prospective observational study to test whether genetic variations contribute to the differential sensitivity to sevoflurane in humans. MethodsFive hundred patients who underwent abdominal surgeries were included. The end-tidal sevoflurane concentration (ETsevo) was adjusted to maintain Bispectral index (BIS) value between 40 and 60. The mean ETsevo from 20 min after endotracheal intubation to 2 h after the beginning of surgery was calculated for each patient. These patients were further divided into high sensitivity group (mean - SD, H group) and low sensitivity group (mean + SD, L group) to investigate the genetic variants related to the differential sensitivity to sevoflurane by whole-exome sequencing (WES) and genome-wide association study (GWAS) in karyocyte from peripheral blood. ResultsThe mean ETsevo of these 500 patients was 1.60% ± 0.34%. After pairing, 55 patients from H group and 59 patients from L group were selected for WES (ETsevo of H group: 1.06% ± 0.13% vs. ETsevo of L group: 2.17% ± 0.16%, P < 0.001), respectively. Finally, FAT atypical cadherin 2 (FAT2, SNP rs174272, rs174271, and rs174261), acireductone dioxygenase 1 (ADI1, SNP rs117278), NEDD4 E3 ubiquitin protein ligase (NEDD4, SNP rs70048, rs70049, and rs70056), and FAD dependent oxidoreductase domain containing 2 (FOXRED2, SNP rs144281) were found to be associated with sevoflurane sensitivity. ConclusionsGenetic variations may contribute to the differential sensitivity to sevoflurane among humans.

Inactivation of Prefrontal Cortex Delays Emergence From Sevoflurane Anesthesia.

Studies aimed at investigating brain regions involved in arousal state control have been traditionally limited to subcortical structures. In the current study, we tested the hypothesis that inactivation of prefrontal cortex, but not two subregions within parietal cortex—somatosensory barrel field and medial/lateral parietal association cortex—would suppress arousal, as measured by an increase in anesthetic sensitivity. Male and female Sprague Dawley rats were surgically prepared for recording electroencephalogram and bilateral infusion into prefrontal cortex (N = 13), somatosensory barrel field (N = 10), or medial/lateral parietal association cortex (N = 9). After at least 10 days of post-surgical recovery, 156 μM tetrodotoxin or saline was microinjected into one of the cortical sites. Ninety minutes after injection, rats were anesthetized with 2.5% sevoflurane and the time to loss of righting reflex, a surrogate for loss of consciousness, was measured. Sevoflurane was stopped after 45 min and the time to return of righting reflex, a surrogate for return of consciousness, was measured. Tetrodotoxin-mediated inactivation of all three cortical sites decreased (p < 0.05) the time to loss of righting reflex. By contrast, only inactivation of prefrontal cortex, but not somatosensory barrel field or medial/lateral parietal association cortex, increased (p < 0.001) the time to return of righting reflex. Burst suppression ratio was not altered following inactivation of any of the cortical sites, suggesting that there was no global effect due to pharmacologic lesion. These findings demonstrate that prefrontal cortex plays a causal role in emergence from anesthesia and behavioral arousal.

This Month in Anesthesiology

This Month in Anesthesiology

Consciousness, Anesthesia, and Acetylcholine.

Consciousness, Anesthesia, and Acetylcholine.

Forebrain Acetylcholine Modulates Isoflurane and Ketamine Anesthesia in Adult Mice.

Cholinergic drugs are known to modulate general anesthesia, but anesthesia responses in acetylcholine-deficient mice have not been studied. It was hypothesized that mice with genetic deficiency of forebrain acetylcholine show increased anesthetic sensitivity to isoflurane and ketamine and decreased gamma-frequency brain activity. Male adult mice with heterozygous knockdown of vesicular acetylcholine transporter in the brain or homozygous knockout of the transporter in the basal forebrain were compared with wild-type mice. Hippocampal and frontal cortical electrographic activity and righting reflex were studied in response to isoflurane and ketamine doses. The loss-of-righting-reflex dose for isoflurane was lower in knockout (mean ± SD, 0.76 ± 0.08%, n = 18, P = 0.005) but not knockdown (0.78 ± 0.07%, n = 24, P = 0.021), as compared to wild-type mice (0.83 ± 0.07%, n = 23), using a significance criterion of P = 0.017 for three planned comparisons. Loss-of-righting-reflex dose for ketamine was lower in knockout (144 ± 39 mg/kg, n = 14, P = 0.006) but not knockdown (162 ± 32 mg/kg, n = 20, P = 0.602) as compared to wild-type mice (168 ± 24 mg/kg, n = 21). Hippocampal high-gamma (63 to 100 Hz) power after isoflurane was significantly lower in knockout and knockdown mice compared to wild-type mice (isoflurane-dose and mouse-group interaction effect, F[8,56] = 2.87, P = 0.010; n = 5 to 6 mice per group). Hippocampal high-gamma power after ketamine was significantly lower in both knockout and knockdown mice when compared to wild-type mice (interaction effect F[2,13] = 6.06, P = 0.014). The change in frontal cortical gamma power with isoflurane or ketamine was not statistically different among knockout, knockdown, and wild-type mice. These findings suggest that forebrain cholinergic neurons modulate behavioral sensitivity and hippocampal gamma activity during isoflurane and ketamine anesthesia.

Abstract 544: Increase in Isoflurane-mediated Blood-brain-barrier (bbb) Permeability is Regulated by Mmp3 via the Erk Signal Pathway

Introduction: The blood-brain barrier (BBB) normally maintains the CNS microenvironment. The effect of isoflurane, widely used in clinical anesthesia, on the BBB permeability has not been well studied. Matrix metalloproteinase 3 (MMP3) is implicated in the disruption of BBB. However, the direct role for MMP3 in regulating BBB and the underlying molecular mechanism has not yet been elucidated. We hypothesized that MMP3 plays a critical role in isoflurane mediated increase in BBB permeability. Methods: We used MMP3 deficient (MMP3 -/- ) mice and its littermate, wild-type (MMP3 +/+ ), as a control. Animals were assigned to either vehicle-air or isoflurane in 3 different groups: control, MMP3 -/- and control+MMP3 administration. We evaluated the anesthetic effect of isoflurane by the time of anesthesia induction, emergency time and volume of isoflurane. MMP3 levels were measured in different organs. We monitored the permeability of mouse BBB through in vivo (Evans blue dye extravasation, Sodium-FITC, and brain water content) and an in vitro model of BBB (Electrical cell impedance sensor assay and transwell permeability assay). To determine the mechanism of MMP3 on BBB permeability, we also used an ERK-inhibitor. Expression of the endothelial tight junctional protein was detected by both western blot and immunofluorescence staining. Results: The use of MMP3 increased the anesthetic sensitivity of isoflurane compared with the control group. In contrast, MMP3 KO mice displayed significantly longer induction time, higher isoflurane usage volume, and lower emergency time. Data showed that MMP3 increased BBB permeability in both in vivo and in vitro experiments, which is associated with a reduction in occluding, ZO-1 and claudin-5. We found mmp3 levels had negative correlations with tight junctional proteins and positive associations with p-ERK. Moreover, the use of an ERK-inhibitor abolished the effect of MMP3 on the junctional protein and in vitro BBB permeability. Conclusion: Our data suggest that MMP3 is required for modulation of isoflurane mediated BBB permeability by the reduction of tight junctional protein expression via the ERK pathway. Thus, mmp3 enhances the anesthetic effect of isoflurane, while the deletion of MMP3 protects against BBB disruption.