Acute Ketamine Impairs Mitochondrial Function and Promotes Superoxide Dismutase Activity in the Rat Brain

The impact of ketamine and thiopental anesthesia on ultraweak photon emission and oxidative-nitrosative stress in rat brains

Anesthetics such as ketamine and thiopental, commonly used for inducing unconsciousness, have distinct effects on neuronal activity, metabolism, and cardiovascular and respiratory systems. Ketamine increases heart rate and blood pressure while preserving respiratory function, whereas thiopental decreases both and can cause respiratory depression. This study investigates the impact of ketamine (100 mg/kg) and thiopental (45 mg/kg) on ultraweak photon emission (UPE), oxidative-nitrosative stress, and antioxidant capacity in isolated rat brains. To our knowledge, no previous study has investigated and compared UPE in the presence and absence of anesthesia. Here, we compare the effects of ketamine and thiopental anesthetics with each other and with a non-anesthetized control group. Ketamine increased UPE, lipid peroxidation, and antioxidant enzyme activity while reducing thiol levels. Conversely, thiopental decreased UPE, oxidative markers, and antioxidant enzyme activity, while increasing thiol levels. UPE was negatively correlated with thiol levels and positively correlated with oxidative stress markers. These findings suggest that the contrasting effects of ketamine and thiopental on UPE are linked to their differing impacts on brain oxidative stress and antioxidant capacity. This research suggests a potential method to monitor brain oxidative stress via UPE during anesthesia, and opens up new ways for understanding and managing anesthetic effects.

Effects of Anesthesia with Pentobarbital/Ketamine on Mitochondrial Permeability Transition Pore Opening and Ischemic Brain Damage

BACKGROUND AND OBJECTIVE

The alteration of mitochondrial functions, especially the opening of the mitochondrial permeability transition pore (mPTP), has been proposed as a key mechanism in the development of lesions in cerebral ischemia, wherefore it is considered as an important target for drugs against ischemic injury. In this study, we aimed to investigate the effects of mitochondrial complex I inhibitors as possible regulators of mPTP using an in vitro brain ischemia model of the pentobarbital/ketamine (PBK)-anesthetized rats.

RESULTS

We found that PBK anesthesia itself delayed Ca2+-induced mPTP opening and partially recovered the respiratory functions of mitochondria, isolated from rat brain cortex and cerebellum. In addition, PBK reduced cell death in rat brain slices of cerebral cortex and cerebellum. PBK inhibited the adenosine diphosphate (ADP)-stimulated respiration of isolated cortical and cerebellar mitochondria respiring with complex I-dependent substrates pyruvate and malate. Moreover, pentobarbital alone directly increased the resistance of isolated cortex mitochondria to Ca2+-induced activation of mPTP and inhibited complex I-dependent respiration and mitochondrial complex I activity. In contrast, ketamine had no direct effect on functions of isolated normal cortex and cerebellum mitochondria.

CONCLUSIONS

Altogether, this suggests that modulation of mitochondrial complex I activity by pentobarbital during PBK anesthesia may increase the resistance of mitochondria to mPTP opening, which is considered the key event in brain cell necrosis during ischemia.

Copper Chaperone Atox1 Protected the Cochlea From Cisplatin by Regulating the Copper Transport Family and Cell Cycle

Antioxidant 1 copper chaperone (Atox1) may contribute to preventing DDP cochlear damage by regulating copper transport family and cell cycle proteins. A rat model of cochlear damage was developed by placing gelatin sponges treated with DDP in the cochlea. HEI-OC1 cells were treated with 133 μM DDP as a cell model. DDP-induced ototoxicity in rats was confirmed by immunofluorescence (IF) imaging. The damage of DDP to HEI-OC1 cells was assessed by using CCK-8, TUNEL, and flow cytometry. The relationship between Atox1, a member of the copper transport protein family, and the damage to in vivo/vitro models was explored by qRT-PCR, western blot, CCK-8, TUNEL, and flow cytometry. DDP had toxic and other side effects causing cochlear damage and promoted HEI-OC1 cell apoptosis and cell cycle arrest. The over-expression of Atox1 (oe-Atox1) was accomplished by transfecting lentiviral vectors into in vitro/vivo models. We found that oe-Atox1 increased the levels of Atox1, copper transporter 1 (CTR1), and SOD3 in HEI-OC1 cells and decreased the expression levels of ATPase copper transporting α (ATP7A) and ATPase copper transporting β (ATP7B). In addition, the transfection of oe-Atox1 decreased cell apoptosis rate and the number of G2/M stage cells. Similarly, the expression of myosin VI and phalloidin of cochlea cells in vivo decreased. Atox1 ameliorated DDP-induced damage to HEI-OC1 cells or rats' cochlea by regulating the levels of members of the copper transport family.

Neuroprotective effects of dimethyl fumarate against manic-like behavior induced by ketamine in rats

Medications for treating bipolar disorder (BD) are limited and can cause side effects if used chronically. Therefore, efforts are being made to use new agents in the control and treatment of BD. Considering the antioxidant and anti-inflammatory effects of dimethyl fumarate (DMF), this study was performed to examine the role of DMF on ketamine (KET)-induced manic-like behavior (MLB) in rats. Forty-eight rats were randomly divided into eight groups, including three groups of healthy rats: normal, lithium chloride (LiCl) (45 mg/kg, p.o.), and DMF (60 mg/kg, p.o.), and five groups of MLB rats: control, LiCl, and DMF (15, 30, and 60 mg/kg, p.o.), which received KET at a dose of 25 mg/kg, i.p. The levels of total sulfhydryl groups (total SH), thiobarbituric acid reactive substances (TBARS), nitric oxide (NO), and tumor necrosis factor-alpha (TNF-α), as well as the activity of antioxidant enzymes including catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx) in the prefrontal cortex (PFC) and hippocampus (HPC), were measured. DMF prevented hyperlocomotion (HLM) induced by KET. It was found that DMF could inhibit the increase in the levels of TBARS, NO, and TNF-α in the HPC and PFC of the brain. Furthermore, by examining the amount of total SH and the activity of SOD, GPx, and CAT, it was found that DMF could prevent the reduction of the level of each of them in the brain HPC and PFC. DMF pretreatment improved the symptoms of the KET model of mania by reducing HLM, oxidative stress, and modulating inflammation.

Inhibition of mitochondrial respiration by general anesthetic drugs

General anesthetic drugs have been associated with various unwanted effects including an interference with mitochondrial function. We had previously observed increases of lactate formation in the mouse brain during anesthesia with volatile anesthetic agents. In the present work, we used mitochondria that were freshly isolated from mouse brain to test mitochondrial respiration and ATP synthesis in the presence of six common anesthetic drugs. The volatile anesthetics isoflurane, halothane, and (to a lesser extent) sevoflurane caused an inhibition of complex I of the electron transport chain in a dose-dependent manner. Significant effects were seen at concentrations that are reached under clinical conditions (< 0.5 mM). Pentobarbital and propofol also inhibited complex I but at concentrations that were two-fold higher than clinical EC50 values. Only propofol caused an inhibition of complex II. Complex IV respiration was not affected by either agent. Ketamine did not affect mitochondrial respiration. Similarly, all anesthetic agents except ketamine suppressed ATP production at high concentrations. Only halothane increased cytochrome c release indicating damage of the mitochondrial membrane. In summary, volatile general anesthetic agents as well as pentobarbital and propofol dose-dependently inhibit mitochondrial respiration. This action may contribute to depressive actions of the drugs in the brain.

A mini-review of the effects of inhalational and intravenous anesthetics on oxidative stress in dogs

General anesthesia increases the production of reactive oxygen species (ROS), which can exacerbate or increase oxidative stress and thus affect the prognosis of surgical procedures. Oxidative stress has been implicated in the development of cardiovascular, dermatologic, oncologic, and other diseases in dogs, as well as ischemia and reperfusion injury. Some anesthetics, such as halogenated anesthetics, have been shown to stimulate the production of ROS, while others, such as propofol, have antioxidant properties. However, the antioxidant effects of these anesthetics may not be sufficient to counteract oxidative damage at the doses used clinically. Nevertheless, the effects of anesthetics should be considered to minimize oxidative damage during anesthesia in dogs to improve the outcome of procedures requiring general anesthesia. This mini-review addresses the current knowledge on oxidative stress during inhalational and intravenous anesthesia in dogs. There is still a lack of information on the management of anesthesia in dogs with respect to oxidative stress. Further research, including comprehensive clinical studies is needed to better understand oxidative injury mechanisms and improve perioperative protocols during anesthesia in dogs.

Cardiac mitochondrial energetics of the Australasian red spiny lobster, Jasus edwardsii, when exposed to isoeugenol within the commercial anaesthetic AQUI-S

The anaesthetic isoeugenol has been used as metabolic suppressant for commercial transport of live lobsters in order to decrease energy expenditure aand improve survival. Given the central role of mitochondria in metabolism and structural similarities of isoeugenol to the mitochondrial electron carrier coenzyme Q, we explored the influence on mitochondrial function of isoeugenol. Mitochondrial function was measured using high resolution respirometry and saponin permeabilized heart fibres from the Australasian red spiny lobster, Jasus edwardsii. Relative to vehicle (polysorbate), isoeugenol inhibited respiration supported by complex I (CI) and cytochrome c oxidase (CCO). While complex II (CII), which also reduces coenzyme Q was largely unaffected by isoeugenol, respiration supported by CII when uncoupled was depressed. Titration of isoeugenol indicates that respiration through CI has a half inhibition constant (IC50) of 2.4±0.1 µM, and full inhibition constant IC100 of approximately 6.3 µM. These concentrations are consistent with those used for transport and euthanasia of J. edwardsii and indicates that CI is a possible target of isoeugenol like many other anaesthetics with quinone-like structures.

'Fit for surgery': The relationship between cardiorespiratory fitness and postoperative outcomes

New Findings

What is the topic of this review?

The relationships and physiological mechanisms underlying the clinical benefits of cardiorespiratory fitness (CRF) in patients undergoing major intra‐abdominal surgery.

What advances does it highlight?

Elevated CRF reduces postoperative morbidity/mortality, thus highlighting the importance of CRF as an independent risk factor. The vascular protection afforded by exercise prehabilitation can further improve surgical risk stratification and postoperative outcomes.

Abstract

Surgery accounts for 7.7% of all deaths globally and the number of procedures is increasing annually. A patient's ‘fitness for surgery’ describes the ability to tolerate a physiological insult, fundamental to risk assessment and care planning. We have evolved as obligate aerobes that rely on oxygen (O₂). Systemic O₂ consumption can be measured via cardiopulmonary exercise testing (CPET) providing objective metrics of cardiorespiratory fitness (CRF). Impaired CRF is an independent risk factor for mortality and morbidity. The perioperative period is associated with increased O₂ demand, which if not met leads to O₂ deficit, the magnitude and duration of which dictates organ failure and ultimately death. CRF is by far the greatest modifiable risk factor, and optimal exercise interventions are currently under investigation in patient prehabilitation programmes. However, current practice demonstrates potential for up to 60% of patients, who undergo preoperative CPET, to have their fitness incorrectly stratified. To optimise this work we must improve the detection of CRF and reduce potential for interpretive error that may misinform risk classification and subsequent patient care, better quantify risk by expressing the power of CRF to predict mortality and morbidity compared to traditional cardiovascular risk factors, and improve patient interventions with the capacity to further enhance vascular adaptation. Thus, a better understanding of CRF, used to determine fitness for surgery, will enable both clinicians and exercise physiologists to further refine patient care and management to improve survival.

Neonatal Anesthesia and Oxidative Stress

Neonatal anesthesia, while often essential for surgeries or imaging procedures, is accompanied by significant risks to redox balance in the brain due to the relatively weak antioxidant system in children. Oxidative stress is characterized by concentrations of reactive oxygen species (ROS) that are elevated beyond what can be accommodated by the antioxidant defense system. In neonatal anesthesia, this has been proposed to be a contributing factor to some of the negative consequences (e.g., learning deficits and behavioral abnormalities) that are associated with early anesthetic exposure. In order to assess the relationship between neonatal anesthesia and oxidative stress, we first review the mechanisms of action of common anesthetic agents, the key pathways that produce the majority of ROS, and the main antioxidants. We then explore the possible immediate, short-term, and long-term pathways of neonatal-anesthesia-induced oxidative stress. We review a large body of literature describing oxidative stress to be evident during and immediately following neonatal anesthesia. Moreover, our review suggests that the short-term pathway has a temporally limited effect on oxidative stress, while the long-term pathway can manifest years later due to the altered development of neurons and neurovascular interactions.

A New Strategy to Preserve and Assess Oxygen Consumption in Murine Tissues

Mitochondrial dysfunctions are implicated in several pathologies, such as metabolic, cardiovascular, respiratory, and neurological diseases, as well as in cancer and aging. These metabolic alterations are usually assessed in human or murine samples by mitochondrial respiratory chain enzymatic assays, by measuring the oxygen consumption of intact mitochondria isolated from tissues, or from cells obtained after physical or enzymatic disruption of the tissues. However, these methodologies do not maintain tissue multicellular organization and cell-cell interactions, known to influence mitochondrial metabolism. Here, we develop an optimal model to measure mitochondrial oxygen consumption in heart and lung tissue samples using the XF24 Extracellular Flux Analyzer (Seahorse) and discuss the advantages and limitations of this technological approach. Our results demonstrate that tissue organization, as well as mitochondrial ultrastructure and respiratory function, are preserved in heart and lung tissues freshly processed or after overnight conservation at 4 °C. Using this method, we confirmed the repeatedly reported obesity-associated mitochondrial dysfunction in the heart and extended it to the lungs. We set up and validated a new strategy to optimally assess mitochondrial function in murine tissues. As such, this method is of great potential interest for monitoring mitochondrial function in cohort samples.

MEGDEL Syndrome and Its Anesthetic Implications

MEGDEL syndrome gains its name for its following features: 3-methylglutaconic aciduria (MEG), deafness (D), encephalopathy (E), Leigh-like syndrome (L). This syndrome is caused by biallelic mutations in the serine active site-containing protein 1 (SERAC1 ) gene. When these patients present with hepatopathy (H) in addition to the above manifestations the syndrome is labeled as MEGD(H)EL. The pathology of the disease shares features with different types of inborn errors of metabolism. We present the anesthetic management of a neonate who was diagnosed with MEGD(H)EL syndrome and underwent diagnostic magnetic resonance imaging of the brain at 14 days of postnatal age. We describe the epidemiology and important features of this rare disease that are pertinent for the anesthesiologist.

Effect of neuropsychiatric medications on mitochondrial function: For better or for worse

Individuals with mitochondrial disease often present with psychopathological comorbidity, and mitochondrial dysfunction has been proposed as the underlying pathobiology in various psychiatric disorders. Several studies have suggested that medications used to treat neuropsychiatric disorders could directly influence mitochondrial function. This review provides a comprehensive overview of the effect of these medications on mitochondrial function. We collected preclinical information on six major groups of antidepressants and other neuropsychiatric medications and found that the majority of these medications either positively influenced mitochondrial function or showed mixed effects. Only amitriptyline, escitalopram, and haloperidol were identified as having exclusively adverse effects on mitochondrial function. In the absence of formal clinical trials, and until such trials are completed, the data from preclinical studies reported and discussed here could inform medication prescribing practices for individuals with psychopathology and impaired mitochondrial function in the underlying pathology.

A synthetic peptide rescues rat cortical neurons from anesthetic-induced cell death, perturbation of growth and synaptic assembly

Anesthetics are deemed necessary for all major surgical procedures. However, they have also been found to exert neurotoxic effects when tested on various experimental models, but the underlying mechanisms remain unknown. Earlier studies have implicated mitochondrial fragmentation as a potential target of anesthetic-induced toxicity, although clinical strategies to protect their structure and function remain sparse. Here, we sought to determine if preserving mitochondrial networks with a non-toxic, short-life synthetic peptide—P110, would protect cortical neurons against both inhalational and intravenous anesthetic-induced neurotoxicity. This study provides the first direct and comparative account of three key anesthetics (desflurane, propofol, and ketamine) when used under identical conditions, and demonstrates their impact on neonatal, rat cortical neuronal viability, neurite outgrowth and synaptic assembly. Furthermore, we discovered that inhibiting Fis1-mediated mitochondrial fission reverses anesthetic-induced aberrations in an agent-specific manner. This study underscores the importance of designing mitigation strategies invoking mitochondria-mediated protection from anesthetic-induced toxicity in both animals and humans.

Crocins, the Bioactive Components of Crocus sativus L., Counteract the Disrupting Effects of Anesthetic Ketamine on Memory in Rats

Consistent experimental evidence suggests that anesthetic doses of the non-competitive N-methyl-d-aspartate (NMDA) receptor antagonist ketamine cause severe memory impairments in rodents. Crocins are among the various bioactive ingredients of the plant Crocus sativus L., and their implication in memory is well-documented. It has not yet been elucidated if crocins are able to attenuate the memory deficits produced by anesthetic ketamine. The present study was undertaken aiming to clarify this issue in the rat. For this aim, the object recognition, the object location and the habituation tests, reflecting non-spatial recognition memory, spatial recognition memory and associative memory, respectively, were utilized. A post-training challenge with crocins (15–30 mg/kg, intraperitoneally (i.p.), acutely) counteracted anesthetic ketamine (100 mg/kg, i.p.)-induced performance impairments in all the above-mentioned behavioral memory paradigms. The current findings suggest that crocins modulate anesthetic ketamine’s amnestic effects.

Impact of experimental obesity on diaphragm structure, function, and bioenergetics

Obesity is associated with bioenergetic dysfunction of peripheral muscles; however, little is known regarding the impact of obesity on the diaphragm. We hypothesized that obesity would be associated with diaphragm dysfunction attributable to mitochondrial oxygen consumption and structural and ultrastructural changes. Wistar rat litters were culled to 3 pups to induce early postnatal overfeeding and consequent obesity. Control animals were obtained from unculled litters. From postnatal day 150, diaphragm ultrasound, computed tomography, high-resolution respirometry, immunohistochemical, biomolecular, and ultrastructural histological analyses were performed. The diaphragms of obese animals, compared with those of controls, presented changes in morphology as increased thickening fraction, diaphragm excursion, and diaphragm dome height, as well as increased mitochondrial respiratory capacity coupled to ATP synthesis and maximal respiratory capacity. Fatty acid synthase gene expression was also higher in obese animals, suggesting a source of energy for the respiratory chain. Myosin heavy chain-IIA was increased, indicating shift from glycolytic toward oxidative muscle fiber profile. Diaphragm tissue also exhibited ultrastructural changes, such as compact, round, and swollen mitochondria with fainter cristae and more lysosomal bodies. Dynamin-1 expression in the diaphragm was reduced in obese rats, suggesting decreased mitochondrial fission. Furthermore, gene expressions of peroxisome γ proliferator-activated receptor coactivator-1α and superoxide dismutase-2 were lower in obese animals than in controls, which may indicate a predisposition to oxidative injury. In conclusion, in the obesity model used herein, muscle fiber phenotype was altered in a manner likely associated with increased mitochondrial respiratory capability, suggesting respiratory adaptation to increased metabolic demand.NEW & NOTEWORTHY Obesity has been associated with peripheral muscle dysfunction; however, little is known about its impact on the diaphragm. In the current study, we found high oxygen consumption in diaphragm tissue and changes in muscle fiber phenotypes toward a more oxidative profile in experimental obesity.

Safety of drug use in patients with a primary mitochondrial disease: An international Delphi-based consensus

Clinical guidance is often sought when prescribing drugs for patients with primary mitochondrial disease. Theoretical considerations concerning drug safety in patients with mitochondrial disease may lead to unnecessary withholding of a drug in a situation of clinical need. The aim of this study was to develop consensus on safe medication use in patients with a primary mitochondrial disease. A panel of 16 experts in mitochondrial medicine, pharmacology, and basic science from six different countries was established. A modified Delphi technique was used to allow the panellists to consider draft recommendations anonymously in two Delphi rounds with predetermined levels of agreement. This process was supported by a review of the available literature and a consensus conference that included the panellists and representatives of patient advocacy groups. A high level of consensus was reached regarding the safety of all 46 reviewed drugs, with the knowledge that the risk of adverse events is influenced both by individual patient risk factors and choice of drug or drug class. This paper details the consensus guidelines of an expert panel and provides an important update of previously established guidelines in safe medication use in patients with primary mitochondrial disease. Specific drugs, drug groups, and clinical or genetic conditions are described separately as they require special attention. It is important to emphasise that consensus-based information is useful to provide guidance, but that decisions related to drug prescribing should always be tailored to the specific needs and risks of each individual patient. We aim to present what is current knowledge and plan to update this regularly both to include new drugs and to review those currently included.

A Metabolic Mechanism for Anaesthetic Suppression of Cortical Synaptic Function in Mouse Brain Slices-A Pilot Investigation

Regulation of synaptically located ionotropic receptors is thought to be the main mechanism by which anaesthetics cause unconsciousness. An alternative explanation, which has received much less attention, is that of primary anaesthetic disruption of brain metabolism via suppression of mitochondrial proteins. In this pilot study in mouse cortical slices, we investigated the effect of disrupting cellular metabolism on tissue oxygen handling and cortical population seizure-like event (SLE) activity, using the mitochondrial complex I inhibitor rotenone, and compared this to the effects of the general anaesthetics sevoflurane, propofol and ketamine. Rotenone caused an increase in tissue oxygen (98 mmHg to 157 mmHg (p < 0.01)) before any measurable change in SLE activity. Thereafter, tissue oxygen continued to increase and was accompanied by a significant and prolonged reduction in SLE root mean square (RMS) activity (baseline RMS of 1.7 to 0.7 µV, p < 0.001) and SLE frequency (baseline 4.2 to 0.4 events/min, p = 0.001). This temporal sequence of effects was replicated by all three anaesthetic drugs. In conclusion, anaesthetics with differing synaptic receptor mechanisms all effect changes in tissue oxygen handling and cortical network activity, consistent with a common inhibitory effect on mitochondrial function. The temporal sequence suggests that the observed synaptic depression—as seen in anaesthesia—may be secondary to a reduction in cellular metabolic capacity.

Ketamine treatment affects hippocampal but not cortical mitochondrial function in prepubertal rats

Previous reports have shown that ketamine triggered apoptosis in immature developing brain involving mitochondrial-mediated pathways. However, no data for ketamine effects on hippocampal and cortical mitochondrial function are available in prepubertal rats. Twenty-one-day-old Sprague-Dawley rats received ketamine (40 mg/kg i.p.) for 3 days and were killed 24 hr after the last injection. Hippocampal mitochondria from ketamine-treated rats showed decreased malate-glutamate state 4 and 3 respiratory rates and an inhibition in complex I and IV activities. Hippocampal mitochondrial membrane depolarization and mitochondrial permeability transition induction were observed. This was not reflected in an increment of H₂ O₂ production probably due to increased Mn-SOD and catalase activities, 24 hr after treatment. Interestingly, increased H₂ O₂ production rates and cardiolipin oxidation were found in hippocampal mitochondria shortly after ketamine treatment (45 min). Unlike the hippocampus, ketamine did not affect mitochondrial parameters in the brain cortex, being the area less vulnerable to suffer ketamine-induced oxidative damage. Results provide evidences that exposure of prepubertal rats to ketamine leads to an induction of mitochondrial ROS generation at early stages of treatment that was normalized by the triggering of antioxidant systems. Although hippocampal mitochondria from prepubertal rats were capable of responding to the oxidative stress, they remain partially dysfunctional.

Energization by multiple substrates and calcium challenge reveal dysfunctions in brain mitochondria in a model related to acute psychosis

Schizophrenia etiology is unknown, nevertheless imbalances occurring in an acute psychotic episode are important to its development, such as alterations in cellular energetic state, REDOX homeostasis and intracellular Ca²⁺ management, all of which are controlled primarily by mitochondria. However, mitochondrial function was always evaluated singularly, in the presence of specific respiratory substrates, without considering the plurality of the electron transport system. In this study, mitochondrial function was analyzed under conditions of isolated or multiple respiratory substrates using brain mitochondria isolated from MK-801-exposed mice. Results showed a high H₂O₂ production in the presence of pyruvate/malate, with no change in oxygen consumption. In the condition of multiple substrates, however, this effect is lost. The analysis of Ca²⁺ retention capacity revealed a significant change in the uptake kinetics of this ion by mitochondria in MK-801-exposed animals. Futhermore, when mitochondria were exposed to calcium, a total loss of oxidative phosphorylation and an impressive increase in H₂O₂ production were observed in the condition of multiple substrates. There was no alteration in the activity of the antioxidant enzymes analyzed. The data demonstrate for the first time, in an animal model of psychosis, two important aspects (1) mitochondria may compensate deficiencies in a single mitochondrial complex when they oxidize several substrates simultaneously, (2) Ca²⁺ handling is compromised in MK-801-exposed mice, resulting in a loss of phosphorylative capacity and an increase in H₂O₂ production. These data favor the hypothesis that disruption of key physiological roles of mitochondria may be a trigger in acute psychosis and, consequently, schizophrenia.

Sub-anesthetic and anesthetic ketamine produce different long-lasting behavioral phenotypes (24 h post-treatment) via inducing different brain-derived neurotrophic factor (BDNF) expression level in the hippocampus

Clinical and preclinical researches have shown that sub-anesthetic ketamine elicits sustained antidepressant effects for up to 1-2 weeks. Pharmacokinetics studies (t1/2 = 23 min) in mice showed no ketamine residue at 24 h after sub-anesthetic or anesthetic ketamine administration. Therefore, this study aims to reveal the mechanism underlying these different biological functions at 24 h after sub-anesthetic and anesthetic ketamine treatment. First, at the animal behavioral level, we found that sub-anesthetic ketamine induced antidepressant and anxiolytic effects while anesthetic ketamine induced depressive-like phenotypes and cognitive impairment. Second, we examined the correlation between behavior phenotype and protein expression, and found that the Brain-derived neurotrophic factor (BDNF) level is oppositely regulated by sub-anesthetic and anesthetic ketamine. Sub-anesthetic ketamine significantly increased the BDNF level, correlating to antidepressant effects; whereas anesthetic dose reduced BDNF expression in the hippocampus, correlating to depressive-like behaviors, anxiety-like behaviors and cognitive impairment. Third, the antidepressant effects of sub-anesthetic ketamine were prevented by pre-treatment of ANA-12, a Tropomyosin receptor kinase B (TrkB) inhibitor. Thus, we conclude that BDNF may be the key factor underlying antidepressant and anxiolytic effects of sub-anesthetic ketamine at 24 h after treatment. These results may shed light on future studies and the development of long-lasting anti-depressant drugs and therapies.

Perioperative Oxidative Stress: The Unseen Enemy

Reactive oxygen species (ROS) are essential for cellular signaling and physiological function. An imbalance between ROS production and antioxidant protection results in a state of oxidative stress (OS), which is associated with perturbations in reduction/oxidation (redox) regulation, cellular dysfunction, organ failure, and disease. The pathophysiology of OS is closely interlinked with inflammation, mitochondrial dysfunction, and, in the case of surgery, ischemia/reperfusion injury (IRI). Perioperative OS is a complex response that involves patient, surgical, and anesthetic factors. The magnitude of tissue injury inflicted by the surgery affects the degree of OS, and both duration and nature of the anesthetic procedure applied can modify this. Moreover, the interindividual susceptibility to the impact of OS is likely to be highly variable and potentially linked to underlying comorbidities. The pathological link between OS and postoperative complications remains unclear, in part due to the complexities of measuring ROS- and OS-mediated damage. Exogenous antioxidant use and exercise have been shown to modulate OS and may have potential as countermeasures to improve postoperative recovery. A better understanding of the underlying mechanisms of OS, redox signaling, and regulation can provide an opportunity for patient-specific phenotyping and development of targeted interventions to reduce the disruption that surgery can cause to our physiology. Anesthesiologists are in a unique position to deliver countermeasures to OS and improve physiological resilience. To shy away from a process so fundamental to the welfare of these patients would be foolhardy and negligent, thus calling for an improved understanding of this complex facet of human biology.

Psychotropic and neurological medication effects on mitochondrial complex I and IV in rodent models

Mitochondrial complex I (NADH-dehydrogenase) and complex IV (cytochrome-c-oxidase) are reported to be affected by drugs used to treat psychiatric or neurodegenerative diseases, including antidepressants, antipsychotics, anxiolytics, mood stabilizers, stimulants, antidementia, and antiparkinsonian drugs. We conducted meta-analyses examining the effects of each drug category on complex I and IV. The electronic databases Pubmed, EMBASE, CENTRAL, and Google Scholar were searched for studies published between 1970 and 2018. Of 3105 screened studies, 68 articles covering 53 drugs were included in the meta-analyses. All studies assessed complex I and IV in rodent brain at the level of enzyme activity. Results revealed that selected antidepressants increase or decrease complex I and IV, antipsychotics and stimulants decrease complex I but increase complex IV, whereas anxiolytics, mood stabilizers, antidementia, and antiparkinsonian drugs preserve or even enhance both complex I and IV. Potential contributions to the drug effects were found to be related to the drugs' neurotransmitter receptor profiles with adrenergic (α1B), dopaminergic (D1/2), glutaminergic (NMDA1,3), histaminergic (H1), muscarinic (M1,3), opioid (OP1-3), serotonergic (5-HT_2A, 5-HT_2C, 5-HT_3A) and sigma (σ1) receptors having the greatest effects. The findings are discussed in relation to pharmacological mechanisms of action that might have relevance for clinical and research applications.

Cerebrovascular function and mitochondrial bioenergetics after ischemia-reperfusion in male rats

The underlying factors promoting increased mitochondrial proteins, mtDNA, and dilation to mitochondrial-specific agents in male rats following tMCAO are not fully elucidated. Our goal was to determine the morphological and functional effects of ischemia/reperfusion (I/R) on mitochondria using electron microscopy, Western blot, mitochondrial oxygen consumption rate (OCR), and Ca2+ sparks activity measurements in middle cerebral arteries (MCAs) from male Sprague Dawley rats (Naïve, tMCAO, Sham). We found a greatly increased OCR in ipsilateral MCAs (IPSI) compared with contralateral (CONTRA), Sham, and Naïve MCAs. Consistent with our earlier findings, the expression of Mitofusin-2 and OPA-1 was significantly decreased in IPSI arteries compared with Sham and Naïve. Mitochondrial morphology was disrupted in vascular smooth muscle, but morphology with normal and perhaps greater numbers of mitochondria were observed in IPSI compared with CONTRA MCAs. Consistently, there were significantly fewer baseline Ca2+ events in IPSI MCAs compared with CONTRA, Sham, and Naïve. Mitochondrial depolarization significantly increased Ca2+ sparks activity in the IPSI, Sham, Naïve, but not in the CONTRA group. Our data indicate that altered mitochondrial structure and function occur in MCAs exposed to I/R and that these changes impact not only OCR but Ca2+ sparks activity in both IPSI and CONTRA MCAs.

Ketamine-induced attenuation of reactive oxygen species in zebrafish is prevented by acetyl l-carnitine in vivo

Ketamine, an anesthetic, is a non-competitive antagonist of the calcium-permeable N-methyl-d-aspartate (NMDA) receptor. High concentrations of ketamine have been implicated in cardiotoxicity and neurotoxicity. Often, these toxicities are thought to be mediated by reactive oxygen species (ROS). However, findings to the contrary showing ketamine reducing ROS in mammalian cells and neurons in vitro, are emerging. Here, we determined the effects of ketamine on ROS levels in zebrafish larvae in vivo. Based on our earlier studies demonstrating reduction in ATP levels by ketamine, we hypothesized that as a calcium antagonist, ketamine would also prevent ROS generation, which is a by-product of ATP synthesis. To confirm that the detected ROS in a whole organism, such as the zebrafish larva, is specific, we used diphenyleneiodonium (DPI) that blocks ROS production by inhibiting the NADPH Oxidases (NOX). Upon 20 h exposure, DPI (5 and 10 μM) and ketamine at (1 and 2 mM) reduced ROS in the zebrafish larvae in vivo. Using acetyl l-carnitine (ALCAR), a dietary supplement, that induces mitochondrial ATP synthesis, we show elevated ROS generation with increasing ALCAR concentrations. Combined, ketamine and ALCAR counter-balanced ROS generation in the larvae suggesting that ketamine and ALCAR have opposing effects on mitochondrial metabolism, which may be key to maintaining ROS homeostasis in the larvae and affords ALCAR the ability to prevent ketamine toxicity. These results for the first time show ketamine's antioxidative and ALCAR's prooxidative effects in a live vertebrate.

Combined actions of blueberry extract and lithium on neurochemical changes observed in an experimental model of mania: exploiting possible synergistic effects

Bipolar disorder is a psychiatric disease characterized by recurrent episodes of mania and depression. Blueberries contain bioactive compounds with important pharmacological effects such as neuroprotective and antioxidant actions. The aim of this study was to investigate the effects of blueberry extract and/or lithium on oxidative stress, and acetylcholinesterase (AChE) and Na⁺, K⁺-ATPase activity in an experimental ketamine-induced model of mania. Male Wistar rats were pretreated with vehicle, blueberry extract (200 mg/kg), and/or lithium (45 mg/kg or 22.5 mg/kg twice daily) for 14 days. Between the 8th and 14th days, the animals also received an injection of ketamine (25 mg/kg) or vehicle. On the 15th day the animals received a single injection of ketamine; after 30 min, the locomotor activity was evaluated in an open field test. Ketamine administration induced an increase in locomotor activity. In the cerebral cortex, hippocampus and striatum, ketamine also induced an increase in reactive oxygen species, lipid peroxidation and nitrite levels, as well a decrease in antioxidant enzyme activity. Pretreatment with blueberry extract or lithium was able to prevent this change. Ketamine increased the AChE and Na⁺, K⁺-ATPase activity in brain structures, while the blueberry extract partially prevented these alterations. In addition, our results showed that the neuroprotective effect was not potentiated when lithium and blueberry extract treatment were given together. In conclusion, our findings suggest that blueberry extract has a neuroprotective effect against an experimental model of mania. However, more studies should be performed to evaluate its effects as an adjuvant therapy.

Effects of Anesthetic Ketamine on Anxiety-Like Behaviour in Rats

There is scarce information regarding the effects of anesthetic doses of the non-competitive N-methyl-D-aspartate receptor antagonist ketamine on anxiety. The current study evaluated the acute effects of intraperitoneally (i.p.) administered anesthetic ketamine (100 mg/kg) i.p. on anxiety in rats. For this purpose, the light/dark and the open field tests were utilized. The effects of anesthetic ketamine on motility were also examined using a motility cage. In the light/dark test, anesthetic ketamine, administered 24 h before testing reduced the number of transitions between the light and dark compartments and the time spent in the light compartment in the rats compared with their control cohorts. In addition, ketamine was found to exert a depressive effect on rats' motility. In the open field test, animals treated with anesthetic ketamine 24 h before testing spent essentially no time in the central area of the apparatus, decreased horizontal ambulatory activity, and preserved to a certain extent their exploratory behaviour compared to their control counterparts. The results suggest that, in spite of its hypokinetic effect, a single anesthetic ketamine administration apparently induces an anxiety-like state, while largely preserving exploratory behaviour in the rat. These effects were time-dependent they since they were extinguished when testing was carried out 48 h after anesthetic ketamine administration.

Regulation of cytochrome P450 gene expression by ketamine: a review

INTRODUCTION

Although used as an anesthetic drug for decades, ketamine appears to have garnered renewed interest due to its potential therapeutic uses in pain therapy, neurology, and psychiatry. Ketamine undergoes extensive oxidative metabolism by cytochrome P450 (CYP) enzymes. Considerable efforts have been expended to elucidate the ketamine-induced regulation of CYP gene expression. The safety profile of chronic ketamine administration is still unclear. Understanding how ketamine regulates CYP gene expression is clinically meaningful. Areas covered: In this article, the authors provide a brief review of clinical applications of ketamine and its metabolism by CYP enzymes. We discuss the effects of ketamine on the regulation of CYP gene expression, exploring aspects of cytoskeletal remodeling, mitochondrial functions, and calcium homeostasis. Expert opinion: Ketamine may inhibit CYP gene expression through inhibiting calcium signaling, decreasing ATP levels, producing excessive reactive oxygen species, and subsequently perturbing cytoskeletal dynamics. Further research is still needed to avoid possible ketamine-drug interactions during long-term use in the clinic.

Ketamine induction of p53-dependent apoptosis and oxidative stress in zebrafish (Danio rerio) embryos

Ketamine is a widely used pharmaceutical that has been detected in water sources worldwide. Zebrafish embryos were used in this study to investigate the oxidative stress and apoptotic signals following a 24h exposure to different ketamine concentrations (0, 50, 70 and 90 mg L^-1). Early blastula embryos (∼2 h post fertilisation-hpf) were exposed for 24 h and analysed at 8 and 26 hpf. Reactive oxygen species and apoptotic cells were identified in vivo, at 26 hpf. Enzymatic activities (superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), lactate dehydrogenase (LDH) and acetylcholinesterase (AChE)), glutathione levels (oxidised (GSSG) and reduced (GSH)), oxidative damage (lipid peroxidation (LPO) and protein carbonyls (CO)) as well as oxidative stress (gclc, gstp1, sod1 and cat), apoptosis (casp3a, casp6, casp8, casp9, aifm1 and tp53) and cell proliferation (pcna) related-genes were evaluated at 8 and 26 hpf. Caspase (3 and 9) activity was also determined at both time-points by colorimetric methods. Superoxide dismutase (SOD), catalase (CAT), glutathione levels (GSSG), caspase-9 and reactive oxygen species (ROS) were shown to be affected by ketamine exposure while in vivo analysis showed no difference in ROS. A significant up-regulation of superoxide dismutase (sod1) and catalase (cat) genes expression was also perceived. Ketamine-induced apoptosis was observed in vivo and confirmed by the apoptotic-related genes up-regulation. The overall results suggest that ketamine induced oxidative stress and apoptosis through the involvement of p53-dependent pathways in zebrafish embryos which could be important for the evaluation of the overall risk of ketamine in aquatic environments.

Magnetic Resonance Spectroscopy in Schizophrenia: Evidence for Glutamatergic Dysfunction and Impaired Energy Metabolism

In the past couple of decades, major efforts were made to increase reliability of metabolic assessments by magnetic resonance methods. Magnetic resonance spectroscopy (MRS) has been valuable for providing in vivo evidence and investigating biomarkers in neuropsychiatric disorders, namely schizophrenia. Alterations of glutamate and glutamine levels in brains of schizophrenia patients relative to healthy subjects are generally interpreted as markers of glutamatergic dysfunction. However, only a small fraction of MRS-detectable glutamate is involved in neurotransmission. Here we review and discuss brain metabolic processes that involve glutamate and that are likely to be implicated in neuropsychiatric disorders.

Mechanistic studies on ketamine-induced mitochondrial toxicity in zebrafish embryos

Ketamine, a phencyclidine derivative, is an antagonist of the Ca²⁺-permeable N-methyl-d-aspartate (NMDA)-type glutamate receptors. It is a pediatric anesthetic and has been implicated in developmental neurotoxicity. Ketamine has also been shown to deplete ATP in mammalian cells. Our previous studies showed that acetyl l-carnitine (ALCAR) prevented ketamine-induced cardiotoxicity and neurotoxicity in zebrafish embryos. Based on our finding that ALCAR's protective effect was blunted by oligomycin A, an inhibitor of ATP synthase, we further investigated the effects of ketamine and ALCAR on ATP levels, mitochondria and ATP synthase in zebrafish embryos. The results demonstrated that ketamine reduced ATP levels in the embryos but not in the presence of ALCAR. Ketamine reduced total mitochondrial protein levels and mitochondrial potential, which were prevented with ALCAR co-treatment. To determine the cause of ketamine-induced ATP deficiency, we explored the status of ATP synthase. The results showed that a subunit of ATP synthase, atp5α1, was transcriptionally down-regulated by ketamine, but not in the presence of ALCAR, although ketamine caused a significant upregulation in another ATP synthase subunit, atp5β and total ATP synthase protein levels. Most of the ATP generated by heart mitochondria are utilized for its contraction and relaxation. Ketamine-treated embryos showed abnormal heart structure, which was abolished with ALCAR co-treatment. This study offers evidence for a potential mechanism by which ketamine could cause ATP deficiency mediated by mitochondrial dysfunction.

Anesthetic Management of a Child With Unspecified Mitochondrial Disease in an Outpatient Dental Setting

Mitochondrial disease (MD) represents a category of metabolic disorders with a wide range of symptoms across a variety of organ systems. It occurs with an incidence of greater than 1:5000 and can be difficult to specifically diagnose because of the variety of clinical presentations and multiple genomic origins. Although phenotypically variable, MD symptoms often include hypotonia, cardiac defects, dysautonomia, and metabolic dysfunction. Mitochondrial disease presents a unique challenge in terms of anesthetic management, as many anesthetic drugs suppress mitochondrial function. Additional considerations may need to be made in order to evaluate the patient's metabolic compensation prior to surgery. This article presents an in-depth discussion of a case involving a nearly 10-year-old boy with a history of an unspecified form of MD, who presented for endodontic treatment of tooth No. 30 under deep sedation. The article also provides a thorough review of the current literature surrounding the anesthetic management of patients with MD.

Preventive effects of blueberry extract on behavioral and biochemical dysfunctions in rats submitted to a model of manic behavior induced by ketamine

The aim of the present study was to evaluate the protective effects of blueberry extract on oxidative stress and inflammatory parameters in a model of mania induced by ketamine administration in rats. Male rats were pretreated with blueberry extract (200mg/kg, once a day for 14days), lithium chloride (45mg/kg, mood stabilizer used as a positive control, twice a day for 14days), or vehicle. Between the 8th and 14th days, rats also received an injection of ketamine (25mg/kg) or vehicle. In the 15th day, thirty minutes after ketamine administration the hyperlocomotion of the animals was assessed in the open - field apparatus. Immediately after the behavioral analysis brain and blood were collected for biochemical determinations. ketamine treatment induced hyperlocomotion and oxidative damage in cerebral cortex, hippocampus and striatum such as an increase in lipid peroxidation and a decrease in the antioxidant enzymes activities (superoxide dismutase, catalase e glutatione peroxidase). Ketamine administration also increased the IL-6 levels in serum in rats. Pretreatment of rats with blueberry extract or lithium prevented the hyperlocomotion, pro - oxidant effects and inflammation induced by ketamine. Our findings suggest that blueberry consumption has a neuroprotective potential against behavioral and biochemical dysfunctions induced in a preclinical model that mimic some aspects of the manic behavior.

Pharmacological and toxicological assessment of innovative self-assembled polymeric micelles as powders for insulin pulmonary delivery

Aim: Explore the use of polymeric micelles in the development of powders intended for pulmonary delivery of biopharmaceuticals, using insulin as a model protein. Materials & methods: Formulations were assessed in vitro for aerosolization properties and in vivo for efficacy and safety using a streptozotocin-induced diabetic rat model. Results: Powders presented good aerosolization properties like fine particle fraction superior to 40% and a mass median aerodynamic diameter inferior of 6 μm. Endotracheally instilled powders have shown a faster onset of action than subcutaneous administration of insulin at a dose of 10 IU/kg, with pharmacological availabilities up to 32.5% of those achieved by subcutaneous route. Additionally, micelles improved the hypoglycemic effect of insulin. Bronchoalveolar lavage screening for toxicity markers (e.g., lactate dehydrogenase, cytokines) revealed no signs of lung inflammation and cytotoxicity 14 days postadministration. Conclusion: Developed powders showed promising safety and efficacy characteristics for the systemic delivery of insulin by pulmonary administration.

Linking Mitochondria to Synapses: New Insights for Stress-Related Neuropsychiatric Disorders

The brain evolved cellular mechanisms for adapting synaptic function to energy supply. This is particularly evident when homeostasis is challenged by stress. Signaling loops between the mitochondria and synapses scale neuronal connectivity with bioenergetics capacity. A biphasic “inverted U shape” response to the stress hormone glucocorticoids is demonstrated in mitochondria and at synapses, modulating neural plasticity and physiological responses. Low dose enhances neurotransmission, synaptic growth, mitochondrial functions, learning, and memory whereas chronic, higher doses produce inhibition of these functions. The range of physiological effects by stress and glucocorticoid depends on the dose, duration, and context at exposure. These criteria are met by neuronal activity and the circadian, stress-sensitive and ultradian, stress-insensitive modes of glucocorticoid secretion. A major hallmark of stress-related neuropsychiatric disorders is the disrupted glucocorticoid rhythms and tissue resistance to signaling with the glucocorticoid receptor (GR). GR resistance could result from the loss of context-dependent glucocorticoid signaling mediated by the downregulation of the activity-dependent neurotrophin BDNF. The coincidence of BDNF and GR signaling changes glucocorticoid signaling output with consequences on mitochondrial respiration efficiency, synaptic plasticity, and adaptive trajectories.

Molecular substrates of schizophrenia: homeostatic signaling to connectivity

Schizophrenia (SZ) is a devastating psychiatric condition affecting numerous brain systems. Recent studies have identified genetic factors that confer an increased risk of SZ and participate in the disease etiopathogenesis. In parallel to such bottom-up approaches, other studies have extensively reported biological changes in patients by brain imaging, neurochemical and pharmacological approaches. This review highlights the molecular substrates identified through studies with SZ patients, namely those using top-down approaches, while also referring to the fruitful outcomes of recent genetic studies. We have subclassified the molecular substrates by system, focusing on elements of neurotransmission, targets in white matter-associated connectivity, immune/inflammatory and oxidative stress-related substrates, and molecules in endocrine and metabolic cascades. We further touch on cross-talk among these systems and comment on the utility of animal models in charting the developmental progression and interaction of these substrates. Based on this comprehensive information, we propose a framework for SZ research based on the hypothesis of an imbalance in homeostatic signaling from immune/inflammatory, oxidative stress, endocrine and metabolic cascades that, at least in part, underlies deficits in neural connectivity relevant to SZ. Thus, this review aims to provide information that is translationally useful and complementary to pathogenic hypotheses that have emerged from genetic studies. Based on such advances in SZ research, it is highly expected that we will discover biomarkers that may help in the early intervention, diagnosis or treatment of SZ.

Ketamine-induced oxidative stress at different developmental stages of zebrafish (Danio rerio) embryos

The changes induced by ketamine exposure were developmental stage-dependent, and related with the gradual development of the antioxidant defense system of the embryo, which is dependent on changes in energy-sensing pathways.

Region-specific effects of repeated ketamine administration on the presynaptic GABAergic neurochemistry in rat brain

A growing body of evidence indicates that clinical use of ketamine as a promising antidepressant can be accompanied by psychotic-like side effects. Although, the generation of such effects is thought to be attributed to dysfunction of prefrontal GABAergic interneurons, the mechanism underlying ketamine's propsychotic-like action is not fully understood. Due to wide spectrum of behavioral abnormalities, it is hypothesized that ketamine action is not limited to only cortical GABA metabolism but may also involve alterations in other functional brain areas. To test it, we treated rats with ketamine (30 mg/kg, i.p.) for 5 days, and next we analyzed GABA metabolizing enzymes in cortex, cerebellum, hippocampus and striatum. Our results demonstrated that diminished GAD67 expression in cortex, cerebellum (by ∼60%) and in hippocampus (by ∼40%) correlated with lowered protein level in these areas. The expression of GAD65 isoform decreased by ∼45% in striatum, but pronounced increase by ∼90% was observed in hippocampus. Consecutively, reduction in glutamate decarboxylase activity and GABA concentration were detected in cortex, cerebellum and striatum, but not in hippocampus. Ketamine administration decreased GABA transaminase protein in cortex and striatum (by ∼50% and 30%, respectively), which was reflected in diminished activity of the enzyme. Also, a significant drop in succinic semialdehyde dehydrogenase activity in cortex, cerebellum and striatum was present. These data suggest a reduced utilization of GABA for energetic purposes. In addition, we observed synaptic GABA release to be reduced by ∼30% from striatal terminals. It correlated with lowered KCl-induced Ca(2+) influx and decreased amount of L-type voltage-dependent calcium channel. Our results indicate that unique changes in GABA metabolism triggered by chronic ketamine treatment in functionally distinct brain regions may be involved in propsychotic-like effects of this drug.

Ketamine causes mitochondrial dysfunction in human induced pluripotent stem cell-derived neurons

Purpose

Ketamine toxicity has been demonstrated in nonhuman mammalian neurons. To study the toxic effect of ketamine on human neurons, an experimental model of cultured neurons from human induced pluripotent stem cells (iPSCs) was examined, and the mechanism of its toxicity was investigated.

Methods

Human iPSC-derived dopaminergic neurons were treated with 0, 20, 100 or 500 μM ketamine for 6 and 24 h. Ketamine toxicity was evaluated by quantification of caspase 3/7 activity, reactive oxygen species (ROS) production, mitochondrial membrane potential, ATP concentration, neurotransmitter reuptake activity and NADH/NAD⁺ ratio. Mitochondrial morphological change was analyzed by transmission electron microscopy and confocal microscopy.

Results

Twenty-four-hour exposure of iPSC-derived neurons to 500 μM ketamine resulted in a 40% increase in caspase 3/7 activity (P < 0.01), 14% increase in ROS production (P < 0.01), and 81% reduction in mitochondrial membrane potential (P < 0.01), compared with untreated cells. Lower concentration of ketamine (100 μM) decreased the ATP level (22%, P < 0.01) and increased the NADH/NAD⁺ ratio (46%, P < 0.05) without caspase activation. Transmission electron microscopy showed enhanced mitochondrial fission and autophagocytosis at the 100 μM ketamine concentration, which suggests that mitochondrial dysfunction preceded ROS generation and caspase activation.

Conclusions

We established an in vitro model for assessing the neurotoxicity of ketamine in iPSC-derived neurons. The present data indicate that the initial mitochondrial dysfunction and autophagy may be related to its inhibitory effect on the mitochondrial electron transport system, which underlies ketamine-induced neural toxicity. Higher ketamine concentration can induce ROS generation and apoptosis in human neurons.