Effect of Ketamine on Dendritic Arbor Development and Survival of Immature GABAergic Neurons In Vitro

Posterior hypothalamic theta rhythm: Electrophysiological basis and involvement of glutamatergic receptors

The posterior hypothalamic area (PHa), including the supramammillary nucleus (SuM) and posterior hypothalamic nuclei, forms a crucial part of the ascending brainstem hippocampal synchronizing pathway, that is involved in the frequency programming and modulation of rhythmic theta activity generated in limbic structures. Recent investigations show that in addition to being a modulator of limbic theta activity, the PHa is capable of producing well-synchronized local theta field potentials by itself. The purpose of this study was to examine the ability of the PHa to generate theta field potentials and accompanying cell discharges in response to glutamatergic stimulation under both in vitro and in vivo conditions. The second objective was to examine the electrophysiological properties of neurons located in the SuM and posterior hypothalamic nuclei. Extracellular in vivo and in vitro as well as intracellular in vitro experiments revealed that glutamatergic stimulation of PHa with kainic acid induces well-synchronized local theta field oscillations in both the supramammillary and posterior hypothalamic nuclei. Furthermore, the glutamatergic PHa theta rhythm recorded extracellularly was accompanied by the activity of specific subtypes of theta-related neurons. We identify, for the first time, a subpopulation of supramammillary and posterior hypothalamic neurons that express clear subthreshold membrane potential oscillations in the theta frequency range.

Changes in synaptic markers after administration of ketamine or psychedelics: a systematic scoping review

Background

Ketamine and psychedelics have abuse liability. They can also induce "transformative experiences" where individuals experience enhanced states of awareness. This enhanced awareness can lead to changes in preexisting behavioral patterns which could be beneficial in the treatment of substance use disorders (SUDs). Preclinical and clinical studies suggest that ketamine and psychedelics may alter markers associated with synaptic density, and that these changes may underlie effects such as sensitization, conditioned place preference, drug self-administration, and verbal memory performance. In this scoping review, we examined studies that measured synaptic markers in animals and humans after exposure to ketamine and/or psychedelics.

Methods

A systematic search was conducted following PRISMA guidelines, through PubMed, EBSCO, Scopus, and Web of Science, based on a published protocol (Open Science Framework, DOI: 10.17605/OSF.IO/43FQ9). Both in vivo and in vitro studies were included. Studies on the following synaptic markers were included: dendritic structural changes, PSD-95, synapsin-1, synaptophysin-1, synaptotagmin-1, and SV2A.

Results

Eighty-four studies were included in the final analyses. Seventy-one studies examined synaptic markers following ketamine treatment, nine examined psychedelics, and four examined both. Psychedelics included psilocybin/psilocin, lysergic acid diethylamide, N,N-dimethyltryptamine, 2,5-dimethoxy-4-iodoamphetamine, and ibogaine/noribogaine. Mixed findings regarding synaptic changes in the hippocampus and prefrontal cortex (PFC) have been reported when ketamine was administered in a single dose under basal conditions. Similar mixed findings were seen under basal conditions in studies that used repeated administration of ketamine. However, studies that examined animals during stressful conditions found that a single dose of ketamine counteracted stress-related reductions in synaptic markers in the hippocampus and PFC. Repeated administration of ketamine also counteracted stress effects in the hippocampus. Psychedelics generally increased synaptic markers, but results were more consistently positive for certain agents.

Conclusion

Ketamine and psychedelics can increase synaptic markers under certain conditions. Heterogeneous findings may relate to methodological differences, agents administered (or different formulations of the same agent), sex, and type of markers. Future studies could address seemingly mixed results by using meta-analytical approaches or study designs that more fully consider individual differences.

Effect of early embryonic exposure to morphine on defects in the GABAergic system of day-old chicks

Embryonic morphine exposure (EME) leads to abnormal brain development and behavior in the offspring, and the functional alteration of γ-aminobutyric acid (GABA) system is considered to be one of the important mechanisms. To mimic the problem of susceptibility of human gestational drug abuse on addictive drugs in offspring, we administered morphine exposure on days 5-8 and 13-16 of chicken embryo development and examined the functions of GABA neurons and their receptors in postnatal chicks by neuroelectrophysiology, immunohistochemistry and behavioral methods. We found that morphine exposure during embryonic stages 5-8 (MorphineE5-8) significantly reduced the incidence of spontaneous inhibitory postsynaptic potentiation (IPSP) and the induction of evoked IPSP and the mean amplitude of GABA_A agonist muscimol-induced response in the intermediate medial interstitial (IMM) region, compared to naïve controls or saline-exposed chicks. The results of immunocytochemistry further suggest that MorphineE5-8 decreased the synaptic density of GAD-expressing sites in the IMM, while increased the expression of the GABA_A receptor subtype γ2 isoform. Behavioral results found that Morphine5-8 treatment de-inhibited morphine-induced psychomotor responses in postnatal chicks. Morphine exposure at embryonic stages 13-16 (MorphineE13-16) showed no significant changes in the above indicators compared to the saline group. Evidence suggests that early embryonic morphine exposure leads to defects in GABAergic function in the IMM, which in turn alters the responsiveness of postnatal chicks to addictive drugs. These results will help to understand the GABA mechanisms by which embryonic addictive drug exposure contributes to offspring susceptibility to addiction.

Quantity and duration of exposure to general anesthesia for pediatric patients with retinoblastoma

PURPOSE

To quantify the duration of anesthesia required for optimal management of retinoblastoma (Rb), stratified by clinical factors.

METHODS

The medical records of Rb patients treated at Phoenix Children's Hospital between January 2011 and January 2022 were reviewed retrospectively. Demographic, tumor, and treatment data were collected. Anesthesia time was recorded for procedures requiring general anesthesia, including intra-arterial chemotherapy (IAC), enucleation, brainstem auditory evoked response testing (BAER), port placement, magnetic resonance imaging (MRI), and examination under anesthesia (EUA). Descriptive statistics were used to summarize patient and clinical characteristics.

RESULTS

Total anesthesia time was 48,991 minutes for 610 procedures in 43 patients. The median follow-up time was 36 months (range, 12-114 months). Average anesthetic durations per exposure were 274, 152, 81.8, 62.5, 60.7, and 45 minutes for IAC, enucleation, BAER, port placement, MRI, and EUA, respectively. Patients with bilateral Rb underwent a median of 1,659 minutes of total anesthesia, compared with 397 minutes for those with unilateral disease. In patients with unilateral Rb, median total anesthesia time was 2,651, 1681, 312, 397 minutes for International Classification of Retinoblastoma grades B, C, D, and E tumors, respectively. Patients who received IAC as their primary treatment had the highest median anesthesia duration (2,100 minutes), followed by systemic chemo (654 minutes) and enucleation (289 minutes).

CONCLUSIONS

Treatment of Rb requires prolonged and repeated exposure to general anesthesia. Future studies are required to determine the potential effects of these childhood anesthetic exposures.

The impact of early exposure to general anesthesia on visual and neurocognitive development

Every year millions of children are exposed to general anesthesia while undergoing surgical and diagnostic procedures. In the field of ophthalmology, 44,000 children are exposed to general anesthesia annually for strabismus surgery alone. While it is clear that general anesthesia is necessary for sedation and pain minimization during surgical procedures, the possibility of neurotoxic impairments from its exposure is of concern. In animals there is strong evidence linking early anesthesia exposure to abnormal neural development. but in humans the effects of anesthesia are debated. In humans many aspects of vision develop within the first year of life, making the visual system vulnerable to early adverse experiences and potentially vulnerable to early exposure to general anesthesia. We attempt to address whether the visual system is affected by early postnatal exposure to general anesthesia. We first summarize key mechanisms that could account for the neurotoxic effects of general anesthesia on the developing brain and review existing literature on the effects of early anesthesia exposure on the visual system in both animals and humans and on neurocognitive development in humans. Finally, we conclude by proposing future directions for research that could address unanswered questions regarding the impact of general anesthesia on visual development.

Safety of general anaesthetics on the developing brain: are we there yet?

Thirty years ago, neurotoxicity induced by general anaesthetics in the developing brain of rodents was observed. In both laboratory-based and clinical studies, many conflicting results have been published over the years, with initial data confirming both histopathological and neurodevelopmental deleterious effects after exposure to general anaesthetics. In more recent years, animal studies using non-human primates and new human cohorts have identified some specific deleterious effects on neurocognition. A clearer pattern of neurotoxicity seems connected to exposure to repeated general anaesthesia. The biochemistry involved in this neurotoxicity has been explored, showing differential effects of anaesthetic drugs between the developing and developed brains. In this narrative review, we start with a comprehensive description of the initial concerning results that led to recommend that any non-essential surgery should be postponed after the age of 3 yr and that research into this subject should be stepped up. We then focus on the neurophysiology of the developing brain under general anaesthesia, explore the biochemistry of the observed neurotoxicity, before summarising the main scientific and clinical reports investigating this issue. We finally discuss the GAS trial, the importance of its results, and some potential limitations that should not undermine their clinical relevance. We finally suggest some key points that could be shared with parents, and a potential research path to investigate the biochemical effects of general anaesthesia, opening up perspectives to understand the neurocognitive effects of repetitive exposures, especially in at-risk children.

Early Developmental PMCA2b Expression Protects From Ketamine-Induced Apoptosis and GABA Impairments in Differentiating Hippocampal Progenitor Cells

PMCA2 is not expressed until the late embryonic state when the control of subtle Ca²⁺ fluxes becomes important for neuronal specialization. During this period, immature neurons are especially vulnerable to degenerative insults induced by the N-methyl-D-aspartate (NMDA) receptor blocker, ketamine. As H19-7 hippocampal progenitor cells isolated from E17 do not express the PMCA2 isoform, they constitute a valuable model for studying its role in neuronal development. In this study, we demonstrated that heterologous expression of PMCA2b enhanced the differentiation of H19-7 cells and protected from ketamine-induced death. PMCA2b did not affect resting [Ca²⁺]_c in the presence or absence of ketamine and had no effect on the rate of Ca²⁺ clearance following membrane depolarization in the presence of the drug. The upregulation of endogenous PMCA1 demonstrated in response to PMCA2b expression as well as ketamine-induced PMCA4 depletion were indifferent to the rate of Ca²⁺ clearance in the presence of ketamine. Yet, co-expression of PMCA4b and PMCA2b was able to partially restore Ca²⁺ extrusion diminished by ketamine. The profiling of NMDA receptor expression showed upregulation of the NMDAR1 subunit in PMCA2b-expressing cells and increased co-immunoprecipitation of both proteins following ketamine treatment. Further microarray screening demonstrated a significant influence of PMCA2b on GABA signaling in differentiating progenitor cells, manifested by the unique regulation of several genes key to the GABAergic transmission. The overall activity of glutamate decarboxylase remained unchanged, but Ca²⁺-induced GABA release was inhibited in the presence of ketamine. Interestingly, PMCA2b expression was able to reverse this effect. The mechanism of GABA secretion normalization in the presence of ketamine may involve PMCA2b-mediated inhibition of GABA transaminase, thus shifting GABA utilization from energetic purposes to neurosecretion. In this study, we show for the first time that developmentally controlled PMCA expression may dictate the pattern of differentiation of hippocampal progenitor cells. Moreover, the appearance of PMCA2 early in development has long-standing consequences for GABA metabolism with yet an unpredictable influence on GABAergic neurotransmission during later stages of brain maturation. In contrast, the presence of PMCA2b seems to be protective for differentiating progenitor cells from ketamine-induced apoptotic death.

HC. Relevance of Cortical and Hippocampal Interneuron Functional Diversity to General Anesthetic Mechanisms: A Narrative Review

General anesthetics disrupt brain processes involved in consciousness by altering synaptic patterns of excitation and inhibition. In the cerebral cortex and hippocampus, GABAergic inhibition is largely mediated by inhibitory interneurons, a heterogeneous group of specialized neuronal subtypes that form characteristic microcircuits with excitatory neurons. Distinct interneuron subtypes regulate specific excitatory neuron networks during normal behavior, but how these interneuron subtypes are affected by general anesthetics is unclear. This narrative review summarizes current principles of the synaptic architecture of cortical and interneuron subtypes, their contributions to different forms of inhibition, and their roles in distinct neuronal microcircuits. The molecular and cellular targets in these circuits that are sensitive to anesthetics are reviewed in the context of how anesthetics impact interneuron function in a subtype-specific manner. The implications of this functional interneuron diversity for mechanisms of anesthesia are discussed, as are their implications for anesthetic-induced changes in neural plasticity and overall brain function.

HDAC6 is critical for ketamine-induced impairment of dendritic and spine growth in GABAergic projection neurons

Ketamine is widely used in infants and children for anesthesia; both anesthetic and sub-anesthetic doses of ketamine have been reported to preferentially inhibit the GABAergic neurons. Medium spiny neurons (MSNs), the GABAergic projection neurons in the striatum, are vulnerable to anesthetic exposure in the newborn brain. Growth of dendrites requires a deacetylase to remove acetyl from tubulin in the growth cone to destabilize the tubulin. Histone deacetylase 6 (HDAC6) affects microtubule dynamics, which are involved in neurite elongation. In this study we used a human induced pluripotent stem cells (iPSCs)-derived striatal GABA neuron system to investigate the effects of ketamine on HDAC6 and the morphological development of MSNs. We showed that exposure to ketamine (1-500 μM) decreased dendritic growth, dendrite branches, and dendritic spine density in MSNs in a time- and concentration-dependent manner. We revealed that ketamine treatment concentration-dependently inhibited the expression of HDAC6 or aberrantly translocated HDAC6 into the nucleus. Ketamine inhibition on HDAC6 resulted in α-tubulin hyperacetylation, consequently increasing the stability of microtubules and delaying the dendritic growth of MSNs. Finally, we showed that the effects of a single-dose exposure on MSNs were reversible and lasted for at least 10 days. This study reveals a novel role of HDAC6 as a regulator for ketamine-induced deficits in the morphological development of MSNs and provides an innovative method for prevention and treatment with respect to ketamine clinical applications.

Behavioural impairments after exposure of neonatal mice to propofol are accompanied by reductions in neuronal activity in cortical circuitry

BACKGROUND

Both animal and retrospective human studies have linked extended and repeated general anaesthesia during early development with cognitive and behavioural deficits later in life. However, the neuronal circuit mechanisms underlying this anaesthesia-induced behavioural impairment are poorly understood.

METHODS

Neonatal mice were administered one or three doses of propofol, a commonly used i.v. general anaesthetic, over Postnatal days 7-11. Control mice received Intralipid® vehicle injections. At 4 months of age, the mice were subjected to a series of behavioural tests, including motor learning. During the process of motor learning, calcium activity of pyramidal neurones and three classes of inhibitory interneurones in the primary motor cortex were examined in vivo using two-photon microscopy.

RESULTS

Repeated, but not a single, exposure of neonatal mice to propofol i.p. caused motor learning impairment in adulthood, which was accompanied by a reduction of pyramidal neurone number and activity in the motor cortex. The activity of local inhibitory interneurone networks was also altered: somatostatin-expressing and parvalbumin-expressing interneurones were hypoactive, whereas vasoactive intestinal peptide-expressing interneurones were hyperactive when the mice were performing a motor learning task. Administration of low-dose pentylenetetrazol to attenuate γ-aminobutyric acid A receptor-mediated inhibition or CX546 to potentiate α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-subtype glutamate receptor function during emergence from anaesthesia ameliorated neuronal dysfunction in the cortex and prevented long-term behavioural deficits.

CONCLUSIONS

Repeated exposure of neonatal mice to propofol anaesthesia during early development causes cortical circuit dysfunction and behavioural impairments in later life. Potentiation of neuronal activity during recovery from anaesthesia reduces these adverse effects of early-life anaesthesia.

Fundamentals and innovations in regional anaesthesia for infants and children

Regional anaesthesia in children has evolved rapidly in the last decade. Although it previously consisted of primarily neuraxial techniques, the practice now incorporates advanced peripheral nerve blocks, which were only recently described in adults. These novel blocks provide new avenues for providing opioid-sparing analgesia while minimising invasiveness, and perhaps risk, associated with older techniques. At the same time, established methods, such as infant spinal anaesthesia, under-utilised in the last 20 years, are experiencing a revival. The impetus has been the concern regarding the potential long-term neurocognitive effects of general anaesthesia in the young child. These techniques have expanded from single shot spinal anaesthesia to combined spinal/epidural techniques, which can now effectively provide surgical anaesthesia for procedures below the umbilicus for a prolonged period of time, thereby avoiding the need for general anaesthesia. Continuous 2-chloroprocaine infusions, previously only described for intra-operative regional anaesthesia, have gained popularity as a means of providing prolonged postoperative analgesia in epidural and continuous nerve block techniques. The rapid, liver-independent metabolism of 2-chloroprocaine makes it ideal for prolonged local anaesthetic infusions in neonates and small infants, obviating the increased risk of local anaesthetic systemic toxicity that occurs with amide local anaesthetics. Debate continues over certain practices in paediatric regional anaesthesia. While the rarity of complications makes comparative analyses difficult, data from large prospective registries indicate that providing regional anaesthesia to children while under general anaesthesia appears to be at least as safe as in the sedated or awake patient. In addition, the estimated frequency of serious adverse events demonstrates that regional blocks in children under general anaesthesia are no less safe than in awake adults. In infants, the techniques of direct thoracic epidural placement or caudal placement with cephalad threading each have distinct advantages and disadvantages. As the data cannot support the safety of one technique over the other, the site of epidural insertion remains largely a matter of anaesthetist discretion.

Reversal of Age-Related Neuronal Atrophy by α5-GABAA Receptor Positive Allosteric Modulation

Aging is associated with reduced brain volume, altered neural activity, and neuronal atrophy in cortical-like structures, comprising the frontal cortex and hippocampus, together contributing to cognitive impairments. Therapeutic efforts aimed at reversing these deficits have focused on excitatory or neurotrophic mechanisms, although recent findings show that reduced dendritic inhibition mediated by α5-subunit containing GABA-A receptors (α5-GABAA-Rs) occurs during aging and contributes to cognitive impairment. Here, we aimed to confirm the beneficial effect on working memory of augmenting α5-GABAA-R activity in old mice and tested its potential at reversing age-related neuronal atrophy. We show that GL-II-73, a novel ligand with positive allosteric modulatory activity at α5-GABAA-R (α5-PAM), increases dendritic branching complexity and spine numbers of cortical neurons in vitro. Using old mice, we confirm that α5-PAM reverses age-related working memory deficits and show that chronic treatment (3 months) significantly reverses age-related dendritic shrinkage and spine loss in frontal cortex and hippocampus. A subsequent 1-week treatment cessation (separate cohort) resulted in loss of efficacy on working memory but maintained morphological neurotrophic effects. Together, the results demonstrate the beneficial effect on working memory and neurotrophic efficacy of augmenting α5-GABAA-R function in old mice, suggesting symptomatic and disease-modifying potential in age-related brain disorders.

Maternal surgery during pregnancy has a transient adverse effect on the developing fetal rabbit brain

BACKGROUND

Recently, the US Food and Drug Administration called for cautious use of anesthetic drugs during pregnancy. In 0.2-2% of pregnancies, nonobstetric surgery is being performed. The consequences of anesthesia during pregnancy on fetal development remain unclear, and preclinical studies in relevant animal models may help to elucidate them.

OBJECTIVE

To assess the effect of maternal anesthesia and surgery during pregnancy on the developing fetal brain, using a rabbit model.

MATERIALS AND METHODS

This is a randomized, sham-controlled study in time-mated pregnant does at 28 days of gestation (term = 31 days), which corresponds to the end of the second trimester in humans. Anesthesia was induced in 14 does (155 pups) with propofol and maintained with 4 vol% (equivalent to 1 minimum alveolar concentration) sevoflurane for 2 hours, and a laparotomy with minimal organ manipulation was performed (surgery group). Maternal vital signs (blood pressure, heart rate, peripheral and cerebral oxygen saturation, temperature, end-tidal CO₂, pH, lactate) were continuously monitored. Sham controls consisted of 7 does (74 pups) undergoing invasive hemodynamic monitoring for 2 hours without sedation. At term, does underwent cesarean delivery under ketamine-medetomidine sedation and local anesthesia. Pups either underwent motor and sensory neurologic testing followed by euthanasia at day 1 or daily neurodevelopment testing for 2 weeks and extensive neurologic assessment at 5 and 7 weeks (open field and object recognition test, T-maze, and radial-arm maze). Brains were harvested for histologic assessment of neuron density and synaptophysin expression.

RESULTS

Blood gases and vital parameters were stable in both groups. On postnatal day 1, surgery pups had significant lower motor (25 ± 1 vs 23 ± 3; P = .004) and sensory (16 ± 2 vs 15 ± 2; P = .005) neurobehavioral scores and lower brain-to-body weight ratios (3.7% ± 0.6% vs 3.4% ± 0.6%; P = .001). This was accompanied by lower neuron density in multiple brain regions (eg, hippocampus 2617 ± 410 vs 2053 ± 492 neurons/mm²; P = .004) with lower proliferation rates and less synaptophysin expression. Furthermore, surgery pups had delayed motor development during the first week of life, for example with hopping appearing later (6 ± 5 vs 12 ± 3 days; P = .011). Yet, by 7 weeks of age, neurobehavioral impairment was limited to a reduced digging behavior, and no differences in neuron density or synaptophysin expression were seen.

CONCLUSION

In rabbits, 2 hours of maternal general anesthesia and laparotomy, with minimal organ and no fetal manipulation, had a measurable impact on neonatal neurologic function and brain morphology. Pups had a slower motoric neurodevelopment, but by 7 weeks the effect became almost undetectable.

Anesthesia for pediatric ophthalmologic surgery

This review presents updated recommendations, based on existing clinical research, for anesthetic management of strabismus surgery in children. In children, unlike adults, eye surgery nearly always requires general anesthesia, even for brief procedures. Recommendations for preoperative anxiolysis, fasting guidelines, and management of upper respiratory infections are discussed. Airway considerations and the oculocardiac reflex are highlighted. The prevention of postoperative complications, including those related to opioid prescription therapy, is also addressed. Finally, given the 2016 warning from the Food and Drug Administration about anesthesia neurotoxicity in children, we discuss recent studies on anesthetic neurotoxicity in children undergoing general anesthesia.

Effects of Perinatal Exposure to Ketamine on the Developing Brain

Initially used as an analgesic and anesthetic, ketamine has unfortunately been abused as a popular recreational party drug due to its psychotropic effects. Over the last decade, ketamine has also emerged as an effective rapid-onset anti-depressant. The increasingly widespread use and misuse of the drug in infants and pregnant women has posed a concern about the neurotoxicity of ketamine to the immature brains of developing fetuses and children. In this review, we summarize recent research findings on major possible mechanisms of perinatal ketamine-induced neurotoxicity. We also briefly summarize the neuroprotective effects of ketamine in the presence of noxious stimuli. Future actions include implementation of more drug abuse education and prevention campaigns to raise the public’s awareness of the harmful effects of ketamine abuse; further investigations to justify the clinical use of ketamine as analgesic, anesthetic and anti-depressant; and further studies to develop alternatives to ketamine or treatments that can alleviate the detrimental effects of ketamine use, especially in infants and pregnant women.

Nonanesthetic Effects of Ketamine: A Review Article

Ketamine is considered a dissociative anesthetic medication, and it is commonly administered by a parenteral route. It works mainly by blocking the N-methyl-D-aspartate receptor. It inhibits the voltage-gated Na and K channels and serotonin and dopamine reuptake; also, it affects specific receptors, such as α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid, kainate, and aminobutyric acid A receptors. Ketamine appears to have particular mechanisms that are potentially involved during analgesic induction, including enhancing of descending inhibition and antiinflammatory effects. More recently, it has been shown that ketamine has potential in clinical practice for the management of chronic pain, cognitive function, depression, acute brain injury, and disorders of the immune system.

General Anesthesia and Young Brain: What is New?

Considering that growing population of very young children is exposed to general anesthesia every year, it is of utmost importance to understand how and whether such practice may affect the development and growth of their very immature and vulnerable brains. Compelling evidence from animal studies suggests that an early exposure to general anesthesia is detrimental to normal brain development leading to structural and functional impairments of neurons and glia, and long-lasting impairments in normal emotional and cognitive development. Although the evidence from animal studies is overwhelming and confirmed across species examined from rodents to non-human primates, the evidence from human studies is inconsistent and not conclusive at present. In this review we focus on new developments in animal studies of anesthesia-induced developmental neurotoxicity and summarize recent clinical studies while focusing on outcome measures and exposure variables in terms of their utility for assessing cognitive and behavioral development in children.

Biomarkers, Genetics, and Epigenetic Studies to Explore the Neurocognitive Effects of Anesthesia in Children

Exposure to commonly used anesthetic agents causes widespread neuronal degeneration in the developing mammalian brain and has been shown to impair neurodevelopment in a variety of newborn vertebrate animal species. Although retrospective studies have suggested an association between anesthesia exposure in childhood and subsequent neurodevelopmental abnormalities, a causal relationship in humans has yet to be demonstrated. Unfortunately, translation of findings from bench to bedside is limited by several factors and histologic assessment in healthy children following exposure to anesthesia is not possible. Therefore, to prove that anesthesia-induced neurotoxicity occurs in humans, alternative approaches are necessary. Here we present the summary of a focus group discussion regarding the utility of biomarkers in translational studies of anesthetic neurotoxicity as part of The 2016 Pediatric Anesthesia NeuroDevelopmental Assessment (PANDA) Symposium at Columbia University Medical Center. The experts agreed that defining intermediate phenotypes using advanced neuroimaging as a biomarker is a highly feasible and reasonable modality to provide new insights into the deleterious effects of anesthetic exposure in the developing human brain and could illuminate a viable investigative path forward. Ultimately, well-defined intermediate phenotypes may allow us to fully understand the neurodevelopmental impact of anesthesia-induced neurotoxicity and permit us to develop the safest and most effective anesthetic strategies for the infants and children we care for.

A systematic review of methodology applied during preclinical anesthetic neurotoxicity studies: important issues and lessons relevant to the design of future clinical research

Preclinical evidence suggests that anesthetic agents harm the developing brain thereby causing long-term neurocognitive impairments. It is not clear if these findings apply to humans, and retrospective epidemiological studies thus far have failed to show definitive evidence that anesthetic agents are harmful to the developing human brain.

AIM

The aim of this systematic review was to summarize the preclinical studies published over the past decade, with a focus on methodological issues, to facilitate the comparison between different preclinical studies and inform better design of future trials.

METHOD

The literature search identified 941 articles related to the topic of neurotoxicity. As the primary aim of this systematic review was to compare methodologies applied in animal studies to inform future trials, we excluded a priori all articles focused on putative mechanism of neurotoxicity and the neuroprotective agents. Forty-seven preclinical studies were finally included in this review.

RESULTS

Methods used in these studies were highly heterogeneous-animals were exposed to anesthetic agents at different developmental stages, in various doses and in various combinations with other drugs, and overall showed diverse toxicity profiles. Physiological monitoring and maintenance of physiological homeostasis was variable and the use of cognitive tests was generally limited to assessment of specific brain areas, with restricted translational relevance to humans.

CONCLUSION

Comparison between studies is thus complicated by this heterogeneous methodology and the relevance of the combined body of literature to humans remains uncertain. Future preclinical studies should use better standardized methodologies to facilitate transferability of findings from preclinical into clinical science.

Beyond anesthetic properties: the effects of isoflurane on brain cell death, neurogenesis, and long-term neurocognitive function

Anesthetic drugs cause brain cell death and long-term neurocognitive dysfunction in neonatal rats. Recently, human data also suggest that anesthesia early in life may cause cognitive impairment. The connection between cell death and neurocognitive decline is uncertain. It is conceivable that mechanisms other than brain cell death contribute to neurocognitive outcome of neonatal anesthesia. In a series of experiments, we demonstrate that isoflurane exposure causes significant hypercarbia in postnatal day 7 rats and that exposure to isoflurane or carbon dioxide for 4 h provoked brain cell death. However, 1 h of isoflurane exposure was not sufficient to cause brain cell death. Moreover, only 4 h of isoflurane exposure, but not 1 or 2 h of exposure or 4 h of carbon dioxide, led to impaired hippocampal function,questioning the association between anesthesia-induced brain cell death and neurocognitive dysfunction. Neurogenesis both in the developing and adult dentate gyrus is important for hippocampal function, specifically learning and memory. γ-Amino-butyric-acid regulates proliferation and neuronal differentiation both in the developing and the adult brain. Inhaled anesthetics are γ-amino-butyric-acid-ergic and may therefore affect neurogenesis, which could be an alternative mechanism mediating anesthesia-induced neurocognitive decline in immature rats. Understanding the mechanism will help guide clinical trials aiming to define the scope of the problem in humans and may lead to preventive and therapeutic strategies.

Preliminary evaluation of clinical outcome and safety of ketamine as an anesthetic for electroconvulsive therapy in schizophrenia

OBJECTIVES

Electroconvulsive therapy (ECT) is an effective and safe option in the treatment of affective disorders and schizophrenia. One parameter known to influence ECT treatment efficacy is the choice of narcotic, and ketamine has emerged as an interesting alternative to conventional anaesthetics like barbiturates since it does not negatively influence seizure threshold. However, due to the potential to provoke dissociative symptoms, ketamine anaesthesia is rather hesitantly used in schizophrenia patients for fear of causing disease exacerbation.

METHODS

We retrospectively investigated clinical outcome and safety in patients treated with ECT for schizophrenia and receiving ketamine anaesthesia, either exclusively or as switch from another narcotic and compared seizure parameters to a group of ECT-treated schizophrenia patients with thiopental anaesthesia.

RESULTS

In none of the six patients undergoing ECT with ketamine did we observe disease exacerbation, and except for one patient, all patients responded or remitted under ECT. A preliminary analysis of seizure parameters shows an association with longer seizures in patients exclusively receiving ketamine.

CONCLUSIONS

While the small sample size and retrospective character are limitations of our study, our preliminary results nonetheless challenge wide-spread preconceptions about the use of ketamine in schizophrenia patients and encourage further research into the option of using ketamine anaesthesia for ECT.

Neonatal ketamine exposure causes impairment of long-term synaptic plasticity in the anterior cingulate cortex of rats

Ketamine, a dissociative anesthetic most commonly used in many pediatric procedures, has been reported in many animal studies to cause widespread neuroapoptosis in the neonatal brain after exposure in high doses and/or for a prolonged period. This neurodegenerative change occurs most severely in the forebrain including the anterior cingulate cortex (ACC) that is an important brain structure for mediating a variety of cognitive functions. However, it is still unknown whether such apoptotic neurodegeneration early in life would subsequently impair the synaptic plasticity of the ACC later in life. In this study, we performed whole-cell patch-clamp recordings from the ACC brain slices of young adult rats to examine any alterations in long-term synaptic plasticity caused by neonatal ketamine exposure. Ketamine was administered at postnatal day 4-7 (subcutaneous injections, 20mg/kg given six times, once every 2h). At 3-4weeks of age, long-term potentiation (LTP) was induced and recorded by monitoring excitatory postsynaptic currents from ACC slices. We found that the induction of LTP in the ACC was significantly reduced when compared to the control group. The LTP impairment was accompanied by an increase in the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor-mediated excitatory synaptic transmission and a decrease in GABA inhibitory synaptic transmission in neurons of the ACC. Thus, our present findings show that neonatal ketamine exposure causes a significant LTP impairment in the ACC. We suggest that the imbalanced synaptic transmission is likely to contribute to ketamine-induced LTP impairment in the ACC.

Spinal anesthesia in children: A review

Even after a vast safety record, the role of spinal anesthesia (SA) as a primary anesthetic technique in children remains contentious and is mainly limited to specialized pediatric centers. It is usually practiced on moribund former preterm infants (<60 weeks post-conception) to reduce the incidence of post-operative apnea when compared to general anesthesia (GA). However, there is ample literature to suggest its safety and efficacy for suitable procedures in older children as well. SA in children has many advantages as in adults with an added advantage of minimal cardio-respiratory disturbance. Recently, several reports from animal studies have raised serious concerns regarding the harmful effects of GA on young developing brain. This may further increase the utility of SA in children as it provides all components of balanced anesthesia technique. Also, SA can be an economical option for countries with finite resources. Limited duration of surgical anesthesia in children is one of the major deterrents for its widespread use in them. To overcome this, several additives like epinephrine, clonidine, fentanyl, morphine, neostigmine etc. have been used and found to be effective even in neonates. But, the developing spinal cord may also be vulnerable to drug-related toxicity, though this has not been systematically evaluated in children. So, adjuvants and drugs with widest therapeutic index should be preferred in children. Despite its widespread use, incidence of side-effects is low and permanent neurological sequalae have not been reported with SA. Literature yields encouraging results regarding its safety and efficacy. Technical skills and constant vigilance of experienced anesthesia providers is indispensable to achieve good results with this technique.

Ketamine and atropine decrease pain for preterm newborn tracheal intubation in the delivery room: an observational pilot study

AIM

Various analgesic strategies are used before tracheal intubation of preterm newborns in the delivery room, due to the lack of a standard protocol and difficult venous access. This study evaluated the feasibility and efficacy of short venous catheter insertion and immediate ketamine analgesia for tracheal intubation of preterm newborns at birth in the delivery room.

METHODS

Prospective observational pilot study, with ketamine and atropine used at the paediatrician's discretion. Pain score, heart rate, SpO2 nadirs, procedure duration and neonatal intensive care unit morbidity were recorded.

RESULTS

Fifty-seven consecutive preterm newborns were included between January I and June 30, 2012: 15 in the no analgesia group and 39 in the intravenous ketamine group. Short catheter insertion failed in three newborns. The pain score was lower during laryngoscopy in the ketamine group (4 ± 0.7 vs. 2.9 ± 3.2 in the no analgesia group, p < 0.001). The heart rate nadir during tracheal intubation was 150.7 ± 29.6 bpm (vs. 112.6 ± 35.5 bpm in the no analgesia group, p < 0.01). Surfactant therapy was administered to 79.5% of newborns in the ketamine group (vs. 92.3%, p = 0.29) in the first 30 min of life.

CONCLUSION

Short venous catheter insertion with immediate ketamine analgesia plus atropine for tracheal intubation of preterm newborns in the delivery room was effective in decreasing pain and preventing vagal bradycardia.

Regenerative toxicology: the role of stem cells in the development of chronic toxicities

INTRODUCTION

Human stem cell lines and their derivatives, as alternatives to the use of animal cells or cancer cell lines, have been widely discussed as cellular models in predictive toxicology. However, the role of stem cells in the development of long-term toxicities and carcinogenesis has not received great attention so far, despite growing evidence indicating the relationship of stem cell damage to adverse effects later in life. However, testing this in vitro is a scientific/technical challenge in particular due to the complex interplay of factors existing under physiological conditions. Current major research programs in stem cell toxicity are not aiming to demonstrate that stem cells can be targeted by toxicants. Therefore, this knowledge gap needs to be addressed in additional research activities developing technical solutions and defining appropriate experimental designs.

AREAS COVERED

The current review describes selected examples of the role of stem cells in the development of long-term toxicities in the brain, heart or liver and in the development of cancer.

EXPERT OPINION

The presented examples illustrate the need to analyze the contribution of stem cells to chronic toxicity in order to make a final conclusion whether stem cell toxicities are an underestimated risk in mechanism-based safety assessments. This requires the development of predictive in vitro models allowing the assessment of adverse effects to stem cells on chronic toxicity and carcinogenicity.

High-dose glucocorticoid aggravates TBI-associated corticosteroid insufficiency by inducing hypothalamic neuronal apoptosis

Emerging experimental and clinical data suggest that severe illness, such as traumatic brain injury (TBI), can induce critical illness-related corticosteroid insufficiency (CIRCI). However, underlying mechanisms of this TBI-associated CIRCI remain poorly understood. We hypothesized that dexamethasone (DXM), a synthetic glucocorticoid, which was widely used to treat TBI, induces hypothalamic neuronal apoptosis to aggravate CIRCI. To test this hypothesis, we have evaluated the dose effect of DXM (1 or 10mg/kg) on the development of acute CIRCI in rats with fluid percussion injury-induced TBI and on cultured rat hypothalamic neurons in vitro (DXM, 10(-5)-10(-8)mol/L). Corticosterone Increase Index was recorded as the marker for CIRCI. In addition, MTT and TUNEL assays were used to measure the viability and apoptosis of hypothalamic neurons in primary culture. Moreover, high-resolution hopping probe ion conductance microscopy (HPICM) was used to monitor the DXM-induced morphological changes in neurons. The incidence of acute CIRCI was significantly higher in the high-dose DXM group on post-injury day 7. Cellular viability was significantly decreased from 12h to 24h after the treatment with a high-dose of DXM. A significantly increase in TUNEL positive cells were detected in cultured cells treated with a high-dose of DXM after 18h. Neurites of hypothalamic neuron were dramatically thinner and the numbers of dendritic beadings increased in neurons treated with the high dose of DXM for 12h. In conclusion, high-dose DXM induced hypothalamic neurons to undergo apoptosis in vivo and in vitro, which may aggravate TBI-associated CIRCI.

Neurodevelopmental implications of the use of sedation and analgesia in neonates

Laboratory studies have shown that general anesthetics may cause accelerated apoptosis and other adverse morphologic changes in neurons of the developing brain. The mechanism may be related to the neuronal quiescence or inactivity associated with anesthetic exposure. Few data exist on how brief anesthetic exposure may affect neurodevelopment in the newborn. Good evidence however shows that untreated pain and stress have an adverse effect on neurodevelopment, and therefore, at this stage, providing effective analgesia, sedation, and anesthesia would seem to be more important than concern over neurotoxicity.

Modeling anesthetic developmental neurotoxicity using human stem cells

Mounting preclinical evidence in rodents and nonhuman primates has demonstrated that prolonged exposure of developing animals to general anesthetics can induce widespread neuronal cell death followed by long-term memory and learning disabilities. In vitro experimental evidence from cultured neonatal animal neurons confirmed the in vivo findings. However, there is no direct clinical evidence of the detrimental effects of anesthetics in human fetuses, infants, or children. Development of an in vitro neurogenesis system using human stem cells has opened up avenues of research for advancing our understanding of human brain development and the issues relevant to anesthetic-induced developmental toxicity in human neuronal lineages. Recent studies from our group, as well as other groups, showed that isoflurane influences human neural stem cell proliferation and neurogenesis, whereas ketamine induces neuroapoptosis. Application of this high throughput in vitro stem cell neurogenesis approach is a major stride toward ensuring the safety of anesthetic agents in young children. This in vitro human model allows us to (1) screen the toxic effects of various anesthetics under controlled conditions during intense neuronal growth, (2) find the trigger for the anesthetic-induced catastrophic chain of toxic events, and (3) develop prevention strategies to avoid this toxic effect. In this article, we reviewed the current findings in anesthetic-induced neurotoxicity studies, specifically focusing on the in vitro human stem cell model.

Developmental neurotoxicity of ketamine in pediatric clinical use

Ketamine is widely used as an anesthetic, analgesic, and sedative in pediatric clinical practice and it is also listed as an illicit drug by most countries. Recent in vivo and in vitro animal studies have confirmed that ketamine can induce neuronal cell death in the immature brain, resulting from widespread neuronal apoptosis. These effects can disturb normal development further altering the structure and functions of the brain. Our recent studies further indicate that ketamine can alter neurogenesis from neural stem progenitor cells in the developing brain. Taken together, these findings identify a novel complication associated with ketamine use in premature infants, term newborns, and pregnant women. Recent data on the developmental neurotoxicity of ketamine are reviewed with proposed future directions for evaluating the safety of ketamine in these patient populations.

Ketamine enhances human neural stem cell proliferation and induces neuronal apoptosis via reactive oxygen species-mediated mitochondrial pathway

BACKGROUND

Growing evidence indicates that ketamine causes neurotoxicity in a variety of developing animal models, leading to a serious concern regarding the safety of pediatric anesthesia. However, if and how ketamine induces human neural cell toxicity is unknown. Recapitulation of neurogenesis from human embryonic stem cells (hESCs) in vitro allows investigation of the toxic effects of ketamine on neural stem cells (NSCs) and developing neurons, which is impossible to perform in humans. In the present study, we assessed the influence of ketamine on the hESC-derived NSCs and neurons.

METHODS

hESCs were directly differentiated into neurons via NSCs. NSCs and 2-week-old neurons were treated with varying doses of ketamine for different durations. NSC proliferation capacity was analyzed by Ki67 immunofluorescence staining and bromodeoxyuridine assay. Neuroapoptosis was analyzed by TUNEL staining and caspase 3 activity measurement. The mitochondria-related neuronal apoptosis pathway including mitochondrial membrane potential, cytochrome c distribution within cells, mitochondrial fission, and reactive oxygen species (ROS) production were also investigated.

RESULTS

Ketamine (100 µM) increased NSC proliferation after 6-hour exposure. However, significant neuronal apoptosis was only observed after 24 hours of ketamine treatment. In addition, ketamine decreased mitochondrial membrane potential and increased cytochrome c release from mitochondria into cytosol. Ketamine also enhanced mitochondrial fission as well as ROS production compared with no-treatment control. Importantly, Trolox, a ROS scavenger, significantly attenuated the increase of ketamine-induced ROS production and neuronal apoptosis.

CONCLUSIONS

These data for the first time demonstrate that (1) ketamine increases NSC proliferation and causes neuronal apoptosis; (2) mitochondria are involved in ketamine-induced neuronal toxicity, which can be prevented by Trolox; and (3) the stem cell-associated neurogenesis system may provide a simple and promising in vitro model for rapidly screening anesthetic neurotoxicity and studying the underlying mechanisms as well as prevention strategies to avoid this toxic effect.

Feasibility and pilot study of the Pediatric Anesthesia NeuroDevelopment Assessment (PANDA) project

BACKGROUND

Animal studies have documented that exposure of the developing brain to commonly used anesthetic agents induces neurotoxicity and late abnormal neurobehavioral functions as adults. Results from clinical studies have all been analyzed using existing data sets, and these studies produced inconsistent results. To provide more definitive evidence to address the clinical relevance of anesthetic neurotoxicity in children, an interdisciplinary team of investigators designed and developed the Pediatric Anesthesia NeuroDevelopment Assessment (PANDA) project. We present pilot study results in 28 sibling pairs recruited and tested at the Columbia University Medical Center (CUMC) and Children's Hospital of Boston (CHB) for the PANDA project.

METHODS

The PANDA project uses an ambidirectional cohort design. We performed prospective neuropsychological assessment in 28 exposed-unexposed sibling pairs from 6 to 11 years of age. The exposed siblings were ASA 1 or 2 and had received a single episode of anesthesia for inguinal hernia repair before the age of 36 months and the unexposed siblings had no anesthesia before the age of 36 months. All the sibling pairs were English speaking and were 36 weeks of gestational age or older. Each sibling pair underwent a direct testing using the Wechsler Abbreviated Scale of Intelligence (WASI) and the NEuroPSYchological Assessment, second edition (NEPSY II), and the parents completed questionnaires related to behavior using CBCL and Conners rating. Data are presented as means±SD. We conducted descriptive analyses of the demographic data. We compared both the exposed and the unexposed sibling groups on WASI and NEPSY II, and total and T scores from CBCL and Conners rating were analyzed as continuous data using the paired t test between the two groups. A P<0.05 was considered significant.

RESULTS

After the Institutional Review Board approval for the study at both CUMC and CHB, the full PANDA study protocol was implemented to perform a pilot feasibility study. Our success rate was 96.7% in obtaining detailed medical and anesthesia records in our historical cohort. The scores for verbal IQ (exposed=106.1±16.3, unexposed=109.2±17.9), performance IQ (exposed=109.1±16.0, unexposed=113.9±15.9), and full IQ (exposed=108.2±14.0, unexposed=112.8±16.8) were comparable between the siblings. There were no differences between the two groups in T scores for any of the NEPSY II subdomains, CBCL, or Conners rating. An abstraction protocol with web-based electronic data capture forms also was developed in conjunction with the International Center for Health Outcomes and Innovation Research (InCHOIR).

CONCLUSIONS

The pilot study provided useful information for feasibility to recruit the sample size and to obtain relevant clinical data. For the final study protocol, both the neuropsychological battery and the age range for testing were revised. Our results confirmed the feasibility of our study approach and yielded pilot data from neuropsychological testing.

Micropatterned surfaces: techniques and applications in cell biology

IMPORTANCE OF THE FIELD

Engineering of cell culture substrates provides a unique opportunity for precise control of the cellular microenvironment with both spatial as well as temporal resolutions. This greatly enhances studies of cell-cell, cell-matrix and cell-factor interaction studies in vitro.

AREAS COVERED IN THIS REVIEW

The technologies used for micropatterning in the biological field over the last decade and new applications in the last few years for dynamic control of surfaces, tissue engineering, drug discovery, cell-cell interactions and stem cell studies are presented.

WHAT THE READER WILL GAIN

The reader will gain knowledge on the state of the art in micropatterning and its wide ranging applications in cell patterning, with new pathways to control the cell environment.

TAKE HOME MESSAGE

Micropatterning of cells has been studied and developed enough to be widely applied ranging from single cell assays to tissue engineering. Techniques have evolved from many-step processes to direct writing of biologically selective patterns.

Neuraxial analgesia in neonates and infants: a review of clinical and preclinical strategies for the development of safety and efficacy data

Neuraxial drugs provide robust pain control, have the potential to improve outcomes, and are an important component of the perioperative care of children. Opioids or clonidine improves analgesia when added to perioperative epidural infusions; analgesia is significantly prolonged by the addition of clonidine, ketamine, neostigmine, or tramadol to single-shot caudal injections of local anesthetic; and neonatal intrathecal anesthesia/analgesia is increasing in some centers. However, it is difficult to determine the relative risk-benefit of different techniques and drugs without detailed and sensitive data related to analgesia requirements, side effects, and follow-up. Current data related to benefits and complications in neonates and infants are summarized, but variability in current neuraxial drug use reflects the relative lack of high-quality evidence. Recent preclinical reports of adverse effects of general anesthetics on the developing brain have increased awareness of the potential benefit of neuraxial anesthesia/analgesia to avoid or reduce general anesthetic dose requirements. However, the developing spinal cord is also vulnerable to drug-related toxicity, and although there are well-established preclinical models and criteria for assessing spinal cord toxicity in adult animals, until recently there had been no systematic evaluation during early life. Therefore, in the second half of this review, we present preclinical data evaluating age-dependent changes in the pharmacodynamic response to different spinal analgesics, and recent studies evaluating spinal toxicity in specific developmental models. Finally, we advocate use of neuraxial drugs with the widest demonstrable safety margin and suggest minimum standards for preclinical evaluation before adoption of new analgesics or preparations into routine clinical practice.

Developmental neurotoxicity screening using human embryonic stem cells

Research in the area of stem cell biology and regenerative medicine, along with neuroscience, will further our understanding of drug-induced death of neurons during their development. With the development of an in vitro model of stem cell-derived human neural cell lines investigators can, under control conditions and during intense neuronal growth, examine molecular mechanisms of various drugs and conditions on early developmental neuroapoptosis in humans. If the use of this model will lead to fewer risks, or identification of drugs and anesthetics that are less likely to cause the death of neurons, this approach will be a major stride toward assuring the safety of drugs during the brain development. The ultimate goal would be not only to find the trigger for the catastrophic chain of events, but also to prevent neuronal cell death itself.