Commentary: Early-in-life Isoflurane Exposure Alters Resting-state Functional connectivity in Juvenile Non-human Primates

Viola Neudecker1#, Jose F. Perez-Zoghbi1# and Ansgar M. Brambrink1*

Department of Anesthesiology, Columbia University Medical Center, New York, NY 10032, USA.;

The concern about anesthesia-induced developmental neurotoxicity (AIDN) in infants and young children arises from animal studies indicating potential long-term neurobehavioral impairments following early-in-life anesthesia exposure. While initial clinical studies provided ambiguous results, recent prospective assessments in children indicate associations between early-in-life anesthesia exposure and later behavioral alterations. Ethical constraints and confounding factors in clinical studies pose challenges in establishing a direct causal link and in investigating its mechanisms. This commentary on a recent study in non-human primates (NHPs) focuses on exploring the role of neuroinflammation and alterations in brain functional connectivity in the behavioral impairments following early-in-life anesthesia exposure. In juvenile NHPs, chronic astrogliosis in the amygdala correlates with alterations in functional connectivity between this area with other regions of the brain and with the behavioral impairments, suggesting a potential mechanism for AIDN. Despite acknowledging the study's limitations, these findings emphasize the need for further research with larger cohorts to confirm these associations and to establish a causal link between the neuroinflammation and the behavioral alterations associated with early-in-life anesthesia exposure.

Anesthesia-induced developmental neurotoxicity (AIDN)

There is a concern that anesthesia exposure early in life may be neurotoxic to infants and young children and cause long-term impairments in their neurobehavioral development. This concern originated from preclinical studies in rodents, which found that early-in-life exposure to anesthetics commonly used in pediatric anesthesia caused acute increase of neuroapoptosis and long-term alterations in cognition and behaviors1. Most of these findings also have been observed in non-human primates (NHPs)2-8. In contrast, early clinical studies with retrospective assessments provided ambiguous results, with some suggesting that anesthesia exposure affected primarily cognitive abilities,9-13 while others found no associations. However, most recent clinical studies with prospective assessments have provided some valuable outcomes that indicate an association between early-in-life anesthesia exposure and alterations in behavior later in life,14-16 which have been highlighted in a recent meta-analysis17. Ethical limitations and the presence of numerous confounders in clinical studies make it a challenge to establish a direct causal link between anesthesia exposure and neurodevelopmental deficits in children, as well as to investigate potential mechanisms. Therefore, we designed a study in NHPs that were anesthetized during infancy under conditions that resemble those in the pediatric operating room, to investigate alterations in behaviors and accompanying long-term structural and functional changes in the primate brain. Results from these studies have been published in separate papers18-21. In this commentary on our latest report21 we focus on 1) the potential role of neuroinflammation in the behavioral outcomes associated with early-in-life anesthesia exposure and 2) the alterations in brain functional connectivity, assessed with magnetic resonance imaging (MRI), as a mechanistic link between neuroinflammation and those behavioral alterations.    

Role of neuroinflammation in AIDN

The mechanisms underlying AIDN are not fully understood, but among them anesthesia-induced neuroinflammation has been proposed as a potential contributor to AIDN. Neuroinflammation is a common hallmark of many neurodegenerative and -developmental diseases such as Alzheimer’s disease (AD), dementia, and autism spectrum disorders (ASD)22, 23. Here neuroinflammation plays a role in neuronal dysfunctions including cognitive impairments in neurodegenerative diseases and behavioral alterations in ASD. The neuroinflammatory response involves activation of microglia and astrocytes and commonly elevated cytokines in the brain include interleukin-6 (IL-6) and tumor necrosis factor alpha (TNFa), among others. Several reports documented acute or chronic neuroinflammation after early-in-life anesthesia exposure over the last decade, including studies in rodents and piglets showing acute neuroinflammation with increased microglia activation as well as elevated IL-6, TNFa, and IL-1β in brain tissue after single or repeated exposure to volatile anesthetics early in life24-33. Studies have also reported neuroinflammation present at an adult age in rats after early-in-life exposure to sevoflurane34, 35. In addition, maternal exposure during late pregnancy also causes neuroinflammation in the murine fetal brains and impairments in the offspring’s neurodevelopment36, 37. Consequently, studies applying known anti-inflammatory substances such as inhibitors of the NFκB pathway during early-in-life exposure reported reduced acute neuroinflammation and ameliorated long-term neurodevelopmental impairments24-30, 37. Based on the beneficial effects of pharmacologically reducing the acute inflammatory response of the brain, it’s reasonable to conclude that neuroinflammation plays a significant role in mediating the neurodevelopmental impairments of early-in-life anesthesia exposure in rodents. In NHPs, microglial activation has been detected in infants after exposure to isoflurane using positron emission tomography (PET)38. This inflammatory response lasted for up to 7 days, suggesting that neuroinflammation in the primate brain may play a significant role in the neurodevelopmental impairments that develop later in life. We provided first evidence that neuroinflammation is present in brains of juvenile (2-year-old) NHPs that were exposed to isoflurane early in life (on post-natal day 6). This was revealed as increased GFAP staining of specific brain areas, indicating increased astrocyte activation at this age20. This long-term astrogliosis was found in brain areas known to play an important role for the behavioral alterations the animals displayed at this juvenile age19, suggesting a role for chronic neuroinflammation in mediating the behavioral impairments in NHPs. However, the mechanisms linking neuroinflammation with neurodevelopmental impairments after early-in-life anesthesia exposure were not investigated either in NHPs or in other animals. 

Brain functional connectivity: a link between neuroinflammation and AIDN

Neuronal dysfunction can be reflected as alterations in brain functional connectivity that can be measured by resting-state functional connectivity magnetic resonance imaging (rs-fcMRI). In clinical studies with ASD, AD, and dementia patients, abnormal functional connectivity has been found to be associated with worse cognitive deficits or behavioral impairments and higher levels of neuroinflammation (microglia activation)39-41. This suggests that altered functional connectivity not only mediates cognitive deficits and impairments in behaviors, but that it is also linked to neuroinflammation. In ASD patients, extended microglial activation was suggested to be linked with a loss of connections between different brain areas or to result in functional underconnectivity42. Astrocytes also have been implicated in supporting functional connectivity in the healthy brain while driving abnormal connectivities in neuropsychiatric diseases with chronic neuronal dysfunctions43, 44. To investigate a possible mechanism linking our findings of behavioral alterations and neuroinflammation in the juvenile NHPs that were exposed to anesthesia during infancy, we followed a seed-based approach of rs-fcMRI analysis and found altered brain functional connectivity between the amygdala with other brain areas [primary auditory cortex, the premotor cortex, and the posterior cingulate cortex (PCC)]21. We chose the amygdala as a seed area because it showed robust astrogliosis in the NHPs at this age20. In addition, it is an important hub for the processing of social behaviors which appeared impaired after early-in-life anesthesia exposure as evidenced by the decreased close-social behavior of the NHPs at the same age19. This increased functional connectivity of the amygdala was positively correlated with the increased astrogliosis, suggesting that chronic activation of astrocytes may have contributed to the alterations in functional connectivity of the amygdala and to the behavioral impairments in the juveniles exposed to anesthesia during infancy. Thus, our neuroimaging study in the same cohort of juvenile NHPs provides novel insights to better understand the underlying mechanisms of AIDN by linking neuroinflammation with alterations in brain functional connectivity and behavioral impairments. While, at this point, we do not have direct evidence that the histopathological and neuroimaging changes in NHPs after early-in-life anesthesia exposure lead to the behavioral impairments, studies in rodents provide some evidence that altered astrocytes activity has a causal role in modulating behaviors (recently reviewed in45-47). Depending on the specific brain area, alterations in astrocyte activity have been reported to modulate specific behaviors. For example, optogenetic activation of hippocampal astrocytes altered anxious behavior in mice exposed to an anxiogenic environment48. Another rodent study showed that selective activation of astrocytes  in the striatum resulted in behavioral changes that resemble the symptoms of attention-deficit hyperactivity disorder (ADHD)49. In a rodent model of depression, inhibition of astrocyte activation ameliorated the depression-like behaviors50. In addition, a recent study using an induced pluripotent stem cell (iPSC) approach demonstrated that ASD patient-derived astrocytes when transplanted into the healthy mouse brain induce some of the behavioral impairments associated with ASD, thereby providing evidence for the astrocyte involvement in the etiology of those behaviors51. The amygdala also plays an important role in anxiety, which also is known to be affected by early-in-life anesthesia exposure6, 7, 18. Increased anxiety was found in our cohort of NHPs at the age of 1 year18. However, a relationship between anxiety and alterations in brain functional connectivity (and neuroinflammation) could not be established as the animals were not scanned at this age. Our rs-fcMRI analysis in the 2-year-old NHPs showed altered functional connectivity between the amygdala and the PCC, which itself is involved in social behavior. Therefore, additional analysis using the PCC as seed unsurprisingly detected altered functional connectivities with three other brain areas, and these alterations were correlated with the decreased close-social behavior. Unfortunately, the PCC was not available for our histopathological assessments, so the link between neuroinflammation and functional connectivity alterations in this area needs further investigation.


While we acknowledge that our NHP cohort had a small number of animals per group and we want to be cautious about overinterpreting results, our findings suggest that chronic astroglia activation (neuroinflammation) in the amygdala (and possibly other brain areas) is associated with early-in-life anesthesia exposure and may play a role in the behavioral alterations of juvenile NHPs. In addition, alterations in brain functional connectivity of the amygdala (and possible other brain areas) provide a mechanistic link between neuroinflammation and behavioral alterations. Further studies with larger numbers of NHPs are encouraged to confirm these findings, as well as new studies using  neuroinflammation modulating interventions (e.g., using anti-inflammatory drugs) to establish the causality between the neuroinflammation and the behavioral alterations associated with early-in-life anesthesia exposure. 


The authors exclusively prepared this commentary.

Sources and Funding

No funding was required for this commentary.

Declaration of Conflicting Interests

The authors declare that there is no conflict of interest.

Authorship Statement

VN, JFP-Z and AMB conceptualized the MS. VN and JFP-Z wrote the first MS draft. All authors revised and edited the final MS.


  1. Jevtovic-Todorovic V, Hartman RE, Izumi Y, et al. Early exposure to common anesthetic agents causes widespread neurodegeneration in the developing rat brain and persistent learning deficits. J Neurosci 2003; 23: 876-82.
  2. Brambrink AM, Back SA, Riddle A, et al. Isoflurane-induced apoptosis of oligodendrocytes in the neonatal primate brain. Ann Neurol 2012; 72: 525-35.
  3. Brambrink AM, Evers AS, Avidan MS, et al. Isoflurane-induced neuroapoptosis in the neonatal rhesus macaque brain. Anesthesiology 2010; 112: 834-41.
  4. Creeley C, Dikranian K, Dissen G, et al. Propofol-induced apoptosis of neurones and oligodendrocytes in fetal and neonatal rhesus macaque brain. Br J Anaesth 2013; 110 Suppl 1: i29-38.
  5. Paule MG, Li M, Allen RR, et al. Ketamine anesthesia during the first week of life can cause long-lasting cognitive deficits in rhesus monkeys. Neurotoxicol Teratol 2011; 33: 220-30.
  6. Raper J, Alvarado MC, Murphy KL, et al. Multiple Anesthetic Exposure in Infant Monkeys Alters Emotional Reactivity to an Acute Stressor. Anesthesiology 2015; 123: 1084-92.
  7. Raper J, De Biasio JC, Murphy KL, et al. Persistent alteration in behavioural reactivity to a mild social stressor in rhesus monkeys repeatedly exposed to sevoflurane in infancy. Br J Anaesth 2018; 120: 761-7.
  8. Talpos JC, Chelonis JJ, Li M, et al. Early life exposure to extended general anesthesia with isoflurane and nitrous oxide reduces responsivity on a cognitive test battery in the nonhuman primate. Neurotoxicology 2019; 70: 80-90.
  9. DiMaggio C, Sun LS, Li G. Early childhood exposure to anesthesia and risk of developmental and behavioral disorders in a sibling birth cohort. Anesth Analg 2011; 113: 1143-51.
  10. Flick RP, Katusic SK, Colligan RC, et al. Cognitive and behavioral outcomes after early exposure to anesthesia and surgery. Pediatrics 2011; 128: e1053-61.
  11. Glatz P, Sandin RH, Pedersen NL, et al. Association of Anesthesia and Surgery During Childhood With Long-term Academic Performance. JAMA Pediatr 2017; 171: e163470.
  12. Ing C, DiMaggio C, Whitehouse A, et al. Long-term differences in language and cognitive function after childhood exposure to anesthesia. Pediatrics 2012; 130: e476-85.
  13. Wilder RT, Flick RP, Sprung J, et al. Early exposure to anesthesia and learning disabilities in a population-based birth cohort. Anesthesiology 2009; 110: 796-804.
  14. McCann ME, de Graaff JC, Dorris L, et al. Neurodevelopmental outcome at 5 years of age after general anaesthesia or awake-regional anaesthesia in infancy (GAS): an international, multicentre, randomised, controlled equivalence trial. Lancet 2019; 393: 664-77.
  15. Sun LS, Li G, Miller TL, et al. Association Between a Single General Anesthesia Exposure Before Age 36 Months and Neurocognitive Outcomes in Later Childhood. JAMA 2016; 315: 2312-20
  16. Warner DO, Zaccariello MJ, Katusic SK, et al. Neuropsychological and Behavioral Outcomes after Exposure of Young Children to Procedures Requiring General Anesthesia: The Mayo Anesthesia Safety in Kids (MASK) Study. Anesthesiology 2018; 129: 89-105.
  17. Ing C, Jackson WM, Zaccariello MJ, et al. Prospectively assessed neurodevelopmental outcomes in studies of anaesthetic neurotoxicity in children: a systematic review and meta-analysis. Br J Anaesth 2021; 126: 433-44.
  18. Coleman K, Robertson ND, Dissen GA, et al. Isoflurane Anesthesia Has Long-term Consequences on Motor and Behavioral Development in Infant Rhesus Macaques. Anesthesiology 2017; 126: 74-84.
  19. Neudecker V, Perez-Zoghbi JF, Coleman K, et al. Infant isoflurane exposure affects social behaviours, but does not impair specific cognitive domains in juvenile non-human primates. Br J Anaesth 2020.
  20. Neudecker V, Perez-Zoghbi JF, Martin LD, et al. Astrogliosis in juvenile non-human primates 2 years after infant anaesthesia exposure. Br J Anaesth 2021; 127: 447-57.
  21. Neudecker V, Perez-Zoghbi JF, Miranda-Domínguez O, et al. Early-in-life isoflurane exposure alters resting-state functional connectivity in juvenile non-human primates. Br J Anaesth 2023.
  22. Lyman M, Lloyd DG, Ji X, et al. Neuroinflammation: the role and consequences. Neurosci Res 2014; 79: 1-12.
  23. Xiong Y, Chen J, Li Y. Microglia and astrocytes underlie neuroinflammation and synaptic susceptibility in autism spectrum disorder. Front Neurosci 2023; 17: 1125428.
  24. Dai J, Li X, Wang C, et al. Repeated neonatal sevoflurane induced neurocognitive impairment through NF-kappaB-mediated pyroptosis. J Neuroinflammation 2021; 18: 180.
  25. Ji MH, Qiu LL, Yang JJ, et al. Pre-administration of curcumin prevents neonatal sevoflurane exposure-induced neurobehavioral abnormalities in mice. Neurotoxicology 2015; 46: 155-64.
  26. Pang X, Zhang P, Zhou Y, et al. Dexmedetomidine pretreatment attenuates isoflurane-induced neurotoxicity via inhibiting the TLR2/NF-kappaB signaling pathway in neonatal rats. Exp Mol Pathol 2020; 112: 104328.
  27. Shen X, Dong Y, Xu Z, et al. Selective anesthesia-induced neuroinflammation in developing mouse brain and cognitive impairment. Anesthesiology 2013; 118: 502-15.
  28. Shi Y, Wang G, Li J, et al. Hydrogen gas attenuates sevoflurane neurotoxicity through inhibiting nuclear factor kappa-light-chain-enhancer of activated B cells signaling and proinflammatory cytokine release in neonatal rats. Neuroreport 2017; 28: 1170-5.
  29. Wang Y, Wang C, Zhang Y, et al. Pre-administration of luteoline attenuates neonatal sevoflurane-induced neurotoxicity in mice. Acta Histochem 2019; 121: 500-7.
  30. Wu N, Liu H, Lv X, et al. Neobaicalein prevents isoflurane anesthesia-induced cognitive impairment in neonatal mice via regulating CREB1. Clinics (Sao Paulo) 2023; 78: 100201.
  31. Broad KD, Hassell J, Fleiss B, et al. Isoflurane Exposure Induces Cell Death, Microglial Activation and Modifies the Expression of Genes Supporting Neurodevelopment and Cognitive Function in the Male Newborn Piglet Brain. PLoS One 2016; 11: e0166784.
  32. Tao G, Zhang J, Zhang L, et al. Sevoflurane induces tau phosphorylation and glycogen synthase kinase 3beta activation in young mice. Anesthesiology 2014; 121: 510-27.
  33. Zhang J, Dong Y, Lining H, et al. Interaction of Tau, IL-6 and mitochondria on synapse and cognition following sevoflurane anesthesia in young mice. Brain Behav Immun Health 2020; 8: 100133.
  34. Hogarth K, Vanama RB, Stratmann G, et al. Singular and short-term anesthesia exposure in the developing brain induces persistent neuronal changes consistent with chronic neurodegenerative disease. Sci Rep 2021; 11: 5673.
  35. Wang F, Li C, Shao J, et al. Sevoflurane induces inflammation of microglia in hippocampus of neonatal rats by inhibiting Wnt/beta-Catenin/CaMKIV pathway. J Pharmacol Sci 2021; 146: 105-15.
  36. Hirotsu A, Iwata Y, Tatsumi K, et al. Maternal exposure to volatile anesthetics induces IL-6 in fetal brains and affects neuronal development. Eur J Pharmacol 2019; 863: 172682.
  37. Zheng H, Dong Y, Xu Z, et al. Sevoflurane anesthesia in pregnant mice induces neurotoxicity in fetal and offspring mice. Anesthesiology 2013; 118: 516-26.
  38. Zhang X, Liu S, Newport GD, et al. In Vivo Monitoring of Sevoflurane-induced Adverse Effects in Neonatal Nonhuman Primates Using Small-animal Positron Emission Tomography. Anesthesiology 2016; 125: 133-46.
  39. Nagai Y, Kirino E, Tanaka S, et al. Functional connectivity in autism spectrum disorder evaluated using rs-fMRI and DKI. Cereb Cortex 2023.
  40. Passamonti L, Tsvetanov KA, Jones PS, et al. Neuroinflammation and Functional Connectivity in Alzheimer's Disease: Interactive Influences on Cognitive Performance. J Neurosci 2019; 39: 7218-26.
  41. Rauchmann BS, Brendel M, Franzmeier N, et al. Microglial Activation and Connectivity in Alzheimer Disease and Aging. Ann Neurol 2022; 92: 768-81.
  42. Rodriguez JI, Kern JK. Evidence of microglial activation in autism and its possible role in brain underconnectivity. Neuron Glia Biol 2011; 7: 205-13.
  43. Liu J, Mo JW, Wang X, et al. Astrocyte dysfunction drives abnormal resting-state functional connectivity in depression. Sci Adv 2022; 8: eabo2098.
  44. Shah D, Gsell W, Wahis J, et al. Astrocyte calcium dysfunction causes early network hyperactivity in Alzheimer's disease. Cell Rep 2022; 40: 111280.
  45. Brazhe A, Verisokin A, Verveyko D, et al. Astrocytes: new evidence, new models, new roles. Biophys Rev 2023; 15: 1303-33
  46. Lyon KA, Allen NJ. From Synapses to Circuits, Astrocytes Regulate Behavior. Front Neural Circuits 2021; 15: 786293
  47. Oliveira JF, Sardinha VM, Guerra-Gomes S, et al. Do stars govern our actions? Astrocyte involvement in rodent behavior. Trends Neurosci 2015; 38: 535-49
  48. Cho WH, Noh K, Lee BH, et al. Hippocampal astrocytes modulate anxiety-like behavior. Nat Commun 2022; 13: 6536
  49. Nagai J, Rajbhandari AK, Gangwani MR, et al. Hyperactivity with Disrupted Attention by Activation of an Astrocyte Synaptogenic Cue. Cell 2019; 177: 1280-92 e20
  50. Wang Y, Ni J, Zhai L, et al. Inhibition of activated astrocyte ameliorates lipopolysaccharide- induced depressive-like behaviors. J Affect Disord 2019; 242: 52-9
  51. Allen M, Huang BS, Notaras MJ, et al. Astrocytes derived from ASD individuals alter behavior and destabilize neuronal activity through aberrant Ca(2+) signaling. Mol Psychiatry 2022; 27: 2470-84

Article Info

Article Notes

  • Published on: May 17, 2024


  • Neuroinflammation
  • astrogliosis
  • neurodevelopment
  • non-human primates
  • brain functional connectivity
  • anesthesia-induced developmental neurotoxicity


Dr. Ansgar M. Brambrink,
Department of Anesthesiology, Columbia University Medical Center, New York, NY 10032, USA.;

Copyright: ©2024 Brambrink AM. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License.