Newly Published
Perioperative Medicine  |   May 2020
Isoflurane Exposure in Juvenile Caenorhabditis elegans Causes Persistent Changes in Neuron Dynamics
Author Notes
  • From the Department of Physiology and Biophysics, Boston University School of Medicine, Boston, Massachusetts (G.S.W., C.V.G., C.W.C.); and the Department of Anesthesiology, Perioperative and Pain Medicine, Brigham and Women’s Hospital, Boston, Massachusetts (C.W.C.).
  • Part of the work presented in this article has been presented at the Post Graduate Assembly in Anesthesiology (PGA72) in New York, New York, December 7–11, 2018.
    Part of the work presented in this article has been presented at the Post Graduate Assembly in Anesthesiology (PGA72) in New York, New York, December 7–11, 2018.×
  • Submitted for publication December 10, 2019. Accepted for publication April 2, 2020.
    Submitted for publication December 10, 2019. Accepted for publication April 2, 2020.×
  • Correspondence: Address correspondence to Dr. Connor: Brigham and Women’s Hospital, 75 Francis Street, CWN L1, Boston, Massachusetts 02115. cconnor@bwh.harvard.edu. Information on purchasing reprints may be found at www.anesthesiology.org or on the masthead page at the beginning of this issue. Anesthesiology’s articles are made freely accessible to all readers, for personal use only, 6 months from the cover date of the issue.
Article Information
Perioperative Medicine / Pharmacology
Perioperative Medicine   |   May 2020
Isoflurane Exposure in Juvenile Caenorhabditis elegans Causes Persistent Changes in Neuron Dynamics
Anesthesiology Newly Published on May 21, 2020. doi:https://doi.org/10.1097/ALN.0000000000003335
Anesthesiology Newly Published on May 21, 2020. doi:https://doi.org/10.1097/ALN.0000000000003335
Abstract

Background: Animal studies demonstrate that anesthetic exposure during neurodevelopment can lead to persistent behavioral impairment. The changes in neuronal function underlying these effects are incompletely understood. Caenorhabditis elegans is well suited for functional imaging of postanesthetic effects on neuronal activity. This study aimed to examine such effects within the neurocircuitry underlying C. elegans locomotion.

Methods: C. elegans were exposed to 8% isoflurane for 3 h during the neurodevelopmentally critical L1 larval stage. Locomotion was assessed during early and late adulthood. Spontaneous activity was measured within the locomotion command interneuron circuitry using confocal and light-sheet microscopy of the calcium-sensitive fluorophore GCaMP6s.

Results: C. elegans exposed to isoflurane demonstrated attenuation in spontaneous reversal behavior, persisting throughout the animal’s lifespan (reversals/min: untreated early adulthood, 1.14 ± 0.42, vs. isoflurane-exposed early adulthood, 0.83 ± 0.55; untreated late adulthood, 1.75 ± 0.64, vs. isoflurane-exposed late adulthood, 1.14 ± 0.68; P = 0.001 and 0.006, respectively; n > 50 animal tracks/condition). Likewise, isoflurane exposure altered activity dynamics in the command interneuron AVA, which mediates crawling reversals. The rate at which AVA transitions between activity states was found to be increased. These anesthetic-induced effects were more pronounced with age (off-to-on activity state transition time (s): untreated early adulthood, 2.5 ± 1.2, vs. isoflurane-exposed early adulthood, 1.9 ± 1.3; untreated late adulthood, 4.6 ± 3.0, vs. isoflurane-exposed late adulthood, 3.0 ± 2.4; P = 0.028 and 0.008, respectively; n > 35 traces acquired from more than 15 animals/condition). Comparable effects were observed throughout the command interneuron circuitry, indicating that isoflurane exposure alters transition rates between behavioral crawling states of the system overall. These effects were modulated by loss-of-function mutations within the FoxO transcription factor daf-16 and by rapamycin-mediated mechanistic Target of Rapamycin (mTOR) inhibition.

Conclusions: Altered locomotive behavior and activity dynamics indicate a persistent effect on interneuron dynamics and circuit function in C. elegans after developmental exposure to isoflurane. These effects are modulated by a loss of daf-16 or mTOR activity, consistent with a pathologic activation of stress-response pathways.

Editor’s Perspective:

What We Already Know about This Topic:

  • Experimental data in laboratory animals demonstrate that early life exposure to anesthetics can induce lasting neurobehavioral and cognitive alterations

  • The neurobiological bases of these alterations are incompletely understood

  • Caenorhabditis elegans is a well suited experimental model for long-term functional imaging of neurons after anesthesia exposure

What This Article Tells Us That Is New:

  • Exposure of Caenorhabditis elegans to isoflurane for 3 h during the first larval stage results in lifelong attenuation in spontaneous crawling reversal behavior

  • These effects correlate with persistently altered activity dynamics of command interneurons mediating crawling reversals

  • Genetic dissection of potential underlying mechanisms reveals that these effects are modulated by a loss of daf-16 or mechanistic Target of Rapamycin (mTOR) activity, consistent with a persistent pathologic activation of stress-response pathways