Neurotransmitter networks in mouse prefrontal cortex are reconfigured by isoflurane anesthesia

Abstract

This study quantified eight, small molecule neurotransmitters collected simultaneously from prefrontal cortex of C57BL/6J mouse (n=23) during wakefulness and during isoflurane anesthesia (1.3%). Using isoflurane anesthesia as an independent variable enabled evaluation of the hypothesis that isoflurane anesthesia differentially alters concentrations of multiple neurotransmitters and their interactions. Machine learning was applied to reveal higher order interactions among neurotransmitters. Using a between-subjects design, microdialysis was performed during wakefulness and during anesthesia. Concentrations (nM) of acetylcholine, adenosine, dopamine, GABA, glutamate, histamine, norepinephrine, and serotonin in the dialysis samples are reported (mean ± SD). Relative to wakefulness, acetylcholine concentration was lower during isoflurane anesthesia (1.254 ± 1.118 versus 0.401 ± 0.134, P=0.009), and concentrations of adenosine (29.456 ± 29.756 versus 101.321 ± 38.603, P<0.001), dopamine (0.0578 ± 0.0384 versus 0.113 ± 0.084, P=0.036), and norepinephrine (0.126 ± 0.080 versus 0.219 ± 0.066, P=0.010) were higher during anesthesia. Isoflurane reconfigured neurotransmitter interactions in prefrontal cortex, and the state of isoflurane anesthesia was reliably predicted by prefrontal cortex concentrations of adenosine, norepinephrine, and acetylcholine. A novel finding to emerge from machine learning analyses is that neurotransmitter concentration profiles in mouse prefrontal cortex undergo functional reconfiguration during isoflurane anesthesia. Adenosine, norepinephrine, and acetylcholine showed high feature importance, supporting the interpretation that interactions among these three transmitters may play a key role in modulating levels of cortical and behavioral arousal.

Isoflurane anesthesia disrupts the cortical metabolome

“…5 and Supplemental Table S1). This finding is consistent with recent evidence that one of the major predictors of isoflurane anesthesia was adenosine concentration in mouse PFC ( Zhang et al 2020 ). Meta-analyses indicate that all types of anesthesia increase adenosine ( van der Mierden et al 2018 ).…”

“…Microdialysis sample collection typically reveals time-dependent changes in levels of analytes that we have shown may vary by molecule ( Zhang et al 2020 ) and brain region ( Van Dort et al 2009 ). For both the wakefulness and anesthesia conditions, all microdialysis samples were collected between 10:00 AM and 2:00 PM.…”

“…000664; n = 24) were purchased from the Jackson Laboratory (Bar Harbor, ME). These mice comprised a different group from those used for previous studies of the PFC metabolome during sleep and wakefulness ( Bourdon et al 2018 ) and from those used for quantification of PFC neurotransmitters during isoflurane anesthesia ( Zhang et al 2020 ). Throughout the study, mice had ad libitum access to food (Teklad 8640) and water.…”

“…The stereotaxic aim point was 2.6 mm anterior, 1 mm lateral to the midline, and 1 mm ventral, relative to bregma ( Franklin and Paxinos 2008 ). As described previously ( Zhang et al 2020 ), mice were anesthetized with isoflurane, and an implanted guide tube was secured to the skull with dental acrylic. Mice recovered from the surgery for 1 wk and then were acclimated to being handled and to being placed in an open glass recording chamber.…”

“…The results reveal more differences than similarities between the PFC metabolome during anesthesia and sleep ( Bourdon et al 2018 ). During isoflurane anesthesia, the PFC metabolome differed significantly from the waking metabolome for neurotransmitter precursors that regulate point-to-point chemical transmission ( Zhang et al 2020 ) and for molecules that modulate volume transmission ( Marcoli et al 2015 ). The results provide novel comparisons of metabolites and their biofunction during the loss of wakefulness caused by sleep ( Bourdon et al 2018 ) and by isoflurane anesthesia.…”