Research ArticleNEUROPHYSIOLOGY

Increased glymphatic influx is correlated with high EEG delta power and low heart rate in mice under anesthesia

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Science Advances  27 Feb 2019:
Vol. 5, no. 2, eaav5447
DOI: 10.1126/sciadv.aav5447
  • Fig. 1 Anesthetic regimen effects CSF tracer distribution at the dorsal and ventral brain surfaces.

    (A) Population-based average of tracer distribution at the dorsal (top) and ventral (bottom) brain surfaces with anatomical references. (B) Comparison of average tracer distribution at the dorsal (top) and ventral (bottom) brain surfaces in the six groups of anesthetized mice. (C) Boxplots comparing dorsal (top) and ventral (bottom) tracer distributions for the six different anesthetic agents or combinations (whiskers, minimum and maximum; box, quartiles; and line, median). Kruskal-Wallis test followed by Bonferroni correction, *P < 0.05, **P < 0.01, ***P < 0.001. K/X, n = 35 animals; ISO supplemented with dex (ISO/dex), n = 14 animals; pentobarbital (Pentobar), n = 27 animals; α-chloralose (α-chlor), n = 20 animals; tribromoethanol (Avertin), n = 27 animals; and ISO, n = 20 animals. ACA, anterior cerebral artery; BA, basilar artery; C. Willis, circle of Willis; ICA, internal carotid artery; MCA, middle cerebral artery; PCA, posterior cerebral artery; RCS, rostral confluence of sinuses; SS, sigmoid sinus; SSS, superior sagittal sinus; and TS, transverse sinus. a.u., arbitrary units.

  • Fig. 2 Anesthetic agents differentially alter CSF tracer distribution in coronal brain sections.

    (A) Population-based median tracer distribution within the most posterior slice position in the six groups of anesthetized mice. (B) Boxplot displaying average tracer distribution across all brain slices (each dot represents the average of one brain) in the six groups of anesthetized mice (whiskers, minimum and maximum; box, quartiles; and line, median). Kruskal-Wallis test followed by Bonferroni correction, *P < 0.05, ***P < 0.001. (C and D) Correlation between CSF tracer distribution in coronal slices (slice MPI) and tracer distribution at the (C) ventral and (D) dorsal surfaces. K/X, n = 36 animals; ISO supplemented with dex, n = 14 animals; pentobarbital, n = 27 animals; α-chloralose, n = 20 animals; tribromoethanol, n = 27 animals; and ISO, n = 22 animals.

  • Fig. 3 Glymphatic tracer influx correlates with the prevalence of slow delta waves.

    (A) Representative normalized EEG power spectra for each anesthetic regimen. (B to E) Scatterplots depicting the correlation between MPI in coronal slices and the prevalence of delta (B), beta (C), theta (D), and alpha (E) EEG band power. Each dot represents the group mean (whiskers, SD). Correlations were calculated using group means; P values and R2 values are displayed for each correlation. K/X, n = 36 animals for influx and 8 animals for EEG; ISO supplemented with dex, n = 14 animals for influx and 7 animals for EEG; pentobarbital, n = 27 animals for influx and 8 animals for EEG; α-chloralose, n = 20 animals for influx and 8 animals for EEG; tribromoethanol, n = 27 animals for influx and 5 animals for EEG; and ISO, n = 23 animals for influx and 6 animals for EEG.

  • Fig. 4 Glymphatic tracer influx is inversely correlated with heart rate.

    (A) Representative traces of electrocardiogram and respiratory measurements for the six anesthetic regimens. (B to D) Scatterplots showing the correlation between MPI in coronal slices and heart rate (B), respiratory rate (C), and systolic blood pressure (BP) (D) across all anesthetic groups. Each dot represents the group mean (whiskers, SD). Correlations were calculated using group means; P values and R2 values are displayed for each correlation. K/X, n = 36 animals for influx and 9 animals for cardiopulmonary measurements; ISO supplemented with dex, n = 14 animals for influx and 7 animals for cardiopulmonary measurements (CPMs); pentobarbital, n = 27 animals for influx and 8 animals for CPMs; tribromoethanol, n = 27 animals for influx and 5 animals for CPMs; α-chloralose, n = 20 animals for influx and 8 animals for CPMs; and ISO, n = 23 animals for influx and 7 animals for CPMs.

  • Table 1 Drug mechanism(s) of action.

    This table provides a summary of how different drugs used in this study modulate neurotransmission. The drug name is listed on the left, potential targets of each drug are listed in the middle, and references for more in-depth descriptions are provided on the right. NMDAR, N-methyl-d-aspartate receptor; 5-HT, 5-hydroxytryptamine; K2P, two-pore potassium; HCN, hyperpolarization-activated cyclic nucleotide-gated.

    DrugMechanism of actionReferences
    KetamineNMDAR antagonist(32, 33)
    Xylazineα2-Adrenergic
    receptor agonist
    (32, 34, 35)
    PentobarbitalPositive allosteric
    modulator of GABAA
    chloride channels
    (32, 36)
    α-ChloralosePositive allosteric
    modulator of GABAA
    chloride channels
    (32, 37, 38)
    Avertin(2,2,2-
    tribromoethanol)
    Unclear. Potential:
    agonist for GABAA
    and glycine receptors,
    negative allosteric
    modulator for
    dopaminergic, 5-HT,
    opioid, muscarinic,
    and adrenergic
    receptors
    (32, 37)
    IsofluranePositive allosteric
    modulator of GABAA
    chloride channels;
    NMDAR, K2P channel,
    and HCN channel
    antagonist
    (37, 39, 40)
    DexmedetomidineMore potent and
    more selective
    α2-adrenergic
    receptor agonist than
    xylazine
    (32, 35)

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/2/eaav5447/DC1

    Fig. S1. Index of sections from each anesthetic group.

    Fig. S2. Subregion analysis of glymphatic influx in coronal slices.

    Fig. S3. Analysis of interior brain slices under anesthesia.

    Fig. S4. Two hours of ISO do not improve glymphatic influx.

    Fig. S5. Comparisons of EEG power spectrum prevalence across anesthetic regimens.

    Fig. S6. Comparison of intracranial pressure across anesthetic regimens.

    Fig. S7. Comparisons of cardiovascular measurements across anesthetic regimens.

    Table S1. Statistical comparison of parameters between anesthetic regimens.

  • Supplementary Materials

    This PDF file includes:

    • Fig. S1. Index of sections from each anesthetic group.
    • Fig. S2. Subregion analysis of glymphatic influx in coronal slices.
    • Fig. S3. Analysis of interior brain slices under anesthesia.
    • Fig. S4. Two hours of ISO do not improve glymphatic influx.
    • Fig. S5. Comparisons of EEG power spectrum prevalence across anesthetic regimens.
    • Fig. S6. Comparison of intracranial pressure across anesthetic regimens.
    • Fig. S7. Comparisons of cardiovascular measurements across anesthetic regimens.
    • Table S1. Statistical comparison of parameters between anesthetic regimens.

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