Water diffusion closely reveals neural activity status in rat brain loci affected by anesthesia

Diffusion functional MRI (DfMRI) reveals neuronal activation even when neurovascular coupling is abolished, contrary to blood oxygenation level—dependent (BOLD) functional MRI (fMRI). Here, we show that the water apparent diffusion coefficient (ADC) derived from DfMRI increased in specific rat brain regions under anesthetic conditions, reflecting the decreased neuronal activity observed with local field potentials (LFPs), especially in regions involved in wakefulness. In contrast, BOLD signals showed nonspecific changes, reflecting systemic effects of the anesthesia on overall brain hemodynamics status. Electrical stimulation of the central medial thalamus nucleus (CM) exhibiting this anesthesia-induced ADC increase led the animals to transiently wake up. Infusion in the CM of furosemide, a specific neuronal swelling blocker, led the ADC to increase further locally, although LFP activity remained unchanged, and increased the current threshold awakening the animals under CM electrical stimulation. Oppositely, induction of cell swelling in the CM through infusion of a hypotonic solution (−80 milliosmole [mOsm] artificial cerebrospinal fluid [aCSF]) led to a local ADC decrease and a lower current threshold to wake up the animals. Strikingly, the local ADC changes produced by blocking or enhancing cell swelling in the CM were also mirrored remotely in areas functionally connected to the CM, such as the cingulate and somatosensory cortex. Together, those results strongly suggest that neuronal swelling is a significant mechanism underlying DfMRI.

[1]  K. S. Olsen,et al.  Effect of 1 or 2 MAC isoflurane with or without ketanserin on cerebral blood flow autoregulation in man. , 1994, British journal of anaesthesia.

[2]  A. L. Goldin,et al.  Shaker-Related Potassium Channels in the Central Medial Nucleus of the Thalamus Are Important Molecular Targets for Arousal Suppression by Volatile General Anesthetics , 2013, The Journal of Neuroscience.

[3]  P. Schwartzkroin,et al.  Osmolarity, ionic flux, and changes in brain excitability , 1998, Epilepsy Research.

[4]  L. Vargova,et al.  Dynamic changes in water ADC, energy metabolism, extracellular space volume, and tortuosity in neonatal rat brain during global ischemia , 1996, Magnetic resonance in medicine.

[5]  A. R. Gardner-Medwin,et al.  Apparent diffusion coefficient and MR relaxation during osmotic manipulation in isolated turtle cerebellum , 2000, Magnetic resonance in medicine.

[6]  M. Witter,et al.  The intralaminar and midline nuclei of the thalamus. Anatomical and functional evidence for participation in processes of arousal and awareness , 2002, Brain Research Reviews.

[7]  D A Turner,et al.  Use of intrinsic optical signals to monitor physiological changes in brain tissue slices. , 1999, Methods.

[8]  Edward J. Auerbach,et al.  Dose-dependent effect of isoflurane on regional cerebral blood flow in anesthetized macaque monkeys , 2013, Neuroscience Letters.

[9]  Il-Sung Jang,et al.  alpha 2-Adrenoceptor-mediated presynaptic modulation of GABAergic transmission in mechanically dissociated rat ventrolateral preoptic neurons. , 2003, Journal of neurophysiology.

[10]  Alexander S. Tolpygo,et al.  Frequency-selective control of cortical and subcortical networks by central thalamus , 2015, eLife.

[11]  Ichiji Tasaki,et al.  Rapid swelling of neurons during synaptic transmission in the bullfrog sympathetic ganglion , 1985, Brain Research.

[12]  R. McCarley,et al.  Control of sleep and wakefulness. , 2012, Physiological reviews.

[13]  J DeFelipe,et al.  Estimation of the number of synapses in the cerebral cortex: methodological considerations. , 1999, Cerebral cortex.

[14]  C. Vahle-hinz,et al.  What can in vivo electrophysiology in animal models tell us about mechanisms of anaesthesia? , 2002, British journal of anaesthesia.

[15]  R. Keynes,et al.  Evidence for structural changes during the action potential in nerves from the walking legs of Maia squinado. , 1968, The Journal of physiology.

[16]  D. Tank,et al.  Brain magnetic resonance imaging with contrast dependent on blood oxygenation. , 1990, Proceedings of the National Academy of Sciences of the United States of America.

[17]  B. MacVicar,et al.  Imaging cell volume changes and neuronal excitation in the hippocampal slice , 1994, Neuroscience.

[18]  P. Schwartzkroin,et al.  Dissociation of Synchronization and Excitability in Furosemide Blockade of Epileptiform Activity , 1995, Science.

[19]  Alan Carleton,et al.  Sensory-Evoked Intrinsic Imaging Signals in the Olfactory Bulb Are Independent of Neurovascular Coupling , 2015, Cell reports.

[20]  Denis Le Bihan,et al.  The ‘wet mind’: water and functional neuroimaging , 2007 .

[21]  Angus M. Brown,et al.  Intrinsic optical signals in the rat optic nerve: Role for K+ uptake via NKCC1 and swelling of astrocytes , 2002, Glia.

[22]  G. Palm,et al.  Density of neurons and synapses in the cerebral cortex of the mouse , 1989, The Journal of comparative neurology.

[23]  D. Le Bihan.  Apparent diffusion coefficient and beyond: what diffusion MR imaging can tell us about tissue structure. , 2013, Radiology.

[24]  K. Holthoff,et al.  Directed spatial potassium redistribution in rat neocortex , 2000, Glia.

[25]  C. Nicholson,et al.  Changes in brain cell shape create residual extracellular space volume and explain tortuosity behavior during osmotic challenge. , 2000, Proceedings of the National Academy of Sciences of the United States of America.

[26]  D. Le Bihan.  The ‘wet mind’: water and functional neuroimaging , 2007, Physics in medicine and biology.

[27]  K Murase,et al.  Slow intrinsic optical signals in the rat spinal dorsal horn in slice , 1998, Neuroreport.

[28]  Y. Okada,et al.  Volume‐sensitive chloride channels in mouse cortical neurons: characterization and role in volume regulation , 2005, The European journal of neuroscience.

[29]  J. A. Payne,et al.  The Neuron-specific K-Cl Cotransporter, KCC2 , 1999, The Journal of Biological Chemistry.

[30]  R. Keynes,et al.  Light Scattering and Birefringence Changes during Nerve Activity , 1968, Nature.

[31]  N. Logothetis,et al.  Negative functional MRI response correlates with decreases in neuronal activity in monkey visual area V1 , 2006, Nature Neuroscience.

[32]  Eva Syková,et al.  Glial swelling and astrogliosis produce diffusion barriers in the rat spinal cord , 1999, Glia.

[33]  Cohen Lb,et al.  Evidence for structural changes during the action potential in nerves from the walking legs of Maia squinado. , 1968 .

[34]  S. Kirov,et al.  Physiological evidence that pyramidal neurons lack functional water channels. , 2006, Cerebral cortex.

[35]  Bharat B. Biswal,et al.  A protocol for use of medetomidine anesthesia in rats for extended studies using task-induced BOLD contrast and resting-state functional connectivity , 2009, NeuroImage.

[36]  L. Héja,et al.  Neuronal and Astroglial Correlates Underlying Spatiotemporal Intrinsic Optical Signal in the Rat Hippocampal Slice , 2013, PloS one.

[37]  I. Tasaki,et al.  The origin of rapid changes in birefringence, light scattering and dye absorbance associated with excitation of nerve fibers. , 1993, The Japanese journal of physiology.

[38]  M. Verhoye,et al.  The power of using functional fMRI on small rodents to study brain pharmacology and disease , 2015, Front. Pharmacol..

[39]  B. MacVicar,et al.  Imaging of synaptically evoked intrinsic optical signals in hippocampal slices , 1991, The Journal of neuroscience : the official journal of the Society for Neuroscience.

[40]  Kai-Hsiang Chuang,et al.  Neural correlate of resting-state functional connectivity under α2 adrenergic receptor agonist, medetomidine , 2014, NeuroImage.

[41]  J. Ferrendelli,et al.  Characterization of gabaergic seizure regulation in the midline thalamus , 1990, Neuropharmacology.

[42]  Hiroshi Tsubokawa,et al.  GABAergic input contributes to activity-dependent change in cell volume in the hippocampal CA1 region , 2002, Neuroscience Research.

[43]  K. Holthoff,et al.  Intrinsic optical signals in rat neocortical slices measured with near- infrared dark-field microscopy reveal changes in extracellular space , 1996, The Journal of neuroscience : the official journal of the Society for Neuroscience.

[44]  D. Le Bihan,et al.  Water diffusion in brain cortex closely tracks underlying neuronal activity , 2013, Proceedings of the National Academy of Sciences.

[45]  D. Le Bihan,et al.  Direct and fast detection of neuronal activation in the human brain with diffusion MRI. , 2006, Proceedings of the National Academy of Sciences of the United States of America.

[46]  C. Humpel,et al.  ORGANOTYPIC BRAIN SLICE CULTURES: A REVIEW , 2015, Neuroscience.

[47]  D L Buckley,et al.  The effect of ouabain on water diffusion in the rat hippocampal slice measured by high resolution NMR imaging , 1999, Magnetic resonance in medicine.

[48]  K van Ackern,et al.  Local Cerebral Blood Flow, Local Cerebral Glucose Utilization, and Flow‐Metabolism Coupling during Sevoflurane versus Isoflurane Anesthesia in Rats , 1998, Anesthesiology.

[49]  P. Kara,et al.  Neural correlates of single vessel hemodynamic responses in vivo , 2016, Nature.

[50]  B W Connors,et al.  Activity-dependent shrinkage of extracellular space in rat optic nerve: a developmental study , 1985, The Journal of neuroscience : the official journal of the Society for Neuroscience.

[51]  N. Logothetis,et al.  Neurophysiological investigation of the basis of the fMRI signal , 2001, Nature.

[52]  D. Bihan.  Apparent Diffusion Coefficient and Beyond: What Diffusion MR Imaging Can Tell Us about Tissue Structure , 2013 .

[53]  Hidenao Fukuyama,et al.  An intrinsic diffusion response function for analyzing diffusion functional MRI time series , 2009, NeuroImage.

[54]  Pierre Marquet,et al.  Effects of hypotonic stress and ouabain on the apparent diffusion coefficient of water at cellular and tissue levels in Aplysia , 2014, NMR in biomedicine.

[55]  R. David Andrew,et al.  Evidence against Volume Regulation by Cortical Brain Cells during Acute Osmotic Stress , 1997, Experimental Neurology.

[56]  Jeremy J. Flint,et al.  Diffusion weighted magnetic resonance imaging of neuronal activity in the hippocampal slice model , 2009, NeuroImage.

[57]  Amy Brodtmann,et al.  Beyond BOLD: Optimizing functional imaging in stroke populations , 2015, Human brain mapping.

[58]  T. Duong,et al.  Regional Cerebral Blood Flow and BOLD Responses in Conscious and Anesthetized Rats under Basal and Hypercapnic Conditions: Implications for Functional MRI Studies , 2003, Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism.

[59]  Dae-Shik Kim,et al.  Origin of Negative Blood Oxygenation Level—Dependent fMRI Signals , 2002, Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism.

[60]  Denis Le Bihan,et al.  Diffusion MRI: what water tells us about the brain , 2014, EMBO molecular medicine.

[61]  I. Tasaki,et al.  Mechanical changes associated with synaptic transmission in the mammalian superior cervical ganglion , 1990, Journal of neuroscience research.

[62]  Dietmar Plenz,et al.  Assessing the sensitivity of diffusion MRI to detect neuronal activity directly , 2016, Proceedings of the National Academy of Sciences.

[63]  L. Swanson.  The Rat Brain in Stereotaxic Coordinates, George Paxinos, Charles Watson (Eds.). Academic Press, San Diego, CA (1982), vii + 153, $35.00, ISBN: 0 125 47620 5 , 1984 .

[64]  Karla L Miller,et al.  Evidence for a vascular contribution to diffusion FMRI at high b value , 2007, Proceedings of the National Academy of Sciences.

[65]  D. Le Bihan,et al.  Clinical Intravoxel Incoherent Motion and Diffusion MR Imaging: Past, Present, and Future. , 2016, Radiology.

[66]  C. Saper,et al.  Sleep State Switching , 2010, Neuron.

[67]  R. Fremeau,et al.  EXPRESSION OF α2-ADRENERGIC RECEPTOR SUBTYPES IN THE MOUSE BRAIN: EVALUATION OF SPATIAL AND TEMPORAL INFORMATION IMPARTED BY 3 kb OF 5′ REGULATORY SEQUENCE FOR THE α2A AR-RECEPTOR GENE IN TRANSGENIC ANIMALS , 1996, Neuroscience.

[68]  Denis Le Bihan,et al.  Diffusion Magnetic Resonance Imaging: What Water Tells Us about Biological Tissues , 2015, PLoS biology.

[69]  I. Tasaki,et al.  Rapid structural changes in nerve fibers and cells associated with their excitation processes. , 1999, The Japanese journal of physiology.

[70]  Essa Yacoub,et al.  Decreases in ADC observed in tissue areas during activation in the cat visual cortex at 9.4 T using high diffusion sensitization. , 2008, Magnetic resonance imaging.

[71]  I. Tasaki,et al.  Optical changes during nerve excitation: interpretation on the basis of rapid structural changes in the superficial gel layer of nerve fibers. , 1994, Physiological chemistry and physics and medical NMR.

[72]  V. Skrebitsky,et al.  Mechanisms of GABAA receptor blockade by millimolar concentrations of furosemide in isolated rat Purkinje cells , 2002, Neuropharmacology.

[73]  J. Gore,et al.  Changes in water diffusion and relaxation properties of rat cerebrum during status epilepticus , 1993, Magnetic resonance in medicine.

[74]  Tao Jin,et al.  Functional changes of apparent diffusion coefficient during visual stimulation investigated by diffusion-weighted gradient-echo fMRI , 2008, NeuroImage.

[75]  T. Tsurugizawa,et al.  Distinct effects of isoflurane on basal BOLD signals in tissue/vascular microstructures in rats , 2016, Scientific Reports.