Astrocyte Hypertrophy and Microglia Activation in the Rat Auditory Midbrain Is Induced by Electrical Intracochlear Stimulation

Neuron–glia interactions contribute to tissue homeostasis and functional plasticity in the mammalian brain, but it remains unclear how this is achieved. The potential of central auditory brain tissue for stimulation-dependent cellular remodeling was studied in hearing-experienced and neonatally deafened rats. At adulthood, both groups received an intracochlear electrode into the left cochlea and were continuously stimulated for 1 or 7 days after waking up from anesthesia. Normal hearing and deafness were assessed by auditory brainstem responses (ABRs). The effectiveness of stimulation was verified by electrically evoked ABRs as well as immunocytochemistry and in situ hybridization for the immediate early gene product Fos on sections through the auditory midbrain containing the inferior colliculus (IC). Whereas hearing-experienced animals showed a tonotopically restricted Fos response in the IC contralateral to electrical intracochlear stimulation, Fos-positive neurons were found almost throughout the contralateral IC in deaf animals. In deaf rats, the Fos response was accompanied by a massive increase of GFAP indicating astrocytic hypertrophy, and a local activation of microglial cells identified by IBA1. These glia responses led to a noticeable increase of neuron–glia approximations. Moreover, staining for the GABA synthetizing enzymes GAD65 and GAD67 rose significantly in neuronal cell bodies and presynaptic boutons in the contralateral IC of deaf rats. Activation of neurons and glial cells and tissue re-composition were in no case accompanied by cell death as would have been apparent by a Tunel reaction. These findings suggest that growth and activity of glial cells is crucial for the local adjustment of neuronal inhibition to neuronal excitation.

[1]  C. Matute,et al.  Glutamate‐mediated glial injury: Mechanisms and clinical importance , 2006, Glia.

[2]  P. Alves,et al.  Cultures of rat astrocytes challenged with a steady supply of glutamate: New model to study flux distribution in the glutamate–glutamine cycle , 2005, Glia.

[3]  J. Kelly,et al.  Contribution of AMPA and NMDA receptors to excitatory responses in the inferior colliculus , 2002, Hearing Research.

[4]  Zafer Soygüder.  Multiple neurotransmitter receptors contribute to the spinal Fos expression , 2005, Brain Research.

[5]  Ania K. Majewska,et al.  Microglial Interactions with Synapses Are Modulated by Visual Experience , 2010, PLoS biology.

[6]  R. Balice-Gordon,et al.  Astrocytes Regulate Inhibitory Synapse Formation via Trk-Mediated Modulation of Postsynaptic GABAA Receptors , 2005, The Journal of Neuroscience.

[7]  R. Illing,et al.  The Cochlear Implant in Action: Molecular Changes Induced in the Rat Central Auditory System , 2012 .

[8]  G. Pollak,et al.  Circuits That Innervate Excitatory-Inhibitory Cells in the Inferior Colliculus Obtained with In Vivo Whole Cell Recordings , 2013, The Journal of Neuroscience.

[9]  S. Oliet,et al.  Morphological plasticity of the rat supraoptic nucleus – cellular consequences , 2010, The European journal of neuroscience.

[10]  Edward L. Bartlett,et al.  A Monosynaptic GABAergic Input from the Inferior Colliculus to the Medial Geniculate Body in Rat , 1997, The Journal of Neuroscience.

[11]  Paul J. Lucassen,et al.  The Indispensable Roles of Microglia and Astrocytes during Brain Development , 2016, Front. Hum. Neurosci..

[12]  S. Beggs,et al.  P2X4-Receptor-Mediated Synthesis and Release of Brain-Derived Neurotrophic Factor in Microglia Is Dependent on Calcium and p38-Mitogen-Activated Protein Kinase Activation , 2009, The Journal of Neuroscience.

[13]  Mu-ming Poo,et al.  Activity-Dependent Matching of Excitatory and Inhibitory Inputs during Refinement of Visual Receptive Fields , 2005, Neuron.

[14]  M. Graeber,et al.  Microglia: biology and pathology , 2009, Acta Neuropathologica.

[15]  Grayson O. Sipe,et al.  Microglial P2Y12 is necessary for synaptic plasticity in mouse visual cortex , 2016, Nature Communications.

[16]  E. Keithley,et al.  The spatial representation of frequency in the rat dorsal cochlear nucleus and inferior colliculus , 1988, Hearing Research.

[17]  G. Knott,et al.  Plasticity of Astrocytic Coverage and Glutamate Transporter Expression in Adult Mouse Cortex , 2006, PLoS biology.

[18]  R. Illing,et al.  Neuronal subtype identity in the rat auditory brainstem as defined by molecular profile and axonal projection , 2009, Experimental Brain Research.

[19]  S. Nelson,et al.  Excitatory/Inhibitory Balance and Circuit Homeostasis in Autism Spectrum Disorders , 2015, Neuron.

[20]  C. Henneberger,et al.  Brain-derived neurotrophic factor modulates GABAergic synaptic transmission by enhancing presynaptic glutamic acid decarboxylase 65 levels, promoting asynchronous release and reducing the number of activated postsynaptic receptors , 2005, Neuroscience.

[21]  V. Perry,et al.  Microglial physiology: unique stimuli, specialized responses. , 2009, Annual review of immunology.

[22]  L. Leybaert,et al.  Release of gliotransmitters through astroglial connexin 43 hemichannels is necessary for fear memory consolidation in the basolateral amygdala , 2012, FASEB journal : official publication of the Federation of American Societies for Experimental Biology.

[23]  N. Kiang,et al.  Spontaneous spike discharges from single units in the cochlear nucleus after destruction of the cochlea. , 1966, Experimental neurology.

[24]  R. Illing,et al.  AP-1 activity rises by stimulation-dependent c-Fos expression in auditory neurons , 2008, Neuroreport.

[25]  F. Seil,et al.  Reduced cortical inhibitory synaptogenesis in organotypic cerebellar cultures developing in the absence of neuronal activity , 1994, The Journal of comparative neurology.

[26]  R. Illing,et al.  Nonlinear development of the populations of neurons expressing c-Fos under sustained electrical intracochlear stimulation in the rat auditory brainstem , 2010, Brain Research.

[27]  M. Nedergaard,et al.  Artifact versus reality—How astrocytes contribute to synaptic events , 2012, Glia.

[28]  Laurent Venance,et al.  Contribution of astrocytic glutamate and GABA uptake to corticostriatal information processing , 2011, The Journal of physiology.

[29]  N. Rooijen,et al.  Microglia Promote the Death of Developing Purkinje Cells , 2004, Neuron.

[30]  Nicole Rosskothen-Kuhl,et al.  The impact of hearing experience on signal integration in the auditory brainstem: A c-Fos study of the rat , 2012, Brain Research.

[31]  B. Khakh,et al.  P 2 X 4 receptors in activated C 8B 4 cells of cerebellar microglial origin , 2010 .

[32]  Dan H Sanes,et al.  The effect of bilateral deafness on excitatory and inhibitory synaptic strength in the inferior colliculus , 2002, The European journal of neuroscience.

[33]  D. Sanes,et al.  Deafness Disrupts Chloride Transporter Function and Inhibitory Synaptic Transmission , 2003, The Journal of Neuroscience.

[34]  N. Rosskothen-Kuhl,et al.  Counter-regulation of the AP-1 monomers pATF2 and Fos: Molecular readjustment of brainstem neurons in hearing and deaf adult rats after electrical intracochlear stimulation , 2016, Neuroscience.

[35]  I. Bechmann,et al.  CXCR3-Dependent Microglial Recruitment Is Essential for Dendrite Loss after Brain Lesion , 2004, The Journal of Neuroscience.

[36]  Michael E Greenberg,et al.  Communication between the synapse and the nucleus in neuronal development, plasticity, and disease. , 2008, Annual review of cell and developmental biology.

[37]  G. Ehret,et al.  Neuronal activity and tonotopy in the auditory system visualized by c-fos gene expression , 1991, Brain Research.

[38]  B. Khakh,et al.  P2X4 receptors in activated C8-B4 cells of cerebellar microglial origin , 2010, The Journal of general physiology.

[39]  R. Palmiter,et al.  Ablation of Neurons Expressing Agouti-Related Protein Activates Fos and Gliosis in Postsynaptic Target Regions , 2008, The Journal of Neuroscience.

[40]  Eric A Newman,et al.  Glial Cell Inhibition of Neurons by Release of ATP , 2003, The Journal of Neuroscience.

[41]  D. Miller,et al.  Quantitative neuronal c-Fos and c-Jun expression in Alzheimer’s disease1 1 To whom correspondence should be addressed. , 1998, Neurobiology of Aging.

[42]  R. Illing,et al.  Immediate early gene expression invoked by electrical intracochlear stimulation in some but not all types of neurons in the rat auditory brainstem , 2007, Experimental Neurology.

[43]  Richard J Smeyne,et al.  Continuous c-fos expression precedes programmed cell death in vivo , 1993, Nature.

[44]  W. Gan,et al.  ATP mediates rapid microglial response to local brain injury in vivo , 2005, Nature Neuroscience.

[45]  P. Tran Ba Huy,et al.  Influence of auditory deprivation upon the tonopic organization in the inferior colliculus: a Fos immunocytochemical study in the rat , 2003, The European journal of neuroscience.

[46]  S. Matsuura,et al.  Effects of kanamycin on the auditory evoked responses during postnatal development of the hearing of the rat. , 1979, Acta oto-laryngologica.

[47]  John H. Casseday,et al.  The Inferior Colliculus: A Hub for the Central Auditory System , 2002 .

[48]  O. Pascual,et al.  Astrocyte–Neuron Communication: Functional Consequences , 2012, Neurochemical Research.

[49]  R. Altschuler,et al.  Deafness-induced plasticity in the mature central auditory system , 1995, Neuroreport.

[50]  E. Lopez-Poveda,et al.  The inferior colliculus of the rat: Quantitative immunocytochemical study of GABA and glycine , 2005, Neuroscience.

[51]  S. Goldman,et al.  Astrocyte-mediated potentiation of inhibitory synaptic transmission , 1998, Nature Neuroscience.

[52]  L. Hughes,et al.  Detection of glutamate decarboxylase isoforms in rat inferior colliculus following acoustic exposure , 1999, Neuroscience.

[53]  S. Sherman,et al.  On the classification of pathways in the auditory midbrain, thalamus, and cortex , 2011, Hearing Research.

[54]  T. Tsumoto,et al.  Brain-derived neurotrophic factor increases inhibitory synapses, revealed in solitary neurons cultured from rat visual cortex , 2004, Neuroscience.

[55]  R. Illing,et al.  Transcription Factor Modulation and Expression in the Rat Auditory Brainstem Following Electrical Intracochlear Stimulation , 2002, Experimental Neurology.

[56]  H. Nakanishi,et al.  Potentiation of the NMDA receptor‐mediated responses through the activation of the glycine site by microglia secreting soluble factors , 2006, Glia.

[57]  S. Komune,et al.  Increase in glutamate-aspartate transporter (GLAST) mRNA during kanamycin-induced cochlear insult in rats , 1999, Hearing Research.

[58]  Shigeyuki Kuwada,et al.  GABAA Synapses Shape Neuronal Responses to Sound Intensity in the Inferior Colliculus , 2004, The Journal of Neuroscience.

[59]  Maiken Nedergaard,et al.  Astrocyte-mediated activation of neuronal kainate receptors. , 2004, Proceedings of the National Academy of Sciences of the United States of America.

[60]  R. Illing,et al.  Gap43 Transcription Modulation in the Adult Brain Depends on Sensory Activity and Synaptic Cooperation , 2014, PloS one.

[61]  Y. Shaham,et al.  New technologies for examining the role of neuronal ensembles in drug addiction and fear , 2013, Nature Reviews Neuroscience.

[62]  D. Bishop,et al.  Two Classes of GABAergic Neurons in the Inferior Colliculus , 2009, The Journal of Neuroscience.

[63]  R. Altschuler,et al.  Neonatal deafening causes changes in Fos protein induced by cochlear electrical stimulation , 2003, Journal of neurocytology.

[64]  P. Vidal,et al.  Modulation of inhibitory and excitatory synaptic transmission in rat inferior colliculus after unilateral cochleectomy: An in situ and immunofluorescence study , 2006, Neuroscience.

[65]  B. MacVicar,et al.  Activation of Neuronal NMDA Receptors Triggers Transient ATP-Mediated Microglial Process Outgrowth , 2014, The Journal of Neuroscience.

[66]  Baljit S. Khakh,et al.  Neuromodulation by Extracellular ATP and P2X Receptors in the CNS , 2012, Neuron.

[67]  A. Lalwani,et al.  The use of Preyer's reflex in evaluation of hearing in mice. , 2001, Acta oto-laryngologica.

[68]  Shigeyo Nagase,et al.  Changes in cochlear electrical stimulation induced Fos expression in the rat inferior colliculus following deafness , 2000, Hearing Research.

[69]  M. Nilsson,et al.  Dynamic structural remodelling of microglia in health and disease: A review of the models, the signals and the mechanisms , 2014, Brain, Behavior, and Immunity.

[70]  P. Vidal,et al.  Stimulation by cochlear implant in unilaterally deaf rats reverses the decrease of inhibitory transmission in the inferior colliculus , 2008, The European journal of neuroscience.

[71]  J. Yates,et al.  Microglia Promote Learning-Dependent Synapse Formation through Brain-Derived Neurotrophic Factor , 2013, Cell.