AMPA and metabotropic glutamate receptors cooperatively generate inspiratory‐like depolarization in mouse respiratory neurons in vitro

Excitatory transmission mediated by AMPA receptors is critical for respiratory rhythm generation. However, the role of AMPA receptors has not been fully explored. Here we tested the functional role of AMPA receptors in inspiratory neurons of the neonatal mouse preBötzinger complex (preBötC) using an in vitro slice model that retains active respiratory function. Immediately before and during inspiration, preBötC neurons displayed envelopes of depolarization, dubbed inspiratory drive potentials, that required AMPA receptors but largely depended on the Ca2+‐activated non‐specific cation current (ICAN). We showed that AMPA receptor‐mediated depolarization opened voltage‐gated Ca2+ channels to directly evoke ICAN. Inositol 1,4,5‐trisphosphate receptor‐mediated intracellular Ca2+ release also evoked ICAN. Inositol 1,4,5‐trisphosphate receptors acted downstream of group I metabotropic glutamate receptor activity but, here too, AMPA receptor‐mediated Ca2+ influx was essential to trigger the metabotropic glutamate receptor contribution to inspiratory drive potential generation. This study helps to elucidate the role of excitatory transmission in respiratory rhythm generation in vitro. AMPA receptors in preBötC neurons initiate convergent signaling pathways that evoke post‐synaptic ICAN, which underlies inspiratory drive potentials. The coupling of AMPA receptors with ICAN suggests that latent burst‐generating intrinsic conductances are recruited by excitatory synaptic interactions among preBötC neurons in the context of respiratory network activity in vitro, exemplifying a rhythmogenic mechanism based on emergent properties of the network.

[1]  J. Foskett,et al.  Graded recruitment and inactivation of single InsP3 receptor Ca2+‐release channels: implications for quartal Ca2+release , 2006, The Journal of physiology.

[2]  J. C. Smith,et al.  Functional respiratory rhythm generating networks in neonatal mice lacking NMDAR1 gene. , 1997, Journal of neurophysiology.

[3]  I. Homma,et al.  Contribution of Ca2+‐dependent conductances to membrane potential fluctuations of medullary respiratory neurons of newborn rats in vitro , 2003, The Journal of physiology.

[4]  J. Feldman,et al.  NMDA receptors in preBötzinger complex neurons can drive respiratory rhythm independent of AMPA receptors , 2007, The Journal of physiology.

[5]  J. Feldman,et al.  Looking for inspiration: new perspectives on respiratory rhythm , 2006, Nature Reviews Neuroscience.

[6]  J C Smith,et al.  Intrinsic bursters increase the robustness of rhythm generation in an excitatory network. , 2007, Journal of neurophysiology.

[7]  R. Vennekens,et al.  Comparison of functional properties of the Ca2+-activated cation channels TRPM4 and TRPM5 from mice. , 2005, Cell calcium.

[8]  M. Hollmann,et al.  Expression of 15 Glutamate Receptor Subunits and Various Splice Variants in Tissue Slices and Single Neurons of Brainstem Nuclei and Potential Functional Implications , 2000, Journal of neurochemistry.

[9]  C. Heckman,et al.  Paradoxical effect of QX-314 on persistent inward currents and bistable behavior in spinal motoneurons in vivo. , 1999, Journal of neurophysiology.

[10]  M. Iino,et al.  Cross Talk between Metabotropic and Ionotropic Glutamate Receptor-Mediated Signaling in Parallel Fiber-Induced Inositol 1,4,5-Trisphosphate Production in Cerebellar Purkinje Cells , 2004, The Journal of Neuroscience.

[11]  Marinov Bs,et al.  Dose-dependent potentiation and inhibition of single Ca2+-activated K+ channels by flufenamic acid. , 2000 .

[12]  Jean-François Vibert,et al.  Respiratory-like rhythmic activity can be produced by an excitatory network of non-pacemaker neuron models. , 2004, Journal of neurophysiology.

[13]  James Watras,et al.  Bell-shaped calcium-response curves of lns(l,4,5)P3- and calcium-gated channels from endoplasmic reticulum of cerebellum , 1991, Nature.

[14]  Jeffrey C. Smith,et al.  Persistent Na+ and K+-Dominated Leak Currents Contribute to Respiratory Rhythm Generation in the Pre-Bötzinger Complex In Vitro , 2008, The Journal of Neuroscience.

[15]  C. D. Del Negro,et al.  Neurokinin receptor-expressing pre-botzinger complex neurons in neonatal mice studied in vitro. , 2007, Journal of neurophysiology.

[16]  D. Speck,et al.  Differential effects of excitatory amino acid receptor antagonism in the ventral respiratory group , 1999, Brain Research.

[17]  A. El Manira,et al.  Signaling Mechanisms of Metabotropic Glutamate Receptor 5 Subtype and Its Endogenous Role in a Locomotor Network , 2002, The Journal of Neuroscience.

[18]  J. Feldman,et al.  AMPA receptor activation and phosphatase inhibition affect neonatal rat respiratory rhythm generation , 1998, The Journal of physiology.

[19]  J. Lacaille,et al.  Differential Regulation of Metabotropic Glutamate Receptor- and AMPA Receptor-Mediated Dendritic Ca2+ Signals by Presynaptic and Postsynaptic Activity in Hippocampal Interneurons , 2005, The Journal of Neuroscience.

[20]  J. Feldman,et al.  Modulation of neural network activity in vitro by cyclothiazide, a drug that blocks desensitization of AMPA receptors , 1995, The Journal of neuroscience : the official journal of the Society for Neuroscience.

[21]  Jeffrey C. Smith,et al.  Neuronal pacemaker for breathing visualized in vitro , 1999, Nature.

[22]  S. Grillner,et al.  Intracellular QX-314 causes depression of membrane potential oscillations in lamprey spinal neurons during fictive locomotion. , 2002, Journal of neurophysiology.

[23]  Jan-Marino Ramirez,et al.  Differential Contribution of Pacemaker Properties to the Generation of Respiratory Rhythms during Normoxia and Hypoxia , 2004, Neuron.

[24]  D. Richter,et al.  Calcium-dependent conductances control neurones involved in termination of inspiration in cats , 1995, Neuroscience Letters.

[25]  P. Delmas,et al.  Signaling Microdomains Define the Specificity of Receptor-Mediated InsP3 Pathways in Neurons , 2002, Neuron.

[26]  J. Champagnat,et al.  Electroresponsive properties and membrane potential trajectories of three types of inspiratory neurons in the newborn mouse brain stem in vitro. , 1996, Journal of neurophysiology.

[27]  I. Greenwood,et al.  Comparison of the effects of fenamates on Ca‐activated chloride and potassium currents in rabbit portal vein smooth muscle cells , 1995, British journal of pharmacology.

[28]  Consuelo Morgado-Valle,et al.  Respiratory Rhythm An Emergent Network Property? , 2002, Neuron.

[29]  J. Feldman,et al.  Modulation of AMPA receptors by cAMP‐dependent protein kinase in PreBötzinger complex inspiratory neurons regulates respiratory rhythm in the rat , 2003, The Journal of physiology.

[30]  K. Jellinger.  Understanding G protein‐coupled receptors and their role in the CNS (Molecular and Cellular Neurobiology) , 2003 .

[31]  D. Richter,et al.  Calcium currents and calcium‐dependent potassium currents in mammalian medullary respiratory neurones. , 1993, The Journal of physiology.

[32]  J. Feldman,et al.  Electrical Coupling and Excitatory Synaptic Transmission between Rhythmogenic Respiratory Neurons in the PreBötzinger Complex , 2000, The Journal of Neuroscience.

[33]  Alla Borisyuk,et al.  The Dynamic Range of Bursting in a Model Respiratory Pacemaker Network , 2005, SIAM J. Appl. Dyn. Syst..

[34]  S L Mironov,et al.  Metabotropic glutamate receptors activate dendritic calcium waves and TRPM channels which drive rhythmic respiratory patterns in mice , 2008, The Journal of physiology.

[35]  George J. Augustine,et al.  Local calcium signalling by inositol-1,4,5-trisphosphate in Purkinje cell dendrites , 1998, Nature.

[36]  M. Berridge,et al.  The organisation and functions of local Ca(2+) signals. , 2001, Journal of cell science.

[37]  W. N. Ross,et al.  Synergistic Release of Ca2+ from IP3-Sensitive Stores Evoked by Synaptic Activation of mGluRs Paired with Backpropagating Action Potentials , 1999, Neuron.

[38]  G. Funk,et al.  High Sensitivity to Neuromodulator-Activated Signaling Pathways at Physiological [K+] of Confocally Imaged Respiratory Center Neurons in On-Line-Calibrated Newborn Rat Brainstem Slices , 2006, The Journal of Neuroscience.

[39]  J. Champagnat,et al.  Thyrotropin-releasing hormone (TRH) depolarizes a subset of inspiratory neurons in the newborn mouse brain stem in vitro. , 1996, Journal of neurophysiology.

[40]  J. Feldman,et al.  Inspiratory bursts in the preBötzinger complex depend on a calcium‐activated non‐specific cation current linked to glutamate receptors in neonatal mice , 2007, Journal of Physiology.

[41]  G. Hu.  Effects of depolarization and QX-314 injection on slow prepotentials in rat hippocampal pyramidal neurones in vitro. , 1991, Acta physiologica Scandinavica.

[42]  J. C. Smith,et al.  Role of excitatory amino acids in the generation and transmission of respiratory drive in neonatal rat. , 1991, The Journal of physiology.

[43]  J. Feldman,et al.  Sodium and Calcium Current-Mediated Pacemaker Neurons and Respiratory Rhythm Generation , 2005, The Journal of Neuroscience.

[44]  G. Prestwich,et al.  Phosphatidylinositol 4,5‐bisphosphate regulates inspiratory burst activity in the neonatal mouse preBötzinger complex , 2007, The Journal of physiology.

[45]  Marino DiFranco,et al.  Somatic Ca2+ transients do not contribute to inspiratory drive in preBötzinger Complex neurons , 2008, The Journal of physiology.

[46]  K. Ballanyi,et al.  Synaptic inhibition in the isolated respiratory network of neonatal rats , 1998, The European journal of neuroscience.

[47]  A. Manira,et al.  Neuromodulation via Conditional Release of Endocannabinoids in the Spinal Locomotor Network , 2005, Neuron.

[48]  Youngnam Kang,et al.  Involvement of persistent Na+ current in spike initiation in primary sensory neurons of the rat mesencephalic trigeminal nucleus. , 2007, Journal of neurophysiology.

[49]  D. Richter,et al.  The effects of QX-314 on medullary respiratory neurones , 1987, Brain Research.

[50]  D. Richter,et al.  Calcium currents in respiratory neurons of the cat in vivo , 1999, Pflügers Archiv.

[51]  J. Feldman,et al.  PreBötzinger complex and pacemaker neurons: hypothesized site and kernel for respiratory rhythm generation. , 1998, Annual review of physiology.

[52]  I. Bezprozvanny,et al.  Functional characterization of mammalian inositol 1,4,5-trisphosphate receptor isoforms. , 2005, Biophysical journal.

[53]  J. Teulon.  Ca2+-Activated Non-Selective Cation Channels , 2000 .

[54]  B. Marinov,et al.  Dose-dependent potentiation and inhibition of single Ca2+-activated K+ channels by flufenamic acid. , 2000, Membrane & cell biology.

[55]  Donald R McCrimmon,et al.  Sodium Currents in Medullary Neurons Isolated from the Pre-Bötzinger Complex Region , 2005, The Journal of Neuroscience.

[56]  J. Feldman,et al.  Role of persistent sodium current in mouse preBötzinger Complex neurons and respiratory rhythm generation , 2007, The Journal of physiology.

[57]  J C Smith,et al.  Generation and transmission of respiratory oscillations in medullary slices: role of excitatory amino acids. , 1993, Journal of neurophysiology.

[58]  I. Solomon.  Ionotropic excitatory amino acid receptors in pre-Botzinger complex play a modulatory role in hypoxia-induced gasping in vivo. , 2004, Journal of applied physiology.

[59]  S. M. Goldin,et al.  Calcium as a coagonist of inositol 1,4,5-trisphosphate-induced calcium release. , 1991, Science.

[60]  G. Funk,et al.  Distinct receptors underlie glutamatergic signalling in inspiratory rhythm‐generating networks and motor output pathways in neonatal rat , 2008, The Journal of physiology.

[61]  J. Ramirez,et al.  Pattern-specific synaptic mechanisms in a multifunctional network. I. Effects of alterations in synapse strength. , 2006, Journal of neurophysiology.