title: P2Y1 receptor-mediated potentiation of inspiratory motor output in neonatal rat in vitro.
abstract: PreBötzinger complex inspiratory rhythm-generating networks are excited by metabotropic purinergic receptor subtype 1 (P2Y1R) activation. Despite this, and the fact that inspiratory MNs express P2Y1Rs, the role of P2Y1Rs in modulating motor output is not known for any MN pool. We used rhythmically active brainstem-spinal cord and medullary slice preparations from neonatal rats to investigate the effects of P2Y1R signalling on inspiratory output of phrenic and XII MNs that innervate diaphragm and airway muscles, respectively. MRS2365 (P2Y1R agonist, 0.1 mm) potentiated XII inspiratory burst amplitude by 60 ± 9%; 10-fold higher concentrations potentiated C4 burst amplitude by 25 ± 7%. In whole-cell voltage-clamped XII MNs, MRS2365 evoked small inward currents and potentiated spontaneous EPSCs and inspiratory synaptic currents, but these effects were absent in TTX at resting membrane potential. Voltage ramps revealed a persistent inward current (PIC) that was attenuated by: flufenamic acid (FFA), a blocker of the Ca(2+)-dependent non-selective cation current ICAN; high intracellular concentrations of BAPTA, which buffers Ca(2+) increases necessary for activation of ICAN; and 9-phenanthrol, a selective blocker of TRPM4 channels (candidate for ICAN). Real-time PCR analysis of mRNA extracted from XII punches and laser-microdissected XII MNs revealed the transcript for TRPM4. MRS2365 potentiated the PIC and this potentiation was blocked by FFA, which also blocked the MRS2365 potentiation of glutamate currents. These data suggest that XII MNs are more sensitive to P2Y1R modulation than phrenic MNs and that the P2Y1R potentiation of inspiratory output occurs in part via potentiation of TRPM4-mediated ICAN, which amplifies inspiratory inputs.
authors.affiliation: Department of Physiology, Centre for Neuroscience, Women and Children's Health Research Institute (WCHRI), Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: T S
authors.initials: TS
authors.lastname: Alvares
authors.affiliation: Department of Physiology, Centre for Neuroscience, Women and Children's Health Research Institute (WCHRI), Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: A L
authors.initials: AL
authors.lastname: Revill
authors.affiliation: Department of Physiology, Centre for Neuroscience, Women and Children's Health Research Institute (WCHRI), Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: A G
authors.initials: AG
authors.lastname: Huxtable
authors.affiliation: Department of Physiology, Centre for Neuroscience, Women and Children's Health Research Institute (WCHRI), Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: C D
authors.initials: CD
authors.lastname: Lorenz
authors.affiliation: Department of Physiology, Centre for Neuroscience, Women and Children's Health Research Institute (WCHRI), Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada gf@ualberta.ca.
authors.forename: G D
authors.initials: GD
authors.lastname: Funk
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001933:Brain Stem / Q000502:physiology; D007002:Hypoglossal Nerve / Q000502:physiology*; D066298:In Vitro Techniques; D001239:Inhalation / Q000502:physiology; D009046:Motor Neurons / Q000502:physiology*; D010791:Phrenic Nerve / Q000502:physiology*; D017207:Rats, Sprague-Dawley; D017208:Rats, Wistar; D058472:Receptors, Purinergic P2Y1 / Q000502:physiology*; D013116:Spinal Cord / Q000502:physiology
chemical_list: D058472:Receptors, Purinergic P2Y1