title: Regulation of intrinsic and synaptic properties of neonatal rat trigeminal motoneurons by metabotropic glutamate receptors.
abstract: We studied how metabotropic glutamate receptor (mGluR) activation modifies the synaptic and intrinsic membrane properties of neonatal rat trigeminal motoneurons using the broad-spectrum mGluR agonist (1S,3R)-1-amino-1,3-cyclopentane-dicarboxylic acid [(1S,3R)-ACPD], group I/II antagonist (+/-)-alpha-methyl-4-carboxy-phenylglycine (MCPG), and group III agonist L-2-amino-4-phosphonobutanoate (L-AP4). (1S,3R)-ACPD depressed excitatory transmission to trigeminal motoneurons presynaptically and postsynaptically via presynaptic inhibition and by reducing the currents carried by ionotropic glutamate receptors selective for AMPA. (1S,3R)-ACPD also depolarized trigeminal motoneurons and increased input resistance by suppressing a Ba2+-sensitive leakage K+ current. These effects were not mimicked by L-AP4 (100-200 microM). High-threshold Ca2+ currents were also suppressed by (1S,3R)-ACPD. Repetitive stimulation of excitatory premotoneurons mimicked the postsynaptic effects of (1S, 3R)-ACPD. The postsynaptic effects of (1S,3R)-ACPD and repetitive stimulation were both antagonized by MCPG, suggesting that mGluRs were similarly activated in both experiments. We conclude that mGluRs can be recruited endogenously by glutamatergic premotoneurons and that mGluR-mediated depression of excitatory transmission, combined with increased postsynaptic excitability, enhances the signal-to-noise ratio of oral-related synaptic input to trigeminal motoneurons during rhythmical jaw movements.
authors.affiliation: Department of Physiological Science, University of California at Los Angeles, Los Angeles, California 90095-1586, USA.
authors.forename: C A
authors.initials: CA
authors.lastname: Del Negro
authors.forename: S H
authors.initials: SH
authors.lastname: Chandler
mesh_terms: D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D001565:Benzoates / Q000494:pharmacology; D003515:Cycloleucine / Q000031:analogs & derivatives / Q000494:pharmacology; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005998:Glycine / Q000031:analogs & derivatives / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009046:Motor Neurons / Q000737:chemistry / Q000502:physiology*; D016202:N-Methylaspartate / Q000494:pharmacology; D018696:Neuroprotective Agents / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D051381:Rats; D018094:Receptors, Metabotropic Glutamate / Q000502:physiology*; D009435:Synaptic Transmission / Q000502:physiology*; D013779:Tetrodotoxin / Q000494:pharmacology; D014278:Trigeminal Nuclei / Q000737:chemistry / Q000166:cytology*; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / Q000494:pharmacology
chemical_list: D001565:Benzoates; D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D018696:Neuroprotective Agents; D018094:Receptors, Metabotropic Glutamate; D003515:Cycloleucine; C036361:1-amino-1,3-dicarboxycyclopentane; C079694:alpha-methyl-4-carboxyphenylglycine; D013779:Tetrodotoxin; D016202:N-Methylaspartate; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; D005998:Glycine