title: Agonist action of (RS)-alpha-methyl-4-carboxyphenylglycine (MCPG) in the amygdala.
abstract: Glutamatergic excitatory postsynaptic potentials (EPSPs) in the basolateral amygdala (BLA) are reduced in amplitude following agonist activation of presynaptic metabotropic glutamate receptors (mGluR). In this study, the effect of a presumed mGluR antagonist, (RS)-alpha-methyl-4-carboxyphenylglycine (MCPG), was investigated on the EPSP recorded intracellularly in BLA neurons. Superfusion of MCPG (500 microM) significantly reduced the amplitude of evoked EPSPs. In the presence of MCPG, postsynaptic responses to alpha-amino-3-hydroxy-5-methyl-4-isoxazoleproprionic acid (AMPA, 1 microM) were unaltered while responses to N-methyl-D-aspartate (NMDA, 3-5 microM) were potentiated. These data suggest that the MCPG-induced reduction of EPSP amplitude is due to a mGluR agonist action at a presynaptic mGluR 'autoreceptor'.
authors.affiliation: Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston 77555-1031, USA.
authors.forename: N B
authors.initials: NB
authors.lastname: Keele
authors.forename: V
authors.initials: V
authors.lastname: Arvanov
authors.forename: K
authors.initials: K
authors.lastname: Holmes
authors.forename: P
authors.initials: P
authors.lastname: Shinnick-Gallagher
mesh_terms: D000679:Amygdala / Q000187:drug effects*; D000818:Animals; D001565:Benzoates / Q000494:pharmacology*; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology*; D005998:Glycine / Q000031:analogs & derivatives* / Q000494:pharmacology; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D018091:Receptors, AMPA / Q000187:drug effects; D018094:Receptors, Metabotropic Glutamate / Q000819:agonists*; D017661:Receptors, Presynaptic / Q000187:drug effects; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology; D013779:Tetrodotoxin / Q000494:pharmacology
chemical_list: D001565:Benzoates; D018691:Excitatory Amino Acid Antagonists; D018091:Receptors, AMPA; D018094:Receptors, Metabotropic Glutamate; D017661:Receptors, Presynaptic; C079694:alpha-methyl-4-carboxyphenylglycine; D013779:Tetrodotoxin; D005998:Glycine