title: Activation of metabotropic glutamate receptors induces an inward current in rat dopamine mesencephalic neurons.
abstract: To investigate the electrophysiological effects of the stimulation of the metabotropic excitatory amino acid receptors, we applied trans-1-amino-cyclopentane-1,3-dicarboxylate, an agonist of this type of receptors, on presumed rat dopamine cells intracellularly recorded in vitro. Trans-1-amino-cyclopentane-1,3-dicarboxylate (3-30 microM, t-ACPD) caused a sustained increase of the spontaneous firing rate and a depolarization. When the membrane potential was held at about the resting level (-50, -60 mV), by the single-electrode voltage-clamp technique, t-ACPD induced an inward current. In 57% of the tested cells the inward current was associated with a decrease of the apparent input conductance. In the remaining cells no obvious changes in membrane conductance were observed. The active form of t-ACPD, (1S,3R)-1-amino-cyclopentane-1,3-dicarboxylate [3-50 microM, (1S,3R)-ACPD] also produced a reversible inward current on the dopaminergic cells and this was antagonized by (S)-4-carboxy-3-hydroxyphenylglycine (300 microM), a selective antagonist of the (1S,3R)-ACPD-induced depolarization on central neurons. The (1S,3R)-ACPD-induced inward current was not antagonized by L-2-amino-3-phosphonopropionic acid (100 microM), an antagonist of the t-ACPD-induced activation of inositide synthesis. 6-cyano-7-nitroquinoxaline-2,3-dione (10 microM), an alfa-amino-3-hydroxy-5- methyl-isoxazole propionic acid/kainate antagonist, DL-amino-5-phosphonopentanoic acid (30 microM), an N-methyl-D-aspartate antagonist, and scopolamine (10 microM), a muscarinic antagonist, did not significantly affect the actions of t-ACPD. A block of synaptic transmission obtained by applying tetrodotoxin failed to prevent the action of t-ACPD.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Dip. Sanità Pubblica, Università di Roma Tor Vergata, Italy.
authors.forename: N B
authors.initials: NB
authors.lastname: Mercuri
authors.forename: F
authors.initials: F
authors.lastname: Stratta
authors.forename: P
authors.initials: P
authors.lastname: Calabresi
authors.forename: A
authors.initials: A
authors.lastname: Bonci
authors.forename: G
authors.initials: G
authors.lastname: Bernardi
mesh_terms: D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D000200:Action Potentials / Q000187:drug effects; D000409:Alanine / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D003515:Cycloleucine / Q000031:analogs & derivatives* / Q000494:pharmacology; D004298:Dopamine / Q000378:metabolism*; D004594:Electrophysiology; D005260:Female; D005998:Glycine / Q000031:analogs & derivatives / Q000494:pharmacology; D008297:Male; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D011188:Potassium / Q000494:pharmacology; D011810:Quinoxalines / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D018094:Receptors, Metabotropic Glutamate / Q000187:drug effects* / Q000502:physiology; D013268:Stimulation, Chemical; D013779:Tetrodotoxin / Q000494:pharmacology; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / Q000494:pharmacology
chemical_list: D011810:Quinoxalines; D018094:Receptors, Metabotropic Glutamate; C000211:2-amino-3-phosphonopropionic acid; D003515:Cycloleucine; C036361:1-amino-1,3-dicarboxycyclopentane; C078245:4-carboxy-3-hydroxyphenylglycine; D013779:Tetrodotoxin; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; D000409:Alanine; D011188:Potassium; D005998:Glycine; D004298:Dopamine