title: Metabotropic glutamate receptors in the rat nucleus accumbens.
abstract: The effects of glutamate metabotropic receptors (mGluRs) on excitatory transmission in the nucleus accumbens were investigated using electrophysiological techniques in rat nucleus accumbens slices. The broad-spectrum mGluR agonist (1S,3R)-1-aminocyclopentyl-1,3-dicarboxylate, the mGluR group 2 selective agonists (S)-4-carboxy-3-hydroxyphenylglycine, (1S,3S)-ACPD) and (2S,1'S,2'S)-2-(2'-carboxycyclopropyl)glycine (L-CCG1), and the mGluR group 3 specific agonist L-2-amino-4-phosphonobutyrate (L-AP4) all reversibly inhibited evoked excitatory synaptic responses. The specific group 1 mGluR agonist (R,S)-3,5-dihydroxyphenylglycine [(R,S)-DHPG] did not depress transmission. Dose-response curves showed that the rank order of agonist potencies was: L-CCG1 > L-AP4 > (1S,3S)-ACPD. Group 2 and 3 mGluRs inhibited transmission via a presynaptic mechanism, as they increased paired-pulse facilitation, decreased the frequency of miniature excitatory postsynaptic currents and had no effect on their amplitude. The mGluRs did not inhibit transmitter release by reducing voltage-dependent Ca2+ currents through N- or P-type Ca2+ channels, as inhibition persisted in the presence of omega-conotoxin-GVIA or omega-Aga-IVA. The depression induced by mGluRs was not affected by specific antagonists of dopamine D1, GABA-B or adenosine A1 receptors, indicating direct effects. Finally, (R,S)-DHPG specifically blocked the postsynaptic afterhyperpolarization current (I(AHP)). Our results represent the first direct demonstration of functional mGluRs in the nucleus accumbens of the rat.
authors.affiliation: CNRS UPR 9023, Montpellier, France.
authors.forename: O
authors.initials: O
authors.lastname: Manzoni
authors.forename: J M
authors.initials: JM
authors.lastname: Michel
authors.forename: J
authors.initials: J
authors.lastname: Bockaert
mesh_terms: D000241:Adenosine / Q000378:metabolism; D000818:Animals; D015220:Calcium Channels / Q000502:physiology; D000242:Cyclic AMP / Q000378:metabolism; D004298:Dopamine / Q000502:physiology; D066298:In Vitro Techniques; D008297:Male; D009433:Neural Inhibition; D009714:Nucleus Accumbens / Q000378:metabolism*; D017729:Presynaptic Terminals / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D018080:Receptors, GABA-B / Q000502:physiology; D018094:Receptors, Metabotropic Glutamate / Q000819:agonists / Q000037:antagonists & inhibitors / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects
chemical_list: D015220:Calcium Channels; D018080:Receptors, GABA-B; D018094:Receptors, Metabotropic Glutamate; D000242:Cyclic AMP; D000241:Adenosine; D004298:Dopamine