title: Presynaptic modulation by group III metabotropic glutamate receptors (mGluRs) of the excitatory postsynaptic potential mediated by mGluR1 in rat cerebellar Purkinje cells.
abstract: Purkinje neurons were recorded from rat cerebellar slices. Parallel fibres stimulation elicited a fast excitatory postsynaptic potential (EPSP) mediated by ionotropic glutamate (iGluR) -amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors followed by the inhibitory gamma-aminobutyric acidA (GABAA)-dependent postsynaptic potential. In the presence of antagonists for iGluRs and for GABAA receptors, brief tetanic activation evoked a slow metabotropic glutamate receptor (mGluR)-dependent EPSP (mGluR-EPSP). This mGluR-EPSP was blocked by the selective mGluR1 antagonists LY367385 and CPCCOEt, but not by the mGluR5 antagonist MPEP. Group II agonists affected neither iGluR-EPSP nor mGluR-EPSP. Conversely, L-AP4 and L-SOP, group III mGluR agonists, inhibited both iGluR- and mGluR-EPSPs. The depolarisations evoked by both AMPA and group I agonists were unaffected, indicating a presynaptic action of group III mGluRs. These data suggest that glutamate released by parallel fibres activates group III mGluR autoreceptors, depressing both iGluR- and mGluR1-mediated EPSPs.
authors.affiliation: Fondazione Santa Lucia-IRCCS, Rome, Italy.
authors.forename: M C
authors.initials: MC
authors.lastname: Miniaci
authors.forename: P
authors.initials: P
authors.lastname: Bonsi
authors.forename: F
authors.initials: F
authors.lastname: Tempia
authors.forename: P
authors.initials: P
authors.lastname: Strata
authors.forename: A
authors.initials: A
authors.lastname: Pisani
mesh_terms: D000818:Animals; D001565:Benzoates; D001640:Bicuculline / Q000494:pharmacology; D002531:Cerebellum / Q000502:physiology*; D004558:Electric Stimulation; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology*; D018756:GABA Antagonists / Q000494:pharmacology; D005998:Glycine / Q000031:analogs & derivatives / Q000494:pharmacology; D008297:Male; D011689:Purkinje Cells / Q000378:metabolism*; D011810:Quinoxalines / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D018094:Receptors, Metabotropic Glutamate / Q000502:physiology*; D017661:Receptors, Presynaptic / Q000502:physiology*
chemical_list: D001565:Benzoates; D018691:Excitatory Amino Acid Antagonists; D018756:GABA Antagonists; D011810:Quinoxalines; D018094:Receptors, Metabotropic Glutamate; D017661:Receptors, Presynaptic; C104077:metabotropic glutamate receptor type 1; C062865:2,3-dioxo-6-nitro-7-sulfamoylbenzo(f)quinoxaline; C079694:alpha-methyl-4-carboxyphenylglycine; D005998:Glycine; D001640:Bicuculline