Activation of mGluRII induces LTD via activation of protein kinase A and protein kinase C in the dentate gyrus of the hippocampus in vitro.
The involvement of metabotropic glutamate receptor group II (mGluRII) in the induction of long-term depression (LTD) was investigated in the medial perforant path of the rat dentate gyrus, a region with a very high density of mGluRII. Perfusion of either of two potent mGluRII agonists, (2S,1R,2R,3R)-2-(2S, 1'R, 2'R, 3'R)-2 (2' 3'-dicarboxycyclopropyl)glycine (DCG-IV) or (+)-2- aminobicyclo[3.1.0]hexane-2-6-dicarboxylic acid (LY354740) induced a reversible inhibition of the field EPSP followed, upon washout of the agonist, by LTD. The reversible inhibition was associated with a change in paired pulse depression, indicating an underlying presynaptic reduction in the probability of transmitter release, whereas the LTD was not associated with a change in paired pulse depression, indicating either a presynaptic reduction in the number of active release sites, or a postsynaptic change. Further evidence that the DCG-IV-induced LTD was generated by activation of mGluRII was the finding that the mGluRII antagonist (RS)-alpha-methylserine-O-phosphate monophenylphosphoryl ester (MSOPPE) prevented the induction of the LTD induced by DCG-IV. The DCG-IV-induced LTD showed mutual occlusion with LFS-induced LTD. The generation of the agonist-induced LTD required, in part, activation of N-methyl-D-aspartate receptors (NMDAR), as LTD induction was partially blocked in the presence of the NMDAR antagonist D-2-amino-5-phosphonopentanoate (AP5). Evidence for involvement of protein kinase C (PKC) and protein kinase (PKA) in the induction of LTD by activation of mGluRII was obtained by showing an inhibition of the DCG-IV-induced LTD by the PKC inhibitors Ro-31-8220 and bisindolylmaleimide I, and also by the PKA inhibitor H-89. The study demonstrates that activation of mGluRII induces LTD via activation the PKA and PKC pathways in the medial perforant path of the dentate gyrus.
Huang
L
L
Department of Physiology, Pharmacology and Therapeutics, Trinity College, Dublin, Ireland.
Killbride
J
J
Rowan
M J
MJ
Anwyl
R
R
D000818:Animals; D017868:Cyclic AMP-Dependent Protein Kinases / Q000187:drug effects*; D018891:Dentate Gyrus / Q000187:drug effects* / Q000201:enzymology; D004789:Enzyme Activation; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects; D066298:In Vitro Techniques; D009473:Neuronal Plasticity / Q000187:drug effects*; D017729:Presynaptic Terminals / Q000187:drug effects; D011493:Protein Kinase C / Q000187:drug effects*; D051381:Rats; D018094:Receptors, Metabotropic Glutamate / Q000819:agonists*; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects
D018094:Receptors, Metabotropic Glutamate; D016194:Receptors, N-Methyl-D-Aspartate; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C