Group I metabotropic glutamate receptor (mGluR)-dependent long-term depression mediated via p38 mitogen-activated protein kinase is inhibited by previous high-frequency stimulation and activation of mGluRs and protein kinase C in the rat dentate gyrus in vitro.
The induction of synaptic plasticity is known to be influenced by the previous history of the synapse, a process termed metaplasticity. Here we demonstrate a novel metaplasticity in which group I metabotropic glutamate receptor (mGluR)-dependent long-term depression (LTD) of synaptic transmission is regulated by previous mGluR activation. In these studies, the group I mGluR-dependent LTD induced by the selective agonist (RS)-3,5-dihydroxyphenylglycine (DHPG-LTD) was inhibited by previous preconditioning brief high-frequency stimulation (HFS), regardless of whether the preconditioning HFS induced long-term potentiation. Blockade of NMDA receptors during the preconditioning HFS did not alter the inhibition of DHPG-LTD by the HFS. However, antagonism of mGluRs during the preconditioning HFS did prevent the inhibition of DHPG-LTD by the HFS. In addition, blocking PKC stimulation during the preconditioning HFS also prevented the inhibitory effect of HFS on DHPG-LTD. The DHPG-LTD itself was not inhibited by blocking PKC stimulation but was inhibited by blocking the p38 mitogen-activated protein kinase (MAPK) pathway. Thus, whereas the DHPG-LTD is mediated via activation of the p38 MAPK pathway, the inhibitory effects of preconditioning HFS on DHPG-LTD are mediated via stimulation of group I/II mGluRs, activation of PKC, and subsequent blocking of the functioning of group I mGluR.
Department of Physiology, Trinity College, Dublin 2, Ireland.
Anthony M
AM
Rush
Jianqun
J
Wu
Michael J
MJ
Rowan
Roger
R
Anwyl
D000818:Animals; D018891:Dentate Gyrus / Q000187:drug effects / Q000378:metabolism*; D004558:Electric Stimulation / Q000379:methods; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D066298:In Vitro Techniques; D017774:Long-Term Potentiation / Q000187:drug effects / Q000502:physiology; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology*; D009473:Neuronal Plasticity / Q000187:drug effects / Q000502:physiology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051381:Rats; D018094:Receptors, Metabotropic Glutamate / Q000819:agonists / Q000037:antagonists & inhibitors / Q000378:metabolism*; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology; D013995:Time; D048051:p38 Mitogen-Activated Protein Kinases
D004791:Enzyme Inhibitors; D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D018094:Receptors, Metabotropic Glutamate; D016194:Receptors, N-Methyl-D-Aspartate; D011493:Protein Kinase C; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases