title: A form of synaptically induced metabotropic glutamate receptor-dependent long-term depression that does not require postsynaptic calcium.
abstract: The calcium control hypothesis posits that postsynaptic calcium increases are required to trigger synaptic plasticity, with large increases inducing LTP and small increases inducing LTD. In CA1 of the hippocampus, however, LTD induced by chemical activation of metabotropic glutamate receptors (agonist-LTD) is independent of increases in postsynaptic calcium. Here we tested whether LTD induced by pairing of presynaptic stimulation with postsynaptic depolarization (synaptic-LTD) is similarly calcium-independent. This protocol induced an NMDA-dependent LTP when paired at 0mV, which was converted to mGluR-dependent LTD when paired at -20mV. The LTD was not blocked by calcium chelation, blockers of L- or T-type voltage-dependent calcium channels, or hyperpolarization to -70mV. We conclude that synaptically induced mGluR-dependent LTD, like agonist induced mGluR LTD, does not require calcium influx for its induction.
authors.affiliation: Department of Neurology, Baylor College of Medicine, Houston, TX 77030, USA.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Kasten
authors.forename: Timothy
authors.initials: T
authors.lastname: Connelly
authors.forename: Yuan
authors.initials: Y
authors.lastname: Fan
authors.forename: Paul E
authors.initials: PE
authors.lastname: Schulz
mesh_terms: D000818:Animals; D056547:CA1 Region, Hippocampal / Q000166:cytology / Q000502:physiology*; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism*; D002614:Chelating Agents / Q000494:pharmacology; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials; D066298:In Vitro Techniques; D017774:Long-Term Potentiation / Q000187:drug effects; D036881:Long-Term Synaptic Depression / Q000187:drug effects; D018408:Patch-Clamp Techniques; D017966:Pyramidal Cells / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D018094:Receptors, Metabotropic Glutamate / Q000037:antagonists & inhibitors / Q000378:metabolism*; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism; D013569:Synapses / Q000502:physiology*; D055366:Synaptic Potentials
chemical_list: D015220:Calcium Channels; D002614:Chelating Agents; D018094:Receptors, Metabotropic Glutamate; D016194:Receptors, N-Methyl-D-Aspartate; D004533:Egtazic Acid; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D002118:Calcium