Metabotropic glutamate receptors mediate expression of LTP in slices of rat visual cortex.
Long-term-potentiation (LTP) can be induced by application of a standard theta-burst stimulation protocol in slice preparations of the neocortex. This type of LTP is known to be dependent on the activation of NMDA receptors. The present study used specific experimental conditions to evoke a non-NMDA receptor mediated type of LTP. By use of weak theta-burst stimulation (wTBS) we describe a non-NMDA receptor dependent LTP in rat visual cortex in vitro, which is sensitive to an antagonist of metabotropic glutamate receptors (mGluR). In slices of the visual cortex we stimulated ascending inputs in cortical layer IV and recorded extracellular field potentials (FPs) from cortical layers II/III. In disinhibited slices (with 1 microm picrotoxin), a wTBS induced LTP to 138% of control. The expression of this potentiation was insensitive to the NMDA-receptor antagonist, D-AP5, but could be abolished by application of the mGluR antagonist MCPG. These data suggest an NMDA-independent mechanism for LTP induction in the visual cortex which can be observed in layer II/III neurons.
Huemmeke
Markus
M
Department of Neurophysiology, Ruhr-University Bochum, Germany.
Eysel
Ulf T
UT
Mittmann
Thomas
T
D000200:Action Potentials; D000818:Animals; D001565:Benzoates / Q000494:pharmacology; D004338:Drug Combinations; D004558:Electric Stimulation / Q000379:methods; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005110:Extracellular Space / Q000502:physiology; D005998:Glycine / Q000031:analogs & derivatives* / Q000494:pharmacology; D066298:In Vitro Techniques; D017774:Long-Term Potentiation / Q000187:drug effects / Q000502:physiology*; D010852:Picrotoxin / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D018094:Receptors, Metabotropic Glutamate / Q000502:physiology*; D013826:Theta Rhythm; D015534:Trans-Activators / Q000494:pharmacology; D014793:Visual Cortex / Q000502:physiology*; D014795:Visual Pathways / Q000502:physiology
D001565:Benzoates; D004338:Drug Combinations; D018691:Excitatory Amino Acid Antagonists; D005998:Glycine; D010852:Picrotoxin; D018094:Receptors, Metabotropic Glutamate; D015534:Trans-Activators; C095901:transcription factor AP-5; C079694:alpha-methyl-4-carboxyphenylglycine