title: Evidence for altered NMDA receptor function as a basis for metaplasticity in visual cortex.
abstract: Sensory deprivation alters the properties of synaptic plasticity induced in the superficial layers of the visual cortex, facilitating long-term potentiation and reducing long-term depression (LTD) across a range of stimulation frequencies. Available data are compatible with either a downregulation of the mechanisms of LTD or an upregulation of NMDA receptor function in the visual cortex of dark-reared animals. Here, we provide evidence for enhanced NMDA receptor function by showing that deprivation produces a horizontal shift in the frequency-response function, decreasing LTD in response to 1 Hz stimulation, but increasing LTD in response to 0.5 Hz stimulation. In addition, we show that the effects of dark-rearing on the frequency dependence of LTD can be reversed acutely by partial NMDA receptor blockade. Finally, we show that an in vivo manipulation that rapidly downregulates NMDA receptor function in the visual cortex, brief light exposure, also rapidly reverses the effect of dark-rearing on LTD.
authors.affiliation: Howard Hughes Medical Institute and The Picower Center for Learning and Memory, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Benjamin D
authors.initials: BD
authors.lastname: Philpot
authors.forename: Juan S
authors.initials: JS
authors.lastname: Espinosa
authors.forename: Mark F
authors.initials: MF
authors.lastname: Bear
mesh_terms: D000818:Animals; D003624:Darkness; D004558:Electric Stimulation; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D066298:In Vitro Techniques; D036881:Long-Term Synaptic Depression / Q000502:physiology; D009473:Neuronal Plasticity / Q000502:physiology*; D018408:Patch-Clamp Techniques; D010775:Photic Stimulation; D017440:Photoperiod; D051381:Rats; D020318:Rats, Long-Evans; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors / Q000378:metabolism*; D012683:Sensory Deprivation / Q000502:physiology; D014793:Visual Cortex / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*
chemical_list: D018691:Excitatory Amino Acid Antagonists; D016194:Receptors, N-Methyl-D-Aspartate