title: Differential depression of inhibitory synaptic responses in feedforward and feedback circuits between different areas of mouse visual cortex.
abstract: Recordings of synaptic responses of pyramidal neurons to feedback (FB) inputs from higher to lower areas of visual cortex show that excitatory synaptic responses are only weakly opposed by disynaptic inhibition. Whether weak inhibition is preserved at high frequencies remains unknown. Whole-cell recordings were performed in pyramidal cells of mouse visual cortex to study the frequency dependence of excitatory and inhibitory postsynaptic currents (EPSCs, IPSCs) elicited by feedforward (FF) input from the primary visual cortex (V1) to the higher lateromedial area (LM) and by FB input from the LM to V1. EPSCs showed similar frequency dependencies in FF and FB pathways; the amplitudes decreased during stimulus trains, and the depression was larger at higher frequencies. IPSCs decreased during repetitive stimulation, and the depression increased at higher frequencies. At >20 Hz, the depression of IPSCs in the FB pathway was greater than in the FF pathway. Thus, unlike FF circuits, FB circuits provide balanced excitatory and inhibitory inputs across a wide range of frequencies. This property was shown to be critically important in cortical circuits that modulate the gain of pyramidal cell firing (Chance et al. [2002] Neuron 35:773-782).
authors.affiliation: Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
authors.forename: Hongwei
authors.initials: H
authors.lastname: Dong
authors.forename: Zhenwei
authors.initials: Z
authors.lastname: Shao
authors.forename: Jeanne M
authors.initials: JM
authors.lastname: Nerbonne
authors.forename: Andreas
authors.initials: A
authors.lastname: Burkhalter
mesh_terms: D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D001640:Bicuculline / Q000494:pharmacology; D048429:Cell Size; D004558:Electric Stimulation / Q000379:methods; D005071:Evoked Potentials / Q000502:physiology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005246:Feedback / Q000502:physiology*; D018756:GABA Antagonists / Q000494:pharmacology; D066298:In Vitro Techniques; D008239:Lysine / Q000031:analogs & derivatives* / Q000378:metabolism; D008564:Membrane Potentials / Q000502:physiology / Q000528:radiation effects; D051379:Mice; D008810:Mice, Inbred C57BL; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D009434:Neural Pathways / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D018408:Patch-Clamp Techniques / Q000379:methods; D017966:Pyramidal Cells / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D011930:Reaction Time / Q000187:drug effects / Q000528:radiation effects; D013569:Synapses / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D009435:Synaptic Transmission / Q000502:physiology; D014793:Visual Cortex / Q000166:cytology / Q000502:physiology*
chemical_list: D018691:Excitatory Amino Acid Antagonists; D018756:GABA Antagonists; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; C013411:biocytin; D008239:Lysine; D001640:Bicuculline