title: Effects of the Concomitant Activation of ON and OFF Retinal Ganglion Cells on the Visual Thalamus: Evidence for an Enhanced Recruitment of GABAergic Cells.
abstract: A fundamental question in vision neuroscience is how parallel processing of Retinal Ganglion Cell (RGC) signals is integrated at the level of the visual thalamus. It is well-known that parallel ON-OFF pathways generate output signals from the retina that are conveyed to the dorsal lateral geniculate nucleus (dLGN). However, it is unclear how these signals distribute onto thalamic cells and how these two pathways interact. Here, by electrophysiological recordings and c-Fos expression analysis, we characterized the effects of pharmacological manipulations of the retinal circuit aimed at inducing either a selective activation of a single pathway, OFF RGCs [intravitreal L-(+)-2-Amino-4-phosphonobutyric, L-AP4] or an unregulated activity of all classes of RGCs (intravitreal 4-Aminopyridine, 4-AP). In in vivo experiments, the analysis of c-Fos expression in the dLGN showed that these two manipulations recruited active cells from the same area, the lateral edge of the dLGN. Despite this similarity, the unregulated co-activation of both ON and OFF pathways by 4-AP yielded a much stronger recruitment of GABAergic interneurons in the dLGN when compared to L-AP4 pure OFF activation. The increased activation of an inhibitory thalamic network by a high level of unregulated discharge of ON and OFF RGCs might suggest that cross-inhibitory pathways between opposing visual channels are presumably replicated at multiple levels in the visual pathway, thus increasing the filtering ability for non-informative or noisy visual signals.
authors.affiliation: Neurobiology of Learning Unit, Division of Neuroscience, Scientific Institute San Raffaele Milan, Italy ; Università Vita-Salute San Raffaele Milan, Italy ; Ophthalmology, Azienda Ospedaliera San Paolo Milan, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Montesano
authors.affiliation: Neurobiology of Learning Unit, Division of Neuroscience, Scientific Institute San Raffaele Milan, Italy ; Università Vita-Salute San Raffaele Milan, Italy.
authors.forename: Marcello
authors.initials: M
authors.lastname: Belfiore
authors.affiliation: Neurobiology of Learning Unit, Division of Neuroscience, Scientific Institute San Raffaele Milan, Italy ; Università Vita-Salute San Raffaele Milan, Italy.
authors.forename: Maddalena
authors.initials: M
authors.lastname: Ripamonti
authors.affiliation: Neurobiology of Learning Unit, Division of Neuroscience, Scientific Institute San Raffaele Milan, Italy ; Università Vita-Salute San Raffaele Milan, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Arena
authors.affiliation: Neurobiology of Learning Unit, Division of Neuroscience, Scientific Institute San Raffaele Milan, Italy ; Università Vita-Salute San Raffaele Milan, Italy.
authors.forename: Jacopo
authors.initials: J
authors.lastname: Lamanna
authors.affiliation: Neurobiology of Learning Unit, Division of Neuroscience, Scientific Institute San Raffaele Milan, Italy ; Università Vita-Salute San Raffaele Milan, Italy.
authors.forename: Mattia
authors.initials: M
authors.lastname: Ferro
authors.affiliation: Neurobiology of Learning Unit, Division of Neuroscience, Scientific Institute San Raffaele Milan, Italy.
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Zimarino
authors.affiliation: Neurobiology of Learning Unit, Division of Neuroscience, Scientific Institute San Raffaele Milan, Italy ; Università Vita-Salute San Raffaele Milan, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Ambrosi
authors.affiliation: Neurobiology of Learning Unit, Division of Neuroscience, Scientific Institute San Raffaele Milan, Italy ; Università Vita-Salute San Raffaele Milan, Italy.
authors.forename: Antonio
authors.initials: A
authors.lastname: Malgaroli
mesh_terms: D015761:4-Aminopyridine / Q000494:pharmacology; D000200:Action Potentials; D000613:Aminobutyrates / Q000494:pharmacology; D000818:Animals; D005074:Evoked Potentials, Visual; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D059330:GABAergic Neurons / Q000502:physiology*; D007395:Interneurons / Q000502:physiology; D008297:Male; D008959:Models, Neurological; D009010:Monte Carlo Method; D010775:Photic Stimulation; D026902:Potassium Channel Blockers / Q000494:pharmacology; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D017207:Rats, Sprague-Dawley; D012165:Retinal Ganglion Cells / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D012815:Signal Processing, Computer-Assisted; D013788:Thalamus / Q000502:physiology*; D046509:Tissue Culture Techniques; D014795:Visual Pathways / Q000187:drug effects / Q000502:physiology*; D014796:Visual Perception / Q000187:drug effects / Q000502:physiology*
chemical_list: D000613:Aminobutyrates; D018690:Excitatory Amino Acid Agonists; D026902:Potassium Channel Blockers; D016760:Proto-Oncogene Proteins c-fos; D015761:4-Aminopyridine; C012729:2-amino-4-phosphonobutyric acid
keywords: 4-AP; 4-aminopyridine; NeuN; c-Fos; dLGN; inhibitory neurons; retina; visual thalamus