title: Y retinal terminals contact interneurons in the cat dorsal lateral geniculate nucleus.
abstract: One of the largest influences on dorsal lateral geniculate nucleus (dLGN) activity comes from interneurons, which use the neurotransmitter gamma-aminobutyric acid (GABA). It is well established that X retinogeniculate terminals contact interneurons and thalamocortical cells in complex synaptic arrangements known as glomeruli. However, there is little anatomical evidence for the involvement of dLGN interneurons in the Y pathway. To determine whether Y retinogeniculate axons contact interneurons, we injected the superior colliculus (SC) with biotinylated dextran amine (BDA) to backfill retinal axons, which also project to the SC. Within the A lamina of the dLGN, this BDA labeling allowed us to distinguish Y retinogeniculate axons from X retinogeniculate axons, which do not project to the SC. In BDA-labeled tissue prepared for electron microscopic analysis, we subsequently used postembedding immunocytochemical staining for GABA to distinguish interneurons from thalamocortical cells. We found that the majority of profiles postsynaptic to Y retinal axons were GABA-negative dendrites of thalamocortical cells (117/200 or 58.5%). The remainder (83/200 or 41.5%) were GABA-positive dendrites, many of which contained vesicles (59/200 or 29.5%). Thus, Y retinogeniculate axons do contact interneurons. However, these contacts differed from X retinogeniculate axons, in that triadic arrangements were rare. This indicates that the X and Y pathways participate in unique circuitries but that interneurons are involved in the modulation of both pathways.
authors.affiliation: Department of Anatomical Sciences and Neurobiology, University of Louisville, School of Medicine, Louisville, Kentucky 40292, USA.
authors.forename: A
authors.initials: A
authors.lastname: Datskovskaia
authors.forename: W B
authors.initials: WB
authors.lastname: Carden
authors.forename: M E
authors.initials: ME
authors.lastname: Bickford
mesh_terms: D000818:Animals; D001369:Axons / Q000502:physiology / Q000648:ultrastructure; D001710:Biotin / Q000031:analogs & derivatives*; D002415:Cats / Q000502:physiology*; D003712:Dendrites / Q000378:metabolism / Q000648:ultrastructure; D003911:Dextrans; D005456:Fluorescent Dyes; D005829:Geniculate Bodies / Q000502:physiology* / Q000648:ultrastructure; D007150:Immunohistochemistry / Q000379:methods; D007395:Interneurons / Q000502:physiology*; D008854:Microscopy, Electron; D009411:Nerve Endings / Q000502:physiology*; D012160:Retina / Q000502:physiology*; D013194:Staining and Labeling; D013477:Superior Colliculi / Q000502:physiology; D009435:Synaptic Transmission / Q000502:physiology; D013788:Thalamus / Q000166:cytology / Q000502:physiology / Q000648:ultrastructure; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
chemical_list: D003911:Dextrans; D005456:Fluorescent Dyes; C076397:biotinylated dextran amine; D005680:gamma-Aminobutyric Acid; D001710:Biotin