title: Synaptic organization of thalamocortical axon collaterals in the perigeniculate nucleus and dorsal lateral geniculate nucleus.
abstract: We examined the synaptic targets of large non-gamma-aminobutyric acid (GABA)-ergic profiles that contain round vesicles and dark mitochondria (RLD profiles) in the perigeniculate nucleus (PGN) and the dorsal lateral geniculate nucleus (dLGN). RLD profiles can provisionally be identified as the collaterals of thalamocortical axons, because their ultrastrucure is distinct from all other previously described dLGN inputs. We also found that RLD profiles are larger than cholinergic terminals and contain the type 2 vesicular glutamate transporter. RLD profiles are distributed throughout the PGN and are concentrated within the interlaminar zones (IZs) of the dLGN, regions distinguished by dense binding of Wisteria floribunda agglutinin (WFA). To determine the synaptic targets of thalamocortical axon collaterals, we examined RLD profiles in the PGN and dLGN in tissue stained for GABA. For the PGN, we found that all RLD profiles make synaptic contacts with GABAergic PGN somata, dendrites, and spines. In the dLGN, RLD profiles primarily synapse with GABAergic dendrites that contain vesicles (F2 profiles) and non-GABAergic dendrites in glomerular arrangements that include triads. Occasional synapses on GABAergic somata and proximal dendrites were also observed in the dLGN. These results suggest that correlated dLGN activity may be enhanced via direct synaptic contacts between thalamocortical cells, whereas noncorrelated activity (such as that occurring during binocular rivalry) could be suppressed via thalamocortical collateral input to PGN cells and dLGN interneurons.
authors.affiliation: Department of Anatomical Sciences and Neurobiology, University of Louisville, Louisville, Kentucky 40292, USA. martha.bickford@louisville.edu
authors.forename: Martha E
authors.initials: ME
authors.lastname: Bickford
authors.forename: Haiyang
authors.initials: H
authors.lastname: Wei
authors.forename: Michael A
authors.initials: MA
authors.lastname: Eisenback
authors.forename: Ranida D
authors.initials: RD
authors.lastname: Chomsung
authors.forename: Arkadiusz S
authors.initials: AS
authors.lastname: Slusarczyk
authors.forename: Aygul B
authors.initials: AB
authors.lastname: Dankowsi
mesh_terms: D000818:Animals; D020643:Anterior Thalamic Nuclei / Q000378:metabolism / Q000502:physiology* / Q000648:ultrastructure; D002415:Cats; D002540:Cerebral Cortex / Q000502:physiology*; D005829:Geniculate Bodies / Q000000981:diagnostic imaging / Q000378:metabolism / Q000502:physiology*; D016253:Microscopy, Immunoelectron / Q000379:methods; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009434:Neural Pathways / Q000502:physiology; D009474:Neurons / Q000378:metabolism / Q000648:ultrastructure; D017729:Presynaptic Terminals / Q000378:metabolism / Q000648:ultrastructure; D013569:Synapses / Q000378:metabolism / Q000648:ultrastructure*; D014463:Ultrasonography; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
chemical_list: D009419:Nerve Tissue Proteins; D005680:gamma-Aminobutyric Acid