title: Local connections of excitatory neurons to corticothalamic neurons in the rat barrel cortex.
abstract: Corticothalamic projection neurons in the cerebral cortex constitute an important component of the thalamocortical reciprocal circuit, an essential input/output organization for cortical information processing. However, the spatial organization of local excitatory connections to corticothalamic neurons is only partially understood. In the present study, we first developed an adenovirus vector expressing somatodendritic membrane-targeted green fluorescent protein. After injection of the adenovirus vector into the ventrobasal thalamic complex, a band of layer (L) 6 corticothalamic neurons in the rat barrel cortex were retrogradely labeled. In addition to their cell bodies, fine dendritic spines of corticothalamic neurons were well visualized without the labeling of their axon collaterals or thalamocortical axons. In cortical slices containing retrogradely labeled L6 corticothalamic neurons, we intracellularly stained single pyramidal/spiny neurons of L2-6. We examined the spatial distribution of contact sites between the local axon collaterals of each pyramidal neuron and the dendrites of corticothalamic neurons. We found that corticothalamic neurons received strong and focused connections from L4 neurons just above them, and that the most numerous nearby and distant sources of local excitatory connections to corticothalamic neurons were corticothalamic neurons themselves and L6 putative corticocortical neurons, respectively. These results suggest that L4 neurons may serve as an important source of local excitatory inputs in shaping the cortical modulation of thalamic activity.
authors.affiliation: Department of Morphological Brain Science, Graduate School of Medicine, Kyoto University, Kyoto 606-8501, Japan.
authors.forename: Yasuhiro R
authors.initials: YR
authors.lastname: Tanaka
authors.forename: Yasuyo H
authors.initials: YH
authors.lastname: Tanaka
authors.forename: Michiteru
authors.initials: M
authors.lastname: Konno
authors.forename: Fumino
authors.initials: F
authors.lastname: Fujiyama
authors.forename: Takahiro
authors.initials: T
authors.lastname: Sonomura
authors.forename: Keiko
authors.initials: K
authors.lastname: Okamoto-Furuta
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kameda
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Hioki
authors.forename: Takahiro
authors.initials: T
authors.lastname: Furuta
authors.forename: Kouichi C
authors.initials: KC
authors.lastname: Nakamura
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kaneko
mesh_terms: D000818:Animals; D001369:Axons / Q000502:physiology; D008297:Male; D009434:Neural Pathways / Q000166:cytology / Q000502:physiology; D056325:Neuronal Tract-Tracers; D009474:Neurons / Q000166:cytology / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D013003:Somatosensory Cortex / Q000166:cytology / Q000502:physiology*; D013788:Thalamus / Q000166:cytology / Q000502:physiology*
chemical_list: D056325:Neuronal Tract-Tracers