title: Collateral projection from the locus coeruleus to whisker-related sensory and motor brain regions of the rat.
abstract: The primary goal of this study was to examine whether the locus coeruleus (LC) provides collateral projections to whisker-related, sensorimotor brain regions. After injections of retrograde tracers into the primary sensory (S1) barrel field/primary whisker motor (M1) cortices, ventroposteromedial (VPM)/ventrolateral (VL) thalamic nuclei, or principal sensory trigeminal (Pr5)/facial motor (Mo7) nuclei, the distribution of double-labeled neurons within the LC was examined. Our observations indicated that a large number of individual LC cells provided axon collaterals to S1-M1 or VPM-VL regions, whereas only a few projected to Pr5-Mo7 nuclei. The laterality and the distribution of dual-projecting LC neurons were as follows. 1) The neurons projecting to the S1-M1 cortices were predominantly ipsilateral (96% +/- 0.7%). Labeled neurons were located ventrally at the rostral pole but were evenly distributed along the dorsoventral aspect of the principal LC. 2) The cells projecting to the VPM-VL nuclei were bilateral, with ipsilateral (68% +/- 2.3%) dominance. Neurons were observed at the rostrocaudal extent of the LC, where the labeling was most pronounced at the ventral, principal LC. 3) The neurons projecting to the Pr5-Mo7 regions exhibited slightly contralateral (56% +/- 2.9%) dominance, where labeled cells were confined within the ventral margin of the principal subdivision. Taken together, the present observations demonstrate that each subdivision of the LC possesses a differential functional organization with respect to its collateral projection to whisker-related sensorimotor targets, suggesting that the nucleus might play a modulatory role in vibrissal sensorimotor integration that allows the guidance of behavioral action essential for the survival of the animal.
authors.affiliation: Department of Anatomy, College of Medicine, Konkuk University, Hwayang-Dong, Gwangjin-Gu, Seoul, Korea.
authors.forename: Sat-Byol
authors.initials: SB
authors.lastname: Lee
authors.forename: Suk K
authors.initials: SK
authors.lastname: Beak
authors.forename: Seung H
authors.initials: SH
authors.lastname: Park
authors.forename: Barry D
authors.initials: BD
authors.lastname: Waterhouse
authors.forename: Hyun S
authors.initials: HS
authors.lastname: Lee