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J Comp Neurol. 2017 Jun 1;525(8):1844-1860. doi: 10.1002/cne.24164. Epub 2017 Mar 14.

Kölliker-Fuse GABAergic and glutamatergic neurons project to distinct targets.

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Department of Neurology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts.
Division of Sleep Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts.
Department of Neurology, University of Iowa Hospital and Clinics, Iowa City, Iowa.
Department of Anatomy and Morphological Neuroscience, Shimane University School of Medicine, Izumo, Japan.
V.A. Greater Los Angeles Healthcare System, Los Angeles, California.
Department of Medicine, David Geffen School of Medicine at UCLA, Los Angeles, California.


The Kölliker-Fuse nucleus (KF) is known primarily for its respiratory function as the "pneumotaxic center" or "pontine respiratory group." Considered part of the parabrachial (PB) complex, KF contains glutamatergic neurons that project to respiratory-related targets in the medulla and spinal cord (Yokota, Oka, Tsumori, Nakamura, & Yasui, 2007). Here we describe an unexpected population of neurons in the caudal KF and adjacent lateral crescent subnucleus (PBlc), which are γ-aminobutyric acid (GABA)ergic and have an entirely different pattern of projections than glutamatergic KF neurons. First, immunofluorescence, in situ hybridization, and Cre-reporter labeling revealed that many of these GABAergic neurons express FoxP2 in both rats and mice. Next, using Cre-dependent axonal tracing in Vgat-IRES-Cre and Vglut2-IRES-Cre mice, we identified different projection patterns from GABAergic and glutamatergic neurons in this region. GABAergic neurons in KF and PBlc project heavily and almost exclusively to trigeminal sensory nuclei, with minimal projections to cardiorespiratory nuclei in the brainstem, and none to the spinal cord. In contrast, glutamatergic KF neurons project heavily to the autonomic, respiratory, and motor regions of the medulla and spinal cord previously identified as efferent targets mediating KF cardiorespiratory effects. These findings identify a novel, GABAergic subpopulation of KF/PB neurons with a distinct efferent projection pattern targeting the brainstem trigeminal sensory system. Rather than regulating breathing, we propose that these neurons influence vibrissal sensorimotor function.


FoxP2; PBel; RRID: AB_10015246; RRID: AB_2107107; RRID: AB_2107133; parabrachial; respiratory; trigeminal; whisking

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