Monosynaptic pathway from rat vibrissa motor cortex to facial motor neurons revealed by lentivirus-based axonal tracing

Grinevich, V., Brecht, M., Osten, P. (September 2005) Monosynaptic pathway from rat vibrissa motor cortex to facial motor neurons revealed by lentivirus-based axonal tracing. Journal of Neuroscience, 25 (36). pp. 8250-8. ISSN 0270-6474

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DOI: 10.1523/JNEUROSCI.2235-05.2005


The mammalian motor cortex typically innervates motor neurons indirectly via oligosynaptic pathways. However, evolution of skilled digit movements in humans, apes, and some monkey species is associated with the emergence of abundant monosynaptic cortical projections onto spinal motor neurons innervating distal limb muscles. Rats perform skilled movements with their whiskers, and we examined the possibility that the rat vibrissa motor cortex (VMC) projects monosynaptically onto facial motor neurons controlling the whisker movements. First, single injections of lentiviruses to VMC sites identified by intracortical microstimulations were used to label a distinct subpopulation of VMC axons or presynaptic terminals by expression of enhanced green fluorescent protein (GFP) or GFP-tagged synaptophysin, respectively. Four weeks after the injections, GFP and synaptophysin-GFP labeling of axons and putative presynaptic terminals was detected in the lateral portion of the facial nucleus (FN), in close proximity to motor neurons identified morphologically and by axonal back-labeling from the whisker follicles. The VMC projections were detected bilaterally, with threefold larger density of labeling in the contralateral FN. Next, multiple VMC injections were used to label a large portion of VMC axons, resulting in overall denser but still laterally restricted FN labeling. Ultrastructural analysis of the GFP-labeled VMC axons confirmed the existence of synaptic contacts onto dendrites and somata of FN motor neurons. These findings provide anatomical demonstration of monosynaptic VMC-to-FN pathway in the rat and show that lentivirus-based expression of GFP and GFP-tagged presynaptic proteins can be used as a high-resolution neuroanatomical tracing method.

Item Type: Paper
Additional Information:
Uncontrolled Keywords: Animals Axons physiology ultrastructure virology Electric Stimulation Face innervation Genes Reporter Green Fluorescent Proteins analysis genetics Lentivirus Motor Cortex physiology Motor Neurons physiology Movement Pyramidal Cells physiology Rats Synapses physiology Vibrissae innervation physiology
Subjects: organism description > animal behavior
organism description > virus > lentivirus
organism description > animal behavior > vibrissa motor cortex
CSHL Authors:
Communities: CSHL labs > Osten lab
Depositing User: CSHL Librarian
Date: 7 September 2005
Date Deposited: 13 Jan 2012 15:05
Last Modified: 08 Apr 2013 15:12
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