title: Layer 5 Pyramidal Neurons' Dendritic Remodeling and Increased Microglial Density in Primary Motor Cortex in a Murine Model of Facial Paralysis.
abstract: This work was aimed at characterizing structural changes in primary motor cortex layer 5 pyramidal neurons and their relationship with microglial density induced by facial nerve lesion using a murine facial paralysis model. Adult transgenic mice, expressing green fluorescent protein in microglia and yellow fluorescent protein in projecting neurons, were submitted to either unilateral section of the facial nerve or sham surgery. Injured animals were sacrificed either 1 or 3 weeks after surgery. Two-photon excitation microscopy was then used for evaluating both layer 5 pyramidal neurons and microglia in vibrissal primary motor cortex (vM1). It was found that facial nerve lesion induced long-lasting changes in the dendritic morphology of vM1 layer 5 pyramidal neurons and in their surrounding microglia. Dendritic arborization of the pyramidal cells underwent overall shrinkage. Apical dendrites suffered transient shortening while basal dendrites displayed sustained shortening. Moreover, dendrites suffered transient spine pruning. Significantly higher microglial cell density was found surrounding vM1 layer 5 pyramidal neurons after facial nerve lesion with morphological bias towards the activated phenotype. These results suggest that facial nerve lesions elicit active dendrite remodeling due to pyramidal neuron and microglia interaction, which could be the pathophysiological underpinning of some neuropathic motor sequelae in humans.
authors.affiliation: Behavioral Neurophysiology Laboratory, Universidad Nacional de Colombia, 111321 Bogotá, Colombia ; Department of Molecular Biology of Neuronal Signals, Max-Planck Institute for Experimental Medicine, 37075 Goettingen, Germany.
authors.forename: Diana
authors.initials: D
authors.lastname: Urrego
authors.affiliation: Behavioral Neurophysiology Laboratory, Universidad Nacional de Colombia, 111321 Bogotá, Colombia ; Department of Biology, School of Sciences, Universidad Nacional de Colombia, 111321 Bogotá, Colombia.
authors.forename: Julieta
authors.initials: J
authors.lastname: Troncoso
authors.affiliation: Behavioral Neurophysiology Laboratory, Universidad Nacional de Colombia, 111321 Bogotá, Colombia ; Department of Physiological Sciences, School of Medicine, Universidad Nacional de Colombia, 111321 Bogotá, Colombia.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Múnera
mesh_terms: D000818:Animals; D005154:Facial Nerve / Q000503:physiopathology*; D005158:Facial Paralysis / Q000235:genetics / Q000503:physiopathology*; D006801:Humans; D051379:Mice; D008822:Mice, Transgenic; D017628:Microglia / Q000473:pathology; D009044:Motor Cortex / Q000503:physiopathology*; D055495:Neurogenesis / Q000235:genetics; D009473:Neuronal Plasticity / Q000235:genetics; D017966:Pyramidal Cells / Q000473:pathology*