[Peripheral facial nerve lesion induced long-term dendritic retraction in pyramidal cortico-facial neurons].
BACKGROUND
Little evidence is available concerning the morphological modifications of motor cortex neurons associated with peripheral nerve injuries, and the consequences of those injuries on post lesion functional recovery.


OBJECTIVE
Dendritic branching of cortico-facial neurons was characterized with respect to the effects of irreversible facial nerve injury.


METHODS
Twenty-four adult male rats were distributed into four groups: sham (no lesion surgery), and dendritic assessment at 1, 3 and 5 weeks post surgery. Eighteen lesion animals underwent surgical transection of the mandibular and buccal branches of the facial nerve. Dendritic branching was examined by contralateral primary motor cortex slices stained with the Golgi-Cox technique. Layer V pyramidal (cortico-facial) neurons from sham and injured animals were reconstructed and their dendritic branching was compared using Sholl analysis.


RESULTS
Animals with facial nerve lesions displayed persistent vibrissal paralysis throughout the five week observation period. Compared with control animal neurons, cortico-facial pyramidal neurons of surgically injured animals displayed shrinkage of their dendritic branches at statistically significant levels. This shrinkage persisted for at least five weeks after facial nerve injury.


CONCLUSIONS
Irreversible facial motoneuron axonal damage induced persistent dendritic arborization shrinkage in contralateral cortico-facial neurons. This morphological reorganization may be the physiological basis of functional sequelae observed in peripheral facial palsy patients.
Laboratorio de Neurofisiología Comportamental, Departamento de Ciencias Fisiológicas, Facultad de Medicina, Universidad Nacional de Colombia, Bogotá, DC, Colombia.
Diana
D
Urrego
Alejandro
A
Múnera
Julieta
J
Troncoso
D000818:Animals; D003712:Dendrites / Q000473:pathology*; D020220:Facial Nerve Injuries / Q000473:pathology*; D008297:Male; D009044:Motor Cortex / Q000473:pathology*; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors