Central plasticity in rat trigeminal primary sensory neurons innervating vibrissae after neonatal peripheral nerve injury.

This study was undertaken to investigate whether a neonatal vibrissa lesion in the rat may lead to a central plasticity in undamaged vibrissae innervating primary sensory neurons. One vibrissa follicle was removed on the day of birth. After 3-4 months, choleragenoid-horseradish-peroxidase was injected in an adjacent vibrissa follicle either within the row of the missing follicle or across the rows and in the corresponding contralateral follicle. The trigeminal ganglion and nucleus caudalis was studied following retrograde and transganglionic transport of the tracer. The number of labeled cells was not significantly different on the two sides, whereas the central terminal field of labeling was considerably increased on the side of the lesion, but only when the injected follicle was located in the same row as the missing one. Cortical plasticity after neonatal vibrissae follicle lesions may thus be associated with a corresponding plasticity in primary sensory neurons innervating the vibrissae.