Targeted somatosensory stimulation modulates facial nucleus glial responses and promotes functional recovery after facial nerve axotomy in rats

Abstract Peripheral facial nerve injury is accompanied by distal nerve degeneration and glial responses in the facial motor nucleus. This pilot preclinical study compared manual whisker-pad stimulation with mechanical vibrissal brushing after unilateral facial nerve axotomy in rats. Twenty-four rats were randomly assigned to Sham, Axotomy, Axotomy plus manual stimulation, or Axotomy plus mechanical stimulation groups ( n = 6 each), with three intact controls for Western blot. Stimulation was administered three times weekly for seven weeks. Functional recovery was assessed longitudinally; other outcomes were evaluated at eight weeks. Morphological and molecular analyses included three animals per group, and immunofluorescence analyses included six animals per group. Relative to untreated axotomy, manual stimulation was associated with improved facial motor scores, higher compound muscle action potential amplitude, lower electrophysiological degeneration, greater myelinated axon counts and myelin thickness, lower c-Jun, SMAD2 and TLR2 and higher phosphorylated AKT levels, lower Iba-1 and GFAP relative intensities, and higher ChAT-positive motor neuron counts. Although fewer outcomes reached statistical significance with mechanical stimulation, the two modalities did not differ significantly from each other on any measure. These exploratory findings require confirmation in adequately powered studies and establish neither modality superiority nor causality.