GLIAL-CELL REACTIONS IN THE SPINAL-CORD AFTER SENSORY NERVE-STIMULATION ARE ASSOCIATED WITH AXONAL INJURY

Astroglial and microglial reactions in the dorsal and ventral horns of the adult rat spinal cord were studied after graded electrical stimul ation of the rat sciatic nerve and after topical application of mustar d oil to the hindlimb foot. Antibodies to glial fibrillary acidic prot ein and complement receptor 3 (OX-42) were used as markers for astrogl ia and microglia, respectively. The results showed that electrical ner ve stimulation resulted in increased immunoreactivity for GFAP and OX- 42 in the spinal cord dorsal and ventral horns only after the use of s timulation strengths which were associated with nerve fiber degenerati on in the stimulated nerve. Application of mustard oil to the foot cau sed no changes in GFAP or OX-42 immunoreactivity. These findings indic ate that peripheral nerve stimulation in itself is insufficient to ind uce astroglial and microglial responses in the spinal cord. The signal (s) mediating these responses, regularly seen after nerve injury, are therefore most probably not related to the afferent barrage of action potentials evoked by the injury.