Modulation of serotonin 5-HT3 receptor expression in injured adult rat spinal cord motoneurons

The effects of sciatic nerve lesions on the expression of serotonin 5-HT3 receptor (5-HT3R) alpha subunit in motoneurons of the spinal cord was investigated by semi-quantitative immunohistochemistry. Following sciatic nerve crush, a significant reduction in density of staining in motoneurons was observed in longitudinal sections of the ventral horn at 3 and 15 days on the lesioned side when compared to the contralateral side (p<0.01). At 30 days after crush, after completion of sciatic nerve regeneration and reinnervation of peripheral targets, intensity of staining had returned to normal. Conversely, after sciatic nerve cut, a lesion that does not allow for target reinnervation, highly significant reductions were observed at 3, 15, 30 and 45 days. These results suggest a role for functional contacts with muscular targets in the maintenance of 5-HT3R expression in spinal motoneurons.