Changes in sensory and motor neurons populations following LPC-induced sciatic nerve demyelination in rats: A study using CTB retrograde tracing

Numerous studies have reported changes in sensory and motor neurons following nerve injury. However, the alterations in the number and subtypes of these neurons after peripheral nerve demyelination remain unclear. This study examined the sciatic nerve’s sensory and motor functions and demyelination status in rats at days 0, 7, 14, and 28 post-lysolecithin (LPC) injection. Three rats from each group were injected with cholera toxin subunit B (CTB) distal to the demyelinated region, followed by immunofluorescence analysis of sensory and motor neuron changes. Compared to day 0, days 7 and 14 showed a significant decline in mechanical pain thresholds and sciatic nerve function, with substantial demyelination observed. The number of CTB-labeled large and medium-sized sensory neurons decreased, while small sensory neurons remained unchanged. LPC demyelination reduced calcitonin gene-related peptide (CGRP) and isolectin B4 (IB4) positive neurons in the L4-5 dorsal root ganglia, with no changes in neurofilament 200 (NF200) positive neurons. Additionally, alpha motor neurons decreased, but gamma motor neurons were unchanged, with significant microglial activation observed. By day 28, the numbers of medium-sized sensory and alpha motor neurons had nearly returned to baseline. These findings indicate significant changes in sensory and motor neuron populations post-demyelination, potentially contributing to dysfunction in peripheral demyelinating diseases. CTB tracing may effectively evaluate demyelination and remyelination.