PAR-1 activation by SFLLRNP decreases myelin deposition on lumbar motor neuron axons as assessed with cupric silver staining

Working through protease-activated receptors (PARs), serine proteases have been shown to play important roles in neuronal and glial cell survival during development and in neurodegeneration. Past studies in chick embryos have shown that PAR-1 activation during the period of lumbar motor neuron programmed cell death (PCD) leads to a decreased number of surviving motor neurons by embryonic day 10 (E10). Retrospective analysis of these tissues revealed increased thionin staining in the white matter of these spinal cords, interesting because thionin does not normally stain myelinated areas. We hypothesized that PAR-1 activation decreases myelin deposition in developing spinal cords. To activate PAR-1, embryos were treated with the amino acid sequence SFLLRNP for five consecutive days beginning on E5. Embryos were sacrificed on E10, prepared for histology, and stained with cupric silver. The ventral hemispheres of lumbar sections were examined for the degree of demyelination as characterized by punctate or linear silver markings in the white matter. Experimental embryos were found to exhibit statistically more punctate markings and linear markings. This study shows that in addition to decreasing motor neuron survival, PAR-1 activation potentially decreases the conducting ability and viability of the surviving motor neurons.