S100β promotes the extension of microtubule associated protein2 (MAP2)- immunoreactive neurites retracted after colchicine treatment in rat spinal cord culture

S100β, a glial derived calcium-binding protein with neurotrophic activity in the central nervous system, stimulates neurite extension of fetal raphe, cortex, spinal cord, and dorsal root ganglion neurons. The effects of S100β on neurite length and microtubule associated protein2 (MAP2) immunoreactivity (IR) after microtubule disruption with colchicine were investigated in primary rat spinal cord culture. The incubation with S100β (20 ng/ml) for 3 h after exposure to colchicine (10^-6 M) for 30 min altered the distribution of MAP2-IR. The length of MAP2-IR neurites increased by 65% compared to that in colchicine treatment alone. MAP2-IR intensity in the cell body was reduced by 26% compared to that in colchicine treatment alone. These results indicate that neurites shrink when the microtubular cytoskeletal system is disrupted and S100β rapidly promotes re-assembly and/or stabilization.