Further evidence in support of a causal link between calcium signaling and remyelination is provided by experiments showing that rHIgM22 elicits a transient elevation in intracellular calcium in CG4 cells, a model of premyelinating oligodendrocytes (Howe et al., 2004) . As with primary oligodendrocytes, we found that this calcium signal was dependent on the influx of extracellular calcium through AMPA receptor calcium channels.