The effects of multiple sequential episodes of demyelination in the sciatic nerve of the mouse.

Intraneural injections of lysophosphatidyl choline were used to examine the effects of multiple episodes of demyelination and repair in the sciatic nerves of adult mice. It was found that the early phases of repair, from initiation of myelinolysis to the appearance of promyelinated fibres, were achieved more rapidly in multiple-injected nerves than in single-injected nerves. However, this lead was temporary, since subsequent remyelination was delayed in the multiple-injected nerves until several days after it had been established in most single-demyelinated nerves. Cell-mediated demyelination was seen in multiple-injected nerves, but never in single-injected nerves. The results are discussed in terms of a the contribution of supernumerary Schwann cells to the acute stage of the programme of cellular repair; and b the possibility that the 'normal' response to an injection of LPC in a nerve which has previously undergone several episodes of demyelination is exacerbated by a local and self-limiting immune-mediated reaction.