Effect of bilateral nerve injury on the migration of labelled mononuclear cells to hypoglossal nuclei.

Whether cells responding to injury in the central nervous system are of local or hematogenous origin is still a question that has not been answered unequivocally, although ample evidence in favor of a dual origin exists. In the present investigation, mononuclear blood cells were labelled with 3HT one day before left hypoglossal nerve injury. In addition to the initial injury, some of the animals received an injury of the right nerve at a later time. The fate of labelled cells responding to the initial injury when a second injury was made was studied. With two lesions the total number of labelled cells responding was twice the number present with a single lesion at the period of peak response. This was more than could be accounted for by simple migration from left to right. The data presented suggest that mitosis and migration of cells present at the initial lesion accounted for part of the increased number of cells. The possibility that some of the cells responding to the second injury were of recent hematogenous origin was not ruled out.