The effects of injury on individually identified central neurons will be studies in the larval sea lamprey, a primitive vertebrate. The objective is to understand how injured neurons regenerate axons from the correct location on the cell surface following axonal amputation. It is known that these neurons regenerate axons from the correct site (i.e. the stump of the cut axon) when the axon is cut at a point distant from the soma, but regenerate axons at incorrect sites (the dendritic tips) following axotomy close to the soma. In this study, the distribution of subcellular structures that are thought to be important in controlling axonal regeneration (microtubules, microtubule organizing centers, neurofilaments, the Golgi apparatus etc.) will be determined both in intact neurons and at various times following either "close" or "distant" axotomy. Particular attention will focus on changes in these structures that occur early after axotomy and are correlated to changes in the sites of axonal regeneration. The role of microtubules in determining the localization of axonal regeneration will be directly tested by injecting microtubule stabilizing and destabilizing drugs into injured neurons.
