REMODELING OF AN INTACT NEURON IN THE CENTRAL-NERVOUS-SYSTEM OF THE LEECH

The regeneration pattern of two identified central neurones was studie d in the leech Hirudo medicinalis. Anterior pagoda (AP) and mechanosen sory touch-sensitive (T) neurones were stained in adult segmental gang lia, maintained in culture for 6-10 days. AP neurones, which normally project only to the contralateral nerve roots, sprouted extensively in all the available nerve paths during regeneration. Mechanosensory T c ells, in the same experimental conditions, showed only a moderate grow th and did not change their normal pattern of axonal projections. The observed differences in the growth pattern might account for the diffe rent electrophysiological responses to axotomy exhibited by the two ty pes of neurone. Interruption of interganglionic connectives induced a moderate and stereotyped remodelling of the morphology of intact AP ne urones, which was reminiscent of that transiently exhibited during emb ryonic development. This response was observed in 25% of the AP neuron es we examined.