title: Donor-recipient interconnections between giant nerve fibers in transplanted ventral nerve cords of earthworms.
abstract: Twelve segments of ventral nerve cord (VNC) from donor earthworms, Eisenia foetida, were transplanted into recipient worms from which a comparable length of VNC had been removed. Within the first few days after transplantation, bud-like formations, containing outgrowths of the giant nerve fibers, were evident at the ends of transplanted and recipient VNC. Morphological and electrophysiological evidence indicated that by 4-10 days after transplantation, medial (MGF) and lateral (LGF) giant fibers within the transplanted VNC formed cell-specific connections with their counterparts in the recipient VNC. Although the diameters of the giant fiber connections in the transplant-recipient junctions were often larger than normal, spike conduction across the junction was initially slow (approximately 1.0 m/s) but gradually increased over the next 2-3 weeks. Within the transplant, giant fibers were initially normal in appearance, but spike conduction was slow (1-2 m/s). During the next few weeks velocities increased by as much as fourfold and then stabilized for the next several months. However, by 4-5 weeks after transplantation, giant fiber morphology within the transplant was altered significantly, as indicated by the formation of numerous branch-like extensions along the length of each giant fiber. By 9-10 months there were further morphological changes in the transplant, as indicated by decreased branching of the giant fibers and altered neuropile. Despite these morphological changes, through-conduction of giant fiber spikes remained reliable.
mesh_terms: D000818:Animals; D004594:Electrophysiology; D005071:Evoked Potentials; D009412:Nerve Fibers / Q000502:physiology*; D009416:Nerve Regeneration; D009417:Nerve Tissue / Q000637:transplantation*; D009420:Nervous System / Q000033:anatomy & histology*; D009431:Neural Conduction; D009835:Oligochaeta / Q000502:physiology*; D013997:Time Factors