Journal of Neuroscience, Vol 10, 3814-3822, Copyright © 1990 by Society for Neuroscience
Competitive interactions between neurons making axosomatic contacts in the leech
XN Gu and KJ Muller
Department of Physiology and Biophysics, University of Miami School of Medicine, Florida 33136.
Axons of lateral nociceptive (N) neurons in leech segmental ganglia wrap
certain somata in adjacent ganglia but no somata in their own ganglion. In
adults, the N neurons, which accurately regenerate axosomatic wrappings,
can be induced to sprout in their own ganglion and wrap target homologues
if the ganglion is isolated by cutting the nerve cord. Manipulations that
denervate the new targets without injuring the lateral N cell, including
focal lesions and protease injections into other N cells, also cause
sprouting within 2-4 months. In contrast, cutting the lateral N cell's
axons causes little or no sprouting within the ganglion without
denervation. Therefore, denervation rather than injury accounts for
sprouting within the ganglion. It is concluded that lateral N cells can
wrap somata in their own ganglion that are homologues of their usual
targets, but they are prevented from doing so by axonal wrappings from N
cells in adjacent ganglia.