Journal of Neuroscience, Vol 3, 924-932, Copyright © 1983 by Society for Neuroscience
Competence to form electrical connections is restricted to growing neurites in the snail, Helisoma
RD Hadley and SB Kater
Identified neurons of the snail, Helisoma, undergo extensive remodeling in
response to axotomy, including the formation of specific sets of novel
electrical connections. This communication addresses the question of why,
under the conditions employed, some neurons readily form new connections
with a single "test" neurons, whereas others do not. The present
experiments are a test of the hypothesis that, for these adult neurons,
competence to form electrical connections is restricted to pairs of neurons
with interacting regions of active outgrowth. Morphological observations
demonstrated profuse overlapping outgrowth from neurons which formed
electrical connections, whereas neurons which did not connect displayed no
simultaneous new outgrowth, although there could be regions of physical
overlap or proximity. The causal relationship between growth and the
ability to form new connections was tested more directly by two means: (1)
Previously nonconnecting neurons were recruited into the connectivity
pattern by axotomy-induced growth. (2) Previously connecting neurons did
not connect when they were not induced to grow. Thus, growth or lack of
growth is an effective discriminator for determining specific sets of
interconnected neurons.