Journal of Neuroscience, Vol 5, 1-8, Copyright © 1985 by Society for Neuroscience
Identification of excitatory and inhibitory motoneurons in the nematode Ascaris by electrophysiological techniques
JP Walrond, IS Kass, AO Stretton and JE Donmoyer
A physiological preparation in which it is possible to record responses in
muscle to stimulation of single motoneurons of the nematode Ascaris
lumbricoides is described. With this preparation we have determined the
physiological sign (E or I; excitatory or inhibitory) of the neuromuscular
synapses of 21 identified motoneurons--12 are excitatory and 9 inhibitory.
Ascaris motoneurons had previously been classified by morphological
criteria into seven classes (Stretton, A. O. W., R. M. Fishpool, E.
Southgate, J. E. Donmoyer, J. P. Walrond, J. E. R. Moses, and I. S. Kass
(1978) Proc. Natl. Acad. Sci. U. S. A. 75: 3493-3497). Physiological
studies were performed on members of five of these classes. Three classes
of neurons (DE1, DE2, and DE3) are excitatory to dorsal muscle cells. Two
classes (DI and VI) are inhibitory neurons which innervate the dorsal and
ventral muscle cells, respectively. The motoneurons in Caenorhabditis
elegans (White, J. E., E. Southgate, J. N. Thomson, and S. Brenner (1976)
Philos. Trans. R. Soc. Lond. (Biol.) 275: 327-348) can be divided into
seven morphological classes which are very similar to those in Ascaris.
Based upon the structure-function correlation in Ascaris, we have predicted
which motoneurons are excitatory and which are inhibitory in C. elegans.
