Journal of Neuroscience, Vol 7, 223-235, Copyright © 1987 by Society for Neuroscience
GABA-immunoreactivity in inhibitory motor neurons of the nematode Ascaris
CD Johnson and AO Stretton
We have used GABA-specific antisera to detect GABA-immunoreactivity in the
motor neurons of the ventral nerve cord of Ascaris. We find that a subset
of the individually identifiable commissures of motor neurons is
specifically stained. On the basis of the location and morphology of
stained commissures and of the location of stained cell bodies in the
ventral nerve cord, we conclude that the labeled neurons comprise all
members of the VI (inhibiting ventral muscle; 13 cells) and DI (inhibiting
dorsal muscle; 6 cells) classes of inhibitory motor neurons (Stretton et
al., 1978; Walrond et al., 1985). This result supports previous suggestions
(e.g., del Castillo et al., 1964b) that GABA is the neurotransmitter
released by the inhibitory motor neurons of nematodes. In the anterior part
of the animal, the inhibitory motor neuron commissures have small branches
in the sublateral nerve cords that have not been previously described: VI
commissures have dorsal sublateral branches, while DI cells have ventral
branches. Posterior VI neurons have branches in the lateral nerve cords.