Worm Breeder's Gazette 8(2): 33

These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.

GABA-like Immunoreactivity in Ascaris Neurons

C.D. Johnson, J. Guastella, A.O.W. Stretton, J. Walrond

Antiserum from: Tim Kingan and Sally Hoskins, Columbia 
University
Idea from: Ed Hedgecock, MRC and Roche Institute of Mol.  Biol.
We have used an antiserum prepared against GABA conjugated with 
glutaraldehyde to BSA (see Storm-Mathisen, Nature 301, 517-520 for 
method) to localize GABA within the Ascaris nervous system.  
Preparations used for staining were collagenased to remove muscle 
cells (see Gazette 7(2), p54), fixed immediately with 2% 
glutaraldehyde, 0.5% formaldehyde for 1 hr, washed and treated with 1% 
ethanolamine, then 3% H2O2/10% methanol before incubation with serum (
overnight at 4 C).  Antibody binding was detected using goat-alpha-
rabbit conjugated to HRP and peroxidase-anti-peroxidase followed by 
staining for HRP using the DAB method.
All of the commissures of VI and DI motorneurons stain intensely, 
whereas none of the DE1, DE2 or DE3 commissures stain.  One 
interesting and unexpected feature of the inhibitory motorneuron 
commissures which the staining revealed, was the consistent occurrence 
of a short branch located in one of the sublateral nerve cords.  Each 
commissure crosses both a (right or left) dorsal sublateral and a 
ventral sublateral nerve cord; VI commissures consistently have 
branches in the dorsal sublateral cord, while DI commissures have 
branches in the ventral sublateral cord.  The function of this branch 
is unclear.
Within the dorsal and ventral nerve cords, the processes of the 
inhibitory motorneurons are also intensely stained; there is no 
observable difference in the intensity of staining of dendritic and 
axonal regions of the neurons.
We have also examined staining in the ganglia which surround the 
nerve ring (NR).  Four large GABA-positive cell bodies are located at 
the margin of the NR: two are lateral, one ventral, one dorsal.  The 
ventral and dorsal cells send a strongly staining process posteriorly 
in their respective nerve cords.  All four cells have larger processes 
in the NR.  These cells resemble the RME (V,D,L,R) neurons of C.  
elegans.There are two small intensely staining cells with cell bodies 
located in the left and right posterior lateral ganglia.  These cells 
send a thin process in the deirid commissure to the ventral cord where 
they turn anteriorly, pass through the ventral ganglia and enter the 
NR.  A likely homologue for these cells in C.  elegans is RMG (L and R)
.  Finally, there is a pair of stained cell bodies in the ventral 
ganglia and another pair in the anterior lateral ganglia.  We also 
find a single stained process in the anterior part of each of the four 
posterior sub-lateral nerve cords.  Although we are not completely 
convinced that these sublateral processes are connected to these 
latter 4 cell bodies, we think that these cells may be equivalent to 
the SIB (VL,VR,DL and DR) neurons of C.  elegans.  A less consistent 
feature has been light staining of a pair of large cell bodies in the 
anterior lateral ganglia.  Whether this is due to endogenous 
peroxidase activity or low levels of GABA-like immunoreactivity 
remains to be determined.