Ligand-gated chloride channels (LGCCs) are key components of the nervous system of parasitic nematodes and important targets for anthelmintics. Here, we describe the isolation and characterization of a novel member of the LGCC gene family (HcLGCC1) from the parasitic nematode Haemonchus contortus. Sequence analysis revealed that the channel subunit encoded by HcLGCC1 is anion selective and a member of a group of channels characterized as having two Cys-loops in the N-terminal ligand-binding domain†. Although the overall function of HcLGCC1 is presently unknown, the gene may play a key role in the early developmental stages of the parasite. Further investigations into the function of LGCCs, such as HcLGCC1, in parasitic nematodes should have implications for the discovery of new anthelmintic targets.

The inhibitory neurotransmitter gamma aminobutyric acid (GABA) has been shown to influence the responses of ganglion cells in the mammalian retina. Consistently, GABAA receptor subunits have been localized to different ganglion cell types. In this study, the distribution of the α1 subunit of the GABAA receptor on the dendrites of midget and parasol ganglion cells was investigated quantitatively in the retina of a New World monkey, the marmoset. Ganglion cells were injected with Neurobiotin in a live in vitro retinal whole-mount preparation. Retinal pieces were then processed with an antibody against the α1 subunit of the GABAA receptor. Strong punctate immunoreactivity indicative of synaptic localization is present in the ON and OFF sublamina of the inner plexiform layer. Many of the immunoreactive puncta coincide with the dendrites of both midget and parasol ganglion cells. Immunoreactive puncta are present on distal and proximal dendrites of ON and OFF cells of both ganglion cell types. On average, parasol cells show a slight increase in the spatial density of immunoreactive puncta with distance from the soma, whereas the density of immunoreactive puncta on midget cells stays even. Parasol ganglion cells show a slightly higher average density of immunoreactive puncta (0.083 puncta/μm dendrite) than midget cells (0.054 puncta/μm dendrite).

Glycine is a major inhibitory neurotransmitter in the mammalian retina and has been shown to influence the responses of ganglion cells. Midget and parasol ganglion cells serve distinct physiological roles in the primate retina and show differences in their response characteristics to light stimuli. In the present study, we addressed the question of whether the expression of glycine receptors differs in midget and parasol ganglion cells. Ganglion cells in the retinae of marmoset and macaque monkeys were injected with Neurobiotin in a live in vitro retinal whole-mount preparation. Retinal pieces were then processed with an antibody against the α1 subunit of the glycine receptor. Strong punctate immunoreactivity indicative of synaptic localization is present in the ON and OFF sublamina of the inner plexiform layer. Many of the immunoreactive puncta coincide with the dendrites of both midget and parasol ganglion cells. Immunoreactive puncta are present on distal and proximal dendrites of ON and OFF cells. These results suggest that ON and OFF midget and parasol cells do not differ with respect to the distribution of the α1 subunit of the glycine receptor.