The free living nematode, C. elegans is understood at a level of detail equalled by few other organisms, and much of the cell biology and sequence information is proving of considerable utility in the study of parasitic nematodes. Already, C. elegans provides a convenient vehicle for investigating anthelmintic drug action and resistance mechanisms. Among the ionotropic receptors, with their important roles in the behaviour and development of the organism, are targets for anthelmintics. The subunits of nicotinic acetylcholine receptors of C. elegans form a large and diverse multigene family. Members of this family are among the 11 genes associated with resistance to the anthelmintic drug levamisole.

In addition to the well-studied AII amacrine cell, there is another amacrine cell type participating in the rod pathway of the mammalian retina. In cat, this cell is called the A17 amacrine cell, and in rabbits, it is called the indoleamine-accumulating amacrine cell (S1 and S2); however, the presence of the corresponding cell type has not yet been described in detail for the rat retina. To this end, we injected amacrine cells with Neurobiotin in vertical retinal slices. After histological processing, we were able to reconstruct the morphology of a wide-field amacrine cell which showed characteristics of A17 and S1/S2 amacrine cells. The rat wide-field amacrine cells exhibited the same stratification pattern, their dendrites bore varicosities and ramified in sublamina 5 of the inner plexiform layer (IPL), and they were dye-coupled to other amacrine cells. To determine whether those amacrine cells shared electrophysiological characteristics as well, we performed whole-cell patch-clamp recordings and examined their voltage-activated currents and neurotransmitter-induced currents. We never observed voltage-gated Na+ currents and spike-like potentials upon depolarization by current injection in these cells. We identified GABA- and glycine-sensitive Cl− currents that could be blocked by bicuculline and strychnine, respectively. We also observed kainate- and AMPA-activated currents, which could be inhibited by the application of 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX). Finally, a 400-ms full-field light stimulus was used to characterize the light responses of A17 amacrine cells. The light ON-induced inward current could be suppressed by the application of 2,3-Dioxo-6-nitro-1,2,3,4-tetrahydrobenzo[f]quinoxaline-7-sulphonamide (NBQX), while the majority of the light OFF-induced current was inhibited by bicuculline and reduced to a smaller extent by NBQX. CPP, an NMDA blocker, had no effect on the light response of rat A17 amacrine cells.