Meeting Abstract

P3.101  Wednesday, Jan. 6  Visualizing electrical connections between sensory neurons in two leech species, Hirudo verbana and Macrobdella decora. REES, S.R.*; BALTZLEY, M.J.; St. Mary’s College of Maryland; St. Mary’s College of Maryland sdrees@smcm.edu

The leech Hirudo verbana has four pressure mechanosensory neurons (P cells) in each midbody ganglion. Previous experiments indicate that there is weak electrical coupling between P cells in both H. verbana and the leech Macrobdella decora. To visualize this electrical coupling, we injected neurobiotin, a small molecule which can pass through gap junctions, into the P cells of adult H. verbana and M. decora. We visualized the neurobiotin by conjugating it with streptavidin-Cy3. The injections failed to show dye-coupling between P cells and any other neurons in adult H. verbana. Injections in adult M. decora showed P cells dye-coupled to other neurons within isolated ganglia, but not to other P cells. Because our dye-coupling results were inconsistent with those of previous experiments, we hypothesized that the neurobiotin may not pass between the cells if the gap junctions are a great distance from the soma, which may prevent neurobiotin from diffusing from the injected P cell soma to another P cell soma. Therefore, we also injected neurobiotin into P cells of juvenile H. verbana, which have smaller midbody ganglia. Similar to our results with adult M. decora, the P cells were dye-coupled to other neurons within isolated ganglia, but not to other P cells. There are several alternative hypotheses for our results. It is possible that the weak electrical coupling is due to a small number of gap junctions connecting the cells, preventing enough neurobiotin from passing to the coupled soma, or that the P cells are connected electrically through an interneuron, indicating that maybe enough neurobiotin didn’t pass through to secondarily coupled-P cells.