The goal of this proposal is to characterize the input of long-range amacrine cells to the Y/Alpha subclass of the cat retina. Although physiological responses of Y cells from retinal stimulation outside the receptive field (a recurring misnomer) have been reported for more than thirty years and have been subsequently characterized, its anatomical basis is not understood. The candidate proposes two hypotheses for the anatomical substrate: many neurons that locally pass signals horizontally or a single neuron with a long axon. Based on the latter, experiments are proposed to demonstrate long-range amacrine cells in the cat retina and then to determine if their morphological (light and EM) features and histochemical markers are consistent with the second hypothesis. The results of such experiments would generally add to our knowledge of retinal circuitry and specifically may reveal the morphological basis for visual response modulation by peripheral stimulation. The experiments entail an in vitro cat retinal preparation in which intracellular fills will be made of Alpha ganglion cells (easily localized for injection microscopically because of their large size) and of long- range amacrine cells (identified by their transport of fluorescent beads from a distant retinal infection site). The stated goal is to fill all of the amacrine cell types that send long axons to the area centralis. The candidate fails to describe the criteria to identify and classify amacrine cells into that category. Will displaced amacrine cell types be included? It is also not clear how one knows that all long- range amacrine cell types are injected and how to exclude incompletely filled ganglion cells. This first goal relies heavily on the resolution of the confocal microscope.
The second aim extends the analysis to include electron microscopic confirmation of synaptic connection. This will be a laborious effort process but the structure of the synaptic vesicle may suggest which neurotransmitter is released by the long-range amacrine cell. The third project would be to combine those previous approaches with immunocytochemistry to identify specific neurotransmitter candidates. These latter projects are described clearly and well-justified, assuming the first goal is met.
| Demb, J B; Zaghloul, K; Sterling, P (2001) Cellular basis for the response to second-order motion cues in Y retinal ganglion cells. Neuron 32:711-21 |
| Demb, J B; Zaghloul, K; Haarsma, L et al. (2001) Bipolar cells contribute to nonlinear spatial summation in the brisk-transient (Y) ganglion cell in mammalian retina. J Neurosci 21:7447-54 |
| Demb, J B; Haarsma, L; Freed, M A et al. (1999) Functional circuitry of the retinal ganglion cell's nonlinear receptive field. J Neurosci 19:9756-67 |
